1# SPDX-License-Identifier: GPL-2.0+ 2# 3# (C) Copyright 2000 - 2013 4# Wolfgang Denk, DENX Software Engineering, wd@denx.de. 5 6Summary: 7======== 8 9This directory contains the source code for U-Boot, a boot loader for 10Embedded boards based on PowerPC, ARM, MIPS and several other 11processors, which can be installed in a boot ROM and used to 12initialize and test the hardware or to download and run application 13code. 14 15The development of U-Boot is closely related to Linux: some parts of 16the source code originate in the Linux source tree, we have some 17header files in common, and special provision has been made to 18support booting of Linux images. 19 20Some attention has been paid to make this software easily 21configurable and extendable. For instance, all monitor commands are 22implemented with the same call interface, so that it's very easy to 23add new commands. Also, instead of permanently adding rarely used 24code (for instance hardware test utilities) to the monitor, you can 25load and run it dynamically. 26 27 28Status: 29======= 30 31In general, all boards for which a default configuration file exists in the 32configs/ directory have been tested to some extent and can be considered 33"working". In fact, many of them are used in production systems. 34 35In case of problems you can use 36 37 scripts/get_maintainer.pl <path> 38 39to identify the people or companies responsible for various boards and 40subsystems. Or have a look at the git log. 41 42 43Where to get help: 44================== 45 46In case you have questions about, problems with or contributions for 47U-Boot, you should send a message to the U-Boot mailing list at 48<u-boot@lists.denx.de>. There is also an archive of previous traffic 49on the mailing list - please search the archive before asking FAQ's. 50Please see https://lists.denx.de/pipermail/u-boot and 51https://marc.info/?l=u-boot 52 53Where to get source code: 54========================= 55 56The U-Boot source code is maintained in the Git repository at 57https://source.denx.de/u-boot/u-boot.git ; you can browse it online at 58https://source.denx.de/u-boot/u-boot 59 60The "Tags" links on this page allow you to download tarballs of 61any version you might be interested in. Official releases are also 62available from the DENX file server through HTTPS or FTP. 63https://ftp.denx.de/pub/u-boot/ 64ftp://ftp.denx.de/pub/u-boot/ 65 66 67Where we come from: 68=================== 69 70- start from 8xxrom sources 71- create PPCBoot project (https://sourceforge.net/projects/ppcboot) 72- clean up code 73- make it easier to add custom boards 74- make it possible to add other [PowerPC] CPUs 75- extend functions, especially: 76 * Provide extended interface to Linux boot loader 77 * S-Record download 78 * network boot 79 * ATA disk / SCSI ... boot 80- create ARMBoot project (https://sourceforge.net/projects/armboot) 81- add other CPU families (starting with ARM) 82- create U-Boot project (https://sourceforge.net/projects/u-boot) 83- current project page: see https://www.denx.de/wiki/U-Boot 84 85 86Names and Spelling: 87=================== 88 89The "official" name of this project is "Das U-Boot". The spelling 90"U-Boot" shall be used in all written text (documentation, comments 91in source files etc.). Example: 92 93 This is the README file for the U-Boot project. 94 95File names etc. shall be based on the string "u-boot". Examples: 96 97 include/asm-ppc/u-boot.h 98 99 #include <asm/u-boot.h> 100 101Variable names, preprocessor constants etc. shall be either based on 102the string "u_boot" or on "U_BOOT". Example: 103 104 U_BOOT_VERSION u_boot_logo 105 IH_OS_U_BOOT u_boot_hush_start 106 107 108Software Configuration: 109======================= 110 111Selection of Processor Architecture and Board Type: 112--------------------------------------------------- 113 114For all supported boards there are ready-to-use default 115configurations available; just type "make <board_name>_defconfig". 116 117Example: For a TQM823L module type: 118 119 cd u-boot 120 make TQM823L_defconfig 121 122Note: If you're looking for the default configuration file for a board 123you're sure used to be there but is now missing, check the file 124doc/README.scrapyard for a list of no longer supported boards. 125 126Sandbox Environment: 127-------------------- 128 129U-Boot can be built natively to run on a Linux host using the 'sandbox' 130board. This allows feature development which is not board- or architecture- 131specific to be undertaken on a native platform. The sandbox is also used to 132run some of U-Boot's tests. 133 134See doc/arch/sandbox/sandbox.rst for more details. 135 136 137Board Initialisation Flow: 138-------------------------- 139 140This is the intended start-up flow for boards. This should apply for both 141SPL and U-Boot proper (i.e. they both follow the same rules). 142 143Note: "SPL" stands for "Secondary Program Loader," which is explained in 144more detail later in this file. 145 146At present, SPL mostly uses a separate code path, but the function names 147and roles of each function are the same. Some boards or architectures 148may not conform to this. At least most ARM boards which use 149CONFIG_SPL_FRAMEWORK conform to this. 150 151Execution typically starts with an architecture-specific (and possibly 152CPU-specific) start.S file, such as: 153 154 - arch/arm/cpu/armv7/start.S 155 - arch/powerpc/cpu/mpc83xx/start.S 156 - arch/mips/cpu/start.S 157 158and so on. From there, three functions are called; the purpose and 159limitations of each of these functions are described below. 160 161lowlevel_init(): 162 - purpose: essential init to permit execution to reach board_init_f() 163 - no global_data or BSS 164 - there is no stack (ARMv7 may have one but it will soon be removed) 165 - must not set up SDRAM or use console 166 - must only do the bare minimum to allow execution to continue to 167 board_init_f() 168 - this is almost never needed 169 - return normally from this function 170 171board_init_f(): 172 - purpose: set up the machine ready for running board_init_r(): 173 i.e. SDRAM and serial UART 174 - global_data is available 175 - stack is in SRAM 176 - BSS is not available, so you cannot use global/static variables, 177 only stack variables and global_data 178 179 Non-SPL-specific notes: 180 - dram_init() is called to set up DRAM. If already done in SPL this 181 can do nothing 182 183 SPL-specific notes: 184 - you can override the entire board_init_f() function with your own 185 version as needed. 186 - preloader_console_init() can be called here in extremis 187 - should set up SDRAM, and anything needed to make the UART work 188 - there is no need to clear BSS, it will be done by crt0.S 189 - for specific scenarios on certain architectures an early BSS *can* 190 be made available (via CONFIG_SPL_EARLY_BSS by moving the clearing 191 of BSS prior to entering board_init_f()) but doing so is discouraged. 192 Instead it is strongly recommended to architect any code changes 193 or additions such to not depend on the availability of BSS during 194 board_init_f() as indicated in other sections of this README to 195 maintain compatibility and consistency across the entire code base. 196 - must return normally from this function (don't call board_init_r() 197 directly) 198 199Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at 200this point the stack and global_data are relocated to below 201CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of 202memory. 203 204board_init_r(): 205 - purpose: main execution, common code 206 - global_data is available 207 - SDRAM is available 208 - BSS is available, all static/global variables can be used 209 - execution eventually continues to main_loop() 210 211 Non-SPL-specific notes: 212 - U-Boot is relocated to the top of memory and is now running from 213 there. 214 215 SPL-specific notes: 216 - stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and 217 CONFIG_SYS_FSL_HAS_CCI400 218 219 Defined For SoC that has cache coherent interconnect 220 CCN-400 221 222 CONFIG_SYS_FSL_HAS_CCN504 223 224 Defined for SoC that has cache coherent interconnect CCN-504 225 226The following options need to be configured: 227 228- CPU Type: Define exactly one, e.g. CONFIG_MPC85XX. 229 230- Board Type: Define exactly one, e.g. CONFIG_MPC8540ADS. 231 232- 85xx CPU Options: 233 CONFIG_SYS_PPC64 234 235 Specifies that the core is a 64-bit PowerPC implementation (implements 236 the "64" category of the Power ISA). This is necessary for ePAPR 237 compliance, among other possible reasons. 238 239 CONFIG_SYS_FSL_ERRATUM_A004510 240 241 Enables a workaround for erratum A004510. If set, 242 then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and 243 CFG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set. 244 245 CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV 246 CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional) 247 248 Defines one or two SoC revisions (low 8 bits of SVR) 249 for which the A004510 workaround should be applied. 250 251 The rest of SVR is either not relevant to the decision 252 of whether the erratum is present (e.g. p2040 versus 253 p2041) or is implied by the build target, which controls 254 whether CONFIG_SYS_FSL_ERRATUM_A004510 is set. 255 256 See Freescale App Note 4493 for more information about 257 this erratum. 258 259 CFG_SYS_FSL_CORENET_SNOOPVEC_COREONLY 260 261 This is the value to write into CCSR offset 0x18600 262 according to the A004510 workaround. 263 264 CONFIG_SYS_FSL_SINGLE_SOURCE_CLK 265 Single Source Clock is clocking mode present in some of FSL SoC's. 266 In this mode, a single differential clock is used to supply 267 clocks to the sysclock, ddrclock and usbclock. 268 269- Generic CPU options: 270 271 CONFIG_SYS_FSL_DDR 272 Freescale DDR driver in use. This type of DDR controller is 273 found in mpc83xx, mpc85xx as well as some ARM core SoCs. 274 275 CFG_SYS_FSL_DDR_ADDR 276 Freescale DDR memory-mapped register base. 277 278 CONFIG_SYS_FSL_IFC_CLK_DIV 279 Defines divider of platform clock(clock input to IFC controller). 280 281 CONFIG_SYS_FSL_LBC_CLK_DIV 282 Defines divider of platform clock(clock input to eLBC controller). 283 284 CFG_SYS_FSL_DDR_SDRAM_BASE_PHY 285 Physical address from the view of DDR controllers. It is the 286 same as CFG_SYS_DDR_SDRAM_BASE for all Power SoCs. But 287 it could be different for ARM SoCs. 288 289- ARM options: 290 CFG_SYS_EXCEPTION_VECTORS_HIGH 291 292 Select high exception vectors of the ARM core, e.g., do not 293 clear the V bit of the c1 register of CP15. 294 295 COUNTER_FREQUENCY 296 Generic timer clock source frequency. 297 298 COUNTER_FREQUENCY_REAL 299 Generic timer clock source frequency if the real clock is 300 different from COUNTER_FREQUENCY, and can only be determined 301 at run time. 302 303- Linux Kernel Interface: 304 CONFIG_OF_LIBFDT 305 306 New kernel versions are expecting firmware settings to be 307 passed using flattened device trees (based on open firmware 308 concepts). 309 310 CONFIG_OF_LIBFDT 311 * New libfdt-based support 312 * Adds the "fdt" command 313 * The bootm command automatically updates the fdt 314 315 OF_TBCLK - The timebase frequency. 316 317 boards with QUICC Engines require OF_QE to set UCC MAC 318 addresses 319 320 CONFIG_OF_IDE_FIXUP 321 322 U-Boot can detect if an IDE device is present or not. 323 If not, and this new config option is activated, U-Boot 324 removes the ATA node from the DTS before booting Linux, 325 so the Linux IDE driver does not probe the device and 326 crash. This is needed for buggy hardware (uc101) where 327 no pull down resistor is connected to the signal IDE5V_DD7. 328 329- vxWorks boot parameters: 330 331 bootvx constructs a valid bootline using the following 332 environments variables: bootdev, bootfile, ipaddr, netmask, 333 serverip, gatewayip, hostname, othbootargs. 334 It loads the vxWorks image pointed bootfile. 335 336 Note: If a "bootargs" environment is defined, it will override 337 the defaults discussed just above. 338 339- Cache Configuration for ARM: 340 CFG_SYS_PL310_BASE - Physical base address of PL310 341 controller register space 342 343- Serial Ports: 344 CFG_PL011_CLOCK 345 346 If you have Amba PrimeCell PL011 UARTs, set this variable to 347 the clock speed of the UARTs. 348 349 CFG_PL01x_PORTS 350 351 If you have Amba PrimeCell PL010 or PL011 UARTs on your board, 352 define this to a list of base addresses for each (supported) 353 port. See e.g. include/configs/versatile.h 354 355 CONFIG_SERIAL_HW_FLOW_CONTROL 356 357 Define this variable to enable hw flow control in serial driver. 358 Current user of this option is drivers/serial/nsl16550.c driver 359 360- Removal of commands 361 If no commands are needed to boot, you can disable 362 CONFIG_CMDLINE to remove them. In this case, the command line 363 will not be available, and when U-Boot wants to execute the 364 boot command (on start-up) it will call board_run_command() 365 instead. This can reduce image size significantly for very 366 simple boot procedures. 367 368- Regular expression support: 369 CONFIG_REGEX 370 If this variable is defined, U-Boot is linked against 371 the SLRE (Super Light Regular Expression) library, 372 which adds regex support to some commands, as for 373 example "env grep" and "setexpr". 374 375- Watchdog: 376 CFG_SYS_WATCHDOG_FREQ 377 Some platforms automatically call WATCHDOG_RESET() 378 from the timer interrupt handler every 379 CFG_SYS_WATCHDOG_FREQ interrupts. If not set by the 380 board configuration file, a default of CONFIG_SYS_HZ/2 381 (i.e. 500) is used. Setting CFG_SYS_WATCHDOG_FREQ 382 to 0 disables calling WATCHDOG_RESET() from the timer 383 interrupt. 384 385- GPIO Support: 386 The CFG_SYS_I2C_PCA953X_WIDTH option specifies a list of 387 chip-ngpio pairs that tell the PCA953X driver the number of 388 pins supported by a particular chip. 389 390 Note that if the GPIO device uses I2C, then the I2C interface 391 must also be configured. See I2C Support, below. 392 393- I/O tracing: 394 When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O 395 accesses and can checksum them or write a list of them out 396 to memory. See the 'iotrace' command for details. This is 397 useful for testing device drivers since it can confirm that 398 the driver behaves the same way before and after a code 399 change. Currently this is supported on sandbox and arm. To 400 add support for your architecture, add '#include <iotrace.h>' 401 to the bottom of arch/<arch>/include/asm/io.h and test. 402 403 Example output from the 'iotrace stats' command is below. 404 Note that if the trace buffer is exhausted, the checksum will 405 still continue to operate. 406 407 iotrace is enabled 408 Start: 10000000 (buffer start address) 409 Size: 00010000 (buffer size) 410 Offset: 00000120 (current buffer offset) 411 Output: 10000120 (start + offset) 412 Count: 00000018 (number of trace records) 413 CRC32: 9526fb66 (CRC32 of all trace records) 414 415- Timestamp Support: 416 417 When CONFIG_TIMESTAMP is selected, the timestamp 418 (date and time) of an image is printed by image 419 commands like bootm or iminfo. This option is 420 automatically enabled when you select CONFIG_CMD_DATE . 421 422- Partition Labels (disklabels) Supported: 423 Zero or more of the following: 424 CONFIG_MAC_PARTITION Apple's MacOS partition table. 425 CONFIG_ISO_PARTITION ISO partition table, used on CDROM etc. 426 CONFIG_EFI_PARTITION GPT partition table, common when EFI is the 427 bootloader. Note 2TB partition limit; see 428 disk/part_efi.c 429 CONFIG_SCSI) you must configure support for at 430 least one non-MTD partition type as well. 431 432- NETWORK Support (PCI): 433 CONFIG_E1000_SPI 434 Utility code for direct access to the SPI bus on Intel 8257x. 435 This does not do anything useful unless you set at least one 436 of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC. 437 438 CONFIG_NATSEMI 439 Support for National dp83815 chips. 440 441 CONFIG_NS8382X 442 Support for National dp8382[01] gigabit chips. 443 444- NETWORK Support (other): 445 CONFIG_CALXEDA_XGMAC 446 Support for the Calxeda XGMAC device 447 448 CONFIG_LAN91C96 449 Support for SMSC's LAN91C96 chips. 450 451 CONFIG_LAN91C96_USE_32_BIT 452 Define this to enable 32 bit addressing 453 454 CFG_SYS_DAVINCI_EMAC_PHY_COUNT 455 Define this if you have more then 3 PHYs. 456 457 CONFIG_FTGMAC100 458 Support for Faraday's FTGMAC100 Gigabit SoC Ethernet 459 460 CONFIG_FTGMAC100_EGIGA 461 Define this to use GE link update with gigabit PHY. 462 Define this if FTGMAC100 is connected to gigabit PHY. 463 If your system has 10/100 PHY only, it might not occur 464 wrong behavior. Because PHY usually return timeout or 465 useless data when polling gigabit status and gigabit 466 control registers. This behavior won't affect the 467 correctnessof 10/100 link speed update. 468 469 CONFIG_SH_ETHER 470 Support for Renesas on-chip Ethernet controller 471 472 CFG_SH_ETHER_USE_PORT 473 Define the number of ports to be used 474 475 CFG_SH_ETHER_PHY_ADDR 476 Define the ETH PHY's address 477 478 CFG_SH_ETHER_CACHE_WRITEBACK 479 If this option is set, the driver enables cache flush. 480 481- TPM Support: 482 CONFIG_TPM 483 Support TPM devices. 484 485 CONFIG_TPM_TIS_INFINEON 486 Support for Infineon i2c bus TPM devices. Only one device 487 per system is supported at this time. 488 489 CONFIG_TPM_TIS_I2C_BURST_LIMITATION 490 Define the burst count bytes upper limit 491 492 CONFIG_TPM_ST33ZP24 493 Support for STMicroelectronics TPM devices. Requires DM_TPM support. 494 495 CONFIG_TPM_ST33ZP24_I2C 496 Support for STMicroelectronics ST33ZP24 I2C devices. 497 Requires TPM_ST33ZP24 and I2C. 498 499 CONFIG_TPM_ST33ZP24_SPI 500 Support for STMicroelectronics ST33ZP24 SPI devices. 501 Requires TPM_ST33ZP24 and SPI. 502 503 CONFIG_TPM_ATMEL_TWI 504 Support for Atmel TWI TPM device. Requires I2C support. 505 506 CONFIG_TPM_TIS_LPC 507 Support for generic parallel port TPM devices. Only one device 508 per system is supported at this time. 509 510 CONFIG_TPM 511 Define this to enable the TPM support library which provides 512 functional interfaces to some TPM commands. 513 Requires support for a TPM device. 514 515 CONFIG_TPM_AUTH_SESSIONS 516 Define this to enable authorized functions in the TPM library. 517 Requires CONFIG_TPM and CONFIG_SHA1. 518 519- USB Support: 520 At the moment only the UHCI host controller is 521 supported (PIP405, MIP405); define 522 CONFIG_USB_UHCI to enable it. 523 define CONFIG_USB_KEYBOARD to enable the USB Keyboard 524 and define CONFIG_USB_STORAGE to enable the USB 525 storage devices. 526 Note: 527 Supported are USB Keyboards and USB Floppy drives 528 (TEAC FD-05PUB). 529 530 CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2 531 HW module registers. 532 533- USB Device: 534 Define the below if you wish to use the USB console. 535 Once firmware is rebuilt from a serial console issue the 536 command "setenv stdin usbtty; setenv stdout usbtty" and 537 attach your USB cable. The Unix command "dmesg" should print 538 it has found a new device. The environment variable usbtty 539 can be set to gserial or cdc_acm to enable your device to 540 appear to a USB host as a Linux gserial device or a 541 Common Device Class Abstract Control Model serial device. 542 If you select usbtty = gserial you should be able to enumerate 543 a Linux host by 544 # modprobe usbserial vendor=0xVendorID product=0xProductID 545 else if using cdc_acm, simply setting the environment 546 variable usbtty to be cdc_acm should suffice. The following 547 might be defined in YourBoardName.h 548 549 If you have a USB-IF assigned VendorID then you may wish to 550 define your own vendor specific values either in BoardName.h 551 or directly in usbd_vendor_info.h. If you don't define 552 CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME, 553 CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot 554 should pretend to be a Linux device to it's target host. 555 556 CONFIG_USBD_MANUFACTURER 557 Define this string as the name of your company for 558 - CONFIG_USBD_MANUFACTURER "my company" 559 560 CONFIG_USBD_PRODUCT_NAME 561 Define this string as the name of your product 562 - CONFIG_USBD_PRODUCT_NAME "acme usb device" 563 564 CONFIG_USBD_VENDORID 565 Define this as your assigned Vendor ID from the USB 566 Implementors Forum. This *must* be a genuine Vendor ID 567 to avoid polluting the USB namespace. 568 - CONFIG_USBD_VENDORID 0xFFFF 569 570 CONFIG_USBD_PRODUCTID 571 Define this as the unique Product ID 572 for your device 573 - CONFIG_USBD_PRODUCTID 0xFFFF 574 575- ULPI Layer Support: 576 The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via 577 the generic ULPI layer. The generic layer accesses the ULPI PHY 578 via the platform viewport, so you need both the genric layer and 579 the viewport enabled. Currently only Chipidea/ARC based 580 viewport is supported. 581 To enable the ULPI layer support, define CONFIG_USB_ULPI and 582 CONFIG_USB_ULPI_VIEWPORT in your board configuration file. 583 If your ULPI phy needs a different reference clock than the 584 standard 24 MHz then you have to define CFG_ULPI_REF_CLK to 585 the appropriate value in Hz. 586 587- MMC Support: 588 CONFIG_SH_MMCIF 589 Support for Renesas on-chip MMCIF controller 590 591 CONFIG_SH_MMCIF_ADDR 592 Define the base address of MMCIF registers 593 594 CONFIG_SH_MMCIF_CLK 595 Define the clock frequency for MMCIF 596 597- USB Device Firmware Update (DFU) class support: 598 CONFIG_DFU_OVER_USB 599 This enables the USB portion of the DFU USB class 600 601 CONFIG_DFU_NAND 602 This enables support for exposing NAND devices via DFU. 603 604 CONFIG_DFU_RAM 605 This enables support for exposing RAM via DFU. 606 Note: DFU spec refer to non-volatile memory usage, but 607 allow usages beyond the scope of spec - here RAM usage, 608 one that would help mostly the developer. 609 610 CONFIG_SYS_DFU_DATA_BUF_SIZE 611 Dfu transfer uses a buffer before writing data to the 612 raw storage device. Make the size (in bytes) of this buffer 613 configurable. The size of this buffer is also configurable 614 through the "dfu_bufsiz" environment variable. 615 616 CONFIG_SYS_DFU_MAX_FILE_SIZE 617 When updating files rather than the raw storage device, 618 we use a static buffer to copy the file into and then write 619 the buffer once we've been given the whole file. Define 620 this to the maximum filesize (in bytes) for the buffer. 621 Default is 4 MiB if undefined. 622 623 DFU_DEFAULT_POLL_TIMEOUT 624 Poll timeout [ms], is the timeout a device can send to the 625 host. The host must wait for this timeout before sending 626 a subsequent DFU_GET_STATUS request to the device. 627 628 DFU_MANIFEST_POLL_TIMEOUT 629 Poll timeout [ms], which the device sends to the host when 630 entering dfuMANIFEST state. Host waits this timeout, before 631 sending again an USB request to the device. 632 633- Keyboard Support: 634 See Kconfig help for available keyboard drivers. 635 636- MII/PHY support: 637 CONFIG_PHY_CLOCK_FREQ (ppc4xx) 638 639 The clock frequency of the MII bus 640 641 CONFIG_PHY_CMD_DELAY (ppc4xx) 642 643 Some PHY like Intel LXT971A need extra delay after 644 command issued before MII status register can be read 645 646- BOOTP Recovery Mode: 647 CONFIG_BOOTP_RANDOM_DELAY 648 649 If you have many targets in a network that try to 650 boot using BOOTP, you may want to avoid that all 651 systems send out BOOTP requests at precisely the same 652 moment (which would happen for instance at recovery 653 from a power failure, when all systems will try to 654 boot, thus flooding the BOOTP server. Defining 655 CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be 656 inserted before sending out BOOTP requests. The 657 following delays are inserted then: 658 659 1st BOOTP request: delay 0 ... 1 sec 660 2nd BOOTP request: delay 0 ... 2 sec 661 3rd BOOTP request: delay 0 ... 4 sec 662 4th and following 663 BOOTP requests: delay 0 ... 8 sec 664 665 CFG_BOOTP_ID_CACHE_SIZE 666 667 BOOTP packets are uniquely identified using a 32-bit ID. The 668 server will copy the ID from client requests to responses and 669 U-Boot will use this to determine if it is the destination of 670 an incoming response. Some servers will check that addresses 671 aren't in use before handing them out (usually using an ARP 672 ping) and therefore take up to a few hundred milliseconds to 673 respond. Network congestion may also influence the time it 674 takes for a response to make it back to the client. If that 675 time is too long, U-Boot will retransmit requests. In order 676 to allow earlier responses to still be accepted after these 677 retransmissions, U-Boot's BOOTP client keeps a small cache of 678 IDs. The CFG_BOOTP_ID_CACHE_SIZE controls the size of this 679 cache. The default is to keep IDs for up to four outstanding 680 requests. Increasing this will allow U-Boot to accept offers 681 from a BOOTP client in networks with unusually high latency. 682 683- DHCP Advanced Options: 684 685 - Link-local IP address negotiation: 686 Negotiate with other link-local clients on the local network 687 for an address that doesn't require explicit configuration. 688 This is especially useful if a DHCP server cannot be guaranteed 689 to exist in all environments that the device must operate. 690 691 See doc/README.link-local for more information. 692 693 - MAC address from environment variables 694 695 FDT_SEQ_MACADDR_FROM_ENV 696 697 Fix-up device tree with MAC addresses fetched sequentially from 698 environment variables. This config work on assumption that 699 non-usable ethernet node of device-tree are either not present 700 or their status has been marked as "disabled". 701 702 - CDP Options: 703 CONFIG_CDP_DEVICE_ID 704 705 The device id used in CDP trigger frames. 706 707 CONFIG_CDP_DEVICE_ID_PREFIX 708 709 A two character string which is prefixed to the MAC address 710 of the device. 711 712 CONFIG_CDP_PORT_ID 713 714 A printf format string which contains the ascii name of 715 the port. Normally is set to "eth%d" which sets 716 eth0 for the first Ethernet, eth1 for the second etc. 717 718 CONFIG_CDP_CAPABILITIES 719 720 A 32bit integer which indicates the device capabilities; 721 0x00000010 for a normal host which does not forwards. 722 723 CONFIG_CDP_VERSION 724 725 An ascii string containing the version of the software. 726 727 CONFIG_CDP_PLATFORM 728 729 An ascii string containing the name of the platform. 730 731 CONFIG_CDP_TRIGGER 732 733 A 32bit integer sent on the trigger. 734 735 CONFIG_CDP_POWER_CONSUMPTION 736 737 A 16bit integer containing the power consumption of the 738 device in .1 of milliwatts. 739 740 CONFIG_CDP_APPLIANCE_VLAN_TYPE 741 742 A byte containing the id of the VLAN. 743 744- Status LED: CONFIG_LED_STATUS 745 746 Several configurations allow to display the current 747 status using a LED. For instance, the LED will blink 748 fast while running U-Boot code, stop blinking as 749 soon as a reply to a BOOTP request was received, and 750 start blinking slow once the Linux kernel is running 751 (supported by a status LED driver in the Linux 752 kernel). Defining CONFIG_LED_STATUS enables this 753 feature in U-Boot. 754 755 Additional options: 756 757 CONFIG_LED_STATUS_GPIO 758 The status LED can be connected to a GPIO pin. 759 In such cases, the gpio_led driver can be used as a 760 status LED backend implementation. Define CONFIG_LED_STATUS_GPIO 761 to include the gpio_led driver in the U-Boot binary. 762 763 CFG_GPIO_LED_INVERTED_TABLE 764 Some GPIO connected LEDs may have inverted polarity in which 765 case the GPIO high value corresponds to LED off state and 766 GPIO low value corresponds to LED on state. 767 In such cases CFG_GPIO_LED_INVERTED_TABLE may be defined 768 with a list of GPIO LEDs that have inverted polarity. 769 770- I2C Support: 771 CFG_SYS_NUM_I2C_BUSES 772 Hold the number of i2c buses you want to use. 773 774 CFG_SYS_I2C_DIRECT_BUS 775 define this, if you don't use i2c muxes on your hardware. 776 if CFG_SYS_I2C_MAX_HOPS is not defined or == 0 you can 777 omit this define. 778 779 CFG_SYS_I2C_MAX_HOPS 780 define how many muxes are maximal consecutively connected 781 on one i2c bus. If you not use i2c muxes, omit this 782 define. 783 784 CFG_SYS_I2C_BUSES 785 hold a list of buses you want to use, only used if 786 CFG_SYS_I2C_DIRECT_BUS is not defined, for example 787 a board with CFG_SYS_I2C_MAX_HOPS = 1 and 788 CFG_SYS_NUM_I2C_BUSES = 9: 789 790 CFG_SYS_I2C_BUSES {{0, {I2C_NULL_HOP}}, \ 791 {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \ 792 {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \ 793 {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \ 794 {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \ 795 {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \ 796 {1, {I2C_NULL_HOP}}, \ 797 {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \ 798 {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \ 799 } 800 801 which defines 802 bus 0 on adapter 0 without a mux 803 bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1 804 bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2 805 bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3 806 bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4 807 bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5 808 bus 6 on adapter 1 without a mux 809 bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1 810 bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2 811 812 If you do not have i2c muxes on your board, omit this define. 813 814- Legacy I2C Support: 815 If you use the software i2c interface (CONFIG_SYS_I2C_SOFT) 816 then the following macros need to be defined (examples are 817 from include/configs/lwmon.h): 818 819 I2C_INIT 820 821 (Optional). Any commands necessary to enable the I2C 822 controller or configure ports. 823 824 eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL) 825 826 I2C_ACTIVE 827 828 The code necessary to make the I2C data line active 829 (driven). If the data line is open collector, this 830 define can be null. 831 832 eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA) 833 834 I2C_TRISTATE 835 836 The code necessary to make the I2C data line tri-stated 837 (inactive). If the data line is open collector, this 838 define can be null. 839 840 eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA) 841 842 I2C_READ 843 844 Code that returns true if the I2C data line is high, 845 false if it is low. 846 847 eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0) 848 849 I2C_SDA(bit) 850 851 If <bit> is true, sets the I2C data line high. If it 852 is false, it clears it (low). 853 854 eg: #define I2C_SDA(bit) \ 855 if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \ 856 else immr->im_cpm.cp_pbdat &= ~PB_SDA 857 858 I2C_SCL(bit) 859 860 If <bit> is true, sets the I2C clock line high. If it 861 is false, it clears it (low). 862 863 eg: #define I2C_SCL(bit) \ 864 if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \ 865 else immr->im_cpm.cp_pbdat &= ~PB_SCL 866 867 I2C_DELAY 868 869 This delay is invoked four times per clock cycle so this 870 controls the rate of data transfer. The data rate thus 871 is 1 / (I2C_DELAY * 4). Often defined to be something 872 like: 873 874 #define I2C_DELAY udelay(2) 875 876 CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA 877 878 If your arch supports the generic GPIO framework (asm/gpio.h), 879 then you may alternatively define the two GPIOs that are to be 880 used as SCL / SDA. Any of the previous I2C_xxx macros will 881 have GPIO-based defaults assigned to them as appropriate. 882 883 You should define these to the GPIO value as given directly to 884 the generic GPIO functions. 885 886 CFG_I2C_MULTI_BUS 887 888 This option allows the use of multiple I2C buses, each of which 889 must have a controller. At any point in time, only one bus is 890 active. To switch to a different bus, use the 'i2c dev' command. 891 Note that bus numbering is zero-based. 892 893 CFG_SYS_I2C_NOPROBES 894 895 This option specifies a list of I2C devices that will be skipped 896 when the 'i2c probe' command is issued. 897 898 e.g. 899 #define CFG_SYS_I2C_NOPROBES {0x50,0x68} 900 901 will skip addresses 0x50 and 0x68 on a board with one I2C bus 902 903 CFG_SYS_RTC_BUS_NUM 904 905 If defined, then this indicates the I2C bus number for the RTC. 906 If not defined, then U-Boot assumes that RTC is on I2C bus 0. 907 908 CONFIG_SOFT_I2C_READ_REPEATED_START 909 910 defining this will force the i2c_read() function in 911 the soft_i2c driver to perform an I2C repeated start 912 between writing the address pointer and reading the 913 data. If this define is omitted the default behaviour 914 of doing a stop-start sequence will be used. Most I2C 915 devices can use either method, but some require one or 916 the other. 917 918- SPI Support: CONFIG_SPI 919 920 Enables SPI driver (so far only tested with 921 SPI EEPROM, also an instance works with Crystal A/D and 922 D/As on the SACSng board) 923 924 CFG_SYS_SPI_MXC_WAIT 925 Timeout for waiting until spi transfer completed. 926 default: (CONFIG_SYS_HZ/100) /* 10 ms */ 927 928- FPGA Support: CONFIG_FPGA 929 930 Enables FPGA subsystem. 931 932 CONFIG_FPGA_<vendor> 933 934 Enables support for specific chip vendors. 935 (ALTERA, XILINX) 936 937 CONFIG_FPGA_<family> 938 939 Enables support for FPGA family. 940 (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX) 941 942 CONFIG_SYS_FPGA_CHECK_BUSY 943 944 Enable checks on FPGA configuration interface busy 945 status by the configuration function. This option 946 will require a board or device specific function to 947 be written. 948 949 CFG_FPGA_DELAY 950 951 If defined, a function that provides delays in the FPGA 952 configuration driver. 953 954 CFG_SYS_FPGA_CHECK_ERROR 955 956 Check for configuration errors during FPGA bitfile 957 loading. For example, abort during Virtex II 958 configuration if the INIT_B line goes low (which 959 indicated a CRC error). 960 961 CFG_SYS_FPGA_WAIT_INIT 962 963 Maximum time to wait for the INIT_B line to de-assert 964 after PROB_B has been de-asserted during a Virtex II 965 FPGA configuration sequence. The default time is 500 966 ms. 967 968 CFG_SYS_FPGA_WAIT_BUSY 969 970 Maximum time to wait for BUSY to de-assert during 971 Virtex II FPGA configuration. The default is 5 ms. 972 973 CFG_SYS_FPGA_WAIT_CONFIG 974 975 Time to wait after FPGA configuration. The default is 976 200 ms. 977 978- Vendor Parameter Protection: 979 980 U-Boot considers the values of the environment 981 variables "serial#" (Board Serial Number) and 982 "ethaddr" (Ethernet Address) to be parameters that 983 are set once by the board vendor / manufacturer, and 984 protects these variables from casual modification by 985 the user. Once set, these variables are read-only, 986 and write or delete attempts are rejected. You can 987 change this behaviour: 988 989 If CONFIG_ENV_OVERWRITE is #defined in your config 990 file, the write protection for vendor parameters is 991 completely disabled. Anybody can change or delete 992 these parameters. 993 994 The same can be accomplished in a more flexible way 995 for any variable by configuring the type of access 996 to allow for those variables in the ".flags" variable 997 or define CFG_ENV_FLAGS_LIST_STATIC. 998 999- Protected RAM: 1000 CFG_PRAM 1001 1002 Define this variable to enable the reservation of 1003 "protected RAM", i. e. RAM which is not overwritten 1004 by U-Boot. Define CFG_PRAM to hold the number of 1005 kB you want to reserve for pRAM. You can overwrite 1006 this default value by defining an environment 1007 variable "pram" to the number of kB you want to 1008 reserve. Note that the board info structure will 1009 still show the full amount of RAM. If pRAM is 1010 reserved, a new environment variable "mem" will 1011 automatically be defined to hold the amount of 1012 remaining RAM in a form that can be passed as boot 1013 argument to Linux, for instance like that: 1014 1015 setenv bootargs ... mem=\${mem} 1016 saveenv 1017 1018 This way you can tell Linux not to use this memory, 1019 either, which results in a memory region that will 1020 not be affected by reboots. 1021 1022 *WARNING* If your board configuration uses automatic 1023 detection of the RAM size, you must make sure that 1024 this memory test is non-destructive. So far, the 1025 following board configurations are known to be 1026 "pRAM-clean": 1027 1028 IVMS8, IVML24, SPD8xx, 1029 HERMES, IP860, RPXlite, LWMON, 1030 FLAGADM 1031 1032- Error Recovery: 1033 Note: 1034 1035 In the current implementation, the local variables 1036 space and global environment variables space are 1037 separated. Local variables are those you define by 1038 simply typing `name=value'. To access a local 1039 variable later on, you have write `$name' or 1040 `${name}'; to execute the contents of a variable 1041 directly type `$name' at the command prompt. 1042 1043 Global environment variables are those you use 1044 setenv/printenv to work with. To run a command stored 1045 in such a variable, you need to use the run command, 1046 and you must not use the '$' sign to access them. 1047 1048 To store commands and special characters in a 1049 variable, please use double quotation marks 1050 surrounding the whole text of the variable, instead 1051 of the backslashes before semicolons and special 1052 symbols. 1053 1054- Default Environment: 1055 CFG_EXTRA_ENV_SETTINGS 1056 1057 Define this to contain any number of null terminated 1058 strings (variable = value pairs) that will be part of 1059 the default environment compiled into the boot image. 1060 1061 For example, place something like this in your 1062 board's config file: 1063 1064 #define CFG_EXTRA_ENV_SETTINGS \ 1065 "myvar1=value1\0" \ 1066 "myvar2=value2\0" 1067 1068 Warning: This method is based on knowledge about the 1069 internal format how the environment is stored by the 1070 U-Boot code. This is NOT an official, exported 1071 interface! Although it is unlikely that this format 1072 will change soon, there is no guarantee either. 1073 You better know what you are doing here. 1074 1075 Note: overly (ab)use of the default environment is 1076 discouraged. Make sure to check other ways to preset 1077 the environment like the "source" command or the 1078 boot command first. 1079 1080 CONFIG_DELAY_ENVIRONMENT 1081 1082 Normally the environment is loaded when the board is 1083 initialised so that it is available to U-Boot. This inhibits 1084 that so that the environment is not available until 1085 explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL 1086 this is instead controlled by the value of 1087 /config/load-environment. 1088 1089- Automatic software updates via TFTP server 1090 CONFIG_UPDATE_TFTP 1091 CONFIG_UPDATE_TFTP_CNT_MAX 1092 CONFIG_UPDATE_TFTP_MSEC_MAX 1093 1094 These options enable and control the auto-update feature; 1095 for a more detailed description refer to doc/README.update. 1096 1097- MTD Support (mtdparts command, UBI support) 1098 CONFIG_MTD_UBI_WL_THRESHOLD 1099 This parameter defines the maximum difference between the highest 1100 erase counter value and the lowest erase counter value of eraseblocks 1101 of UBI devices. When this threshold is exceeded, UBI starts performing 1102 wear leveling by means of moving data from eraseblock with low erase 1103 counter to eraseblocks with high erase counter. 1104 1105 The default value should be OK for SLC NAND flashes, NOR flashes and 1106 other flashes which have eraseblock life-cycle 100000 or more. 1107 However, in case of MLC NAND flashes which typically have eraseblock 1108 life-cycle less than 10000, the threshold should be lessened (e.g., 1109 to 128 or 256, although it does not have to be power of 2). 1110 1111 default: 4096 1112 1113 CONFIG_MTD_UBI_BEB_LIMIT 1114 This option specifies the maximum bad physical eraseblocks UBI 1115 expects on the MTD device (per 1024 eraseblocks). If the 1116 underlying flash does not admit of bad eraseblocks (e.g. NOR 1117 flash), this value is ignored. 1118 1119 NAND datasheets often specify the minimum and maximum NVM 1120 (Number of Valid Blocks) for the flashes' endurance lifetime. 1121 The maximum expected bad eraseblocks per 1024 eraseblocks 1122 then can be calculated as "1024 * (1 - MinNVB / MaxNVB)", 1123 which gives 20 for most NANDs (MaxNVB is basically the total 1124 count of eraseblocks on the chip). 1125 1126 To put it differently, if this value is 20, UBI will try to 1127 reserve about 1.9% of physical eraseblocks for bad blocks 1128 handling. And that will be 1.9% of eraseblocks on the entire 1129 NAND chip, not just the MTD partition UBI attaches. This means 1130 that if you have, say, a NAND flash chip admits maximum 40 bad 1131 eraseblocks, and it is split on two MTD partitions of the same 1132 size, UBI will reserve 40 eraseblocks when attaching a 1133 partition. 1134 1135 default: 20 1136 1137 CONFIG_MTD_UBI_FASTMAP 1138 Fastmap is a mechanism which allows attaching an UBI device 1139 in nearly constant time. Instead of scanning the whole MTD device it 1140 only has to locate a checkpoint (called fastmap) on the device. 1141 The on-flash fastmap contains all information needed to attach 1142 the device. Using fastmap makes only sense on large devices where 1143 attaching by scanning takes long. UBI will not automatically install 1144 a fastmap on old images, but you can set the UBI parameter 1145 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note 1146 that fastmap-enabled images are still usable with UBI implementations 1147 without fastmap support. On typical flash devices the whole fastmap 1148 fits into one PEB. UBI will reserve PEBs to hold two fastmaps. 1149 1150 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT 1151 Set this parameter to enable fastmap automatically on images 1152 without a fastmap. 1153 default: 0 1154 1155 CONFIG_MTD_UBI_FM_DEBUG 1156 Enable UBI fastmap debug 1157 default: 0 1158 1159- SPL framework 1160 CONFIG_SPL 1161 Enable building of SPL globally. 1162 1163 CONFIG_SPL_PANIC_ON_RAW_IMAGE 1164 When defined, SPL will panic() if the image it has 1165 loaded does not have a signature. 1166 Defining this is useful when code which loads images 1167 in SPL cannot guarantee that absolutely all read errors 1168 will be caught. 1169 An example is the LPC32XX MLC NAND driver, which will 1170 consider that a completely unreadable NAND block is bad, 1171 and thus should be skipped silently. 1172 1173 CONFIG_SPL_DISPLAY_PRINT 1174 For ARM, enable an optional function to print more information 1175 about the running system. 1176 1177 CONFIG_SPL_MPC83XX_WAIT_FOR_NAND 1178 Set this for NAND SPL on PPC mpc83xx targets, so that 1179 start.S waits for the rest of the SPL to load before 1180 continuing (the hardware starts execution after just 1181 loading the first page rather than the full 4K). 1182 1183 CONFIG_SPL_UBI 1184 Support for a lightweight UBI (fastmap) scanner and 1185 loader 1186 1187 CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_SIZE, 1188 CONFIG_SYS_NAND_OOBSIZE, CONFIG_SYS_NAND_BLOCK_SIZE, 1189 CONFIG_SYS_NAND_BAD_BLOCK_POS, CFG_SYS_NAND_ECCPOS, 1190 CFG_SYS_NAND_ECCSIZE, CFG_SYS_NAND_ECCBYTES 1191 Defines the size and behavior of the NAND that SPL uses 1192 to read U-Boot 1193 1194 CFG_SYS_NAND_U_BOOT_DST 1195 Location in memory to load U-Boot to 1196 1197 CFG_SYS_NAND_U_BOOT_SIZE 1198 Size of image to load 1199 1200 CFG_SYS_NAND_U_BOOT_START 1201 Entry point in loaded image to jump to 1202 1203 CONFIG_SPL_RAM_DEVICE 1204 Support for running image already present in ram, in SPL binary 1205 1206 CONFIG_SPL_FIT_PRINT 1207 Printing information about a FIT image adds quite a bit of 1208 code to SPL. So this is normally disabled in SPL. Use this 1209 option to re-enable it. This will affect the output of the 1210 bootm command when booting a FIT image. 1211 1212- Interrupt support (PPC): 1213 1214 There are common interrupt_init() and timer_interrupt() 1215 for all PPC archs. interrupt_init() calls interrupt_init_cpu() 1216 for CPU specific initialization. interrupt_init_cpu() 1217 should set decrementer_count to appropriate value. If 1218 CPU resets decrementer automatically after interrupt 1219 (ppc4xx) it should set decrementer_count to zero. 1220 timer_interrupt() calls timer_interrupt_cpu() for CPU 1221 specific handling. If board has watchdog / status_led 1222 / other_activity_monitor it works automatically from 1223 general timer_interrupt(). 1224 1225 1226Board initialization settings: 1227------------------------------ 1228 1229During Initialization u-boot calls a number of board specific functions 1230to allow the preparation of board specific prerequisites, e.g. pin setup 1231before drivers are initialized. To enable these callbacks the 1232following configuration macros have to be defined. Currently this is 1233architecture specific, so please check arch/your_architecture/lib/board.c 1234typically in board_init_f() and board_init_r(). 1235 1236- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f() 1237- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r() 1238- CONFIG_BOARD_LATE_INIT: Call board_late_init() 1239 1240Configuration Settings: 1241----------------------- 1242 1243- CONFIG_SYS_LONGHELP: Defined when you want long help messages included; 1244 undefine this when you're short of memory. 1245 1246- CFG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default 1247 width of the commands listed in the 'help' command output. 1248 1249- CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to 1250 prompt for user input. 1251 1252- CFG_SYS_BAUDRATE_TABLE: 1253 List of legal baudrate settings for this board. 1254 1255- CFG_SYS_MEM_RESERVE_SECURE 1256 Only implemented for ARMv8 for now. 1257 If defined, the size of CFG_SYS_MEM_RESERVE_SECURE memory 1258 is substracted from total RAM and won't be reported to OS. 1259 This memory can be used as secure memory. A variable 1260 gd->arch.secure_ram is used to track the location. In systems 1261 the RAM base is not zero, or RAM is divided into banks, 1262 this variable needs to be recalcuated to get the address. 1263 1264- CFG_SYS_SDRAM_BASE: 1265 Physical start address of SDRAM. _Must_ be 0 here. 1266 1267- CFG_SYS_FLASH_BASE: 1268 Physical start address of Flash memory. 1269 1270- CONFIG_SYS_MALLOC_LEN: 1271 Size of DRAM reserved for malloc() use. 1272 1273- CFG_SYS_BOOTMAPSZ: 1274 Maximum size of memory mapped by the startup code of 1275 the Linux kernel; all data that must be processed by 1276 the Linux kernel (bd_info, boot arguments, FDT blob if 1277 used) must be put below this limit, unless "bootm_low" 1278 environment variable is defined and non-zero. In such case 1279 all data for the Linux kernel must be between "bootm_low" 1280 and "bootm_low" + CFG_SYS_BOOTMAPSZ. The environment 1281 variable "bootm_mapsize" will override the value of 1282 CFG_SYS_BOOTMAPSZ. If CFG_SYS_BOOTMAPSZ is undefined, 1283 then the value in "bootm_size" will be used instead. 1284 1285- CONFIG_SYS_BOOT_GET_CMDLINE: 1286 Enables allocating and saving kernel cmdline in space between 1287 "bootm_low" and "bootm_low" + BOOTMAPSZ. 1288 1289- CONFIG_SYS_BOOT_GET_KBD: 1290 Enables allocating and saving a kernel copy of the bd_info in 1291 space between "bootm_low" and "bootm_low" + BOOTMAPSZ. 1292 1293- CONFIG_SYS_FLASH_PROTECTION 1294 If defined, hardware flash sectors protection is used 1295 instead of U-Boot software protection. 1296 1297- CONFIG_SYS_FLASH_CFI: 1298 Define if the flash driver uses extra elements in the 1299 common flash structure for storing flash geometry. 1300 1301- CONFIG_FLASH_CFI_DRIVER 1302 This option also enables the building of the cfi_flash driver 1303 in the drivers directory 1304 1305- CONFIG_FLASH_CFI_MTD 1306 This option enables the building of the cfi_mtd driver 1307 in the drivers directory. The driver exports CFI flash 1308 to the MTD layer. 1309 1310- CONFIG_SYS_FLASH_USE_BUFFER_WRITE 1311 Use buffered writes to flash. 1312 1313- CONFIG_ENV_FLAGS_LIST_DEFAULT 1314- CFG_ENV_FLAGS_LIST_STATIC 1315 Enable validation of the values given to environment variables when 1316 calling env set. Variables can be restricted to only decimal, 1317 hexadecimal, or boolean. If CONFIG_CMD_NET is also defined, 1318 the variables can also be restricted to IP address or MAC address. 1319 1320 The format of the list is: 1321 type_attribute = [s|d|x|b|i|m] 1322 access_attribute = [a|r|o|c] 1323 attributes = type_attribute[access_attribute] 1324 entry = variable_name[:attributes] 1325 list = entry[,list] 1326 1327 The type attributes are: 1328 s - String (default) 1329 d - Decimal 1330 x - Hexadecimal 1331 b - Boolean ([1yYtT|0nNfF]) 1332 i - IP address 1333 m - MAC address 1334 1335 The access attributes are: 1336 a - Any (default) 1337 r - Read-only 1338 o - Write-once 1339 c - Change-default 1340 1341 - CONFIG_ENV_FLAGS_LIST_DEFAULT 1342 Define this to a list (string) to define the ".flags" 1343 environment variable in the default or embedded environment. 1344 1345 - CFG_ENV_FLAGS_LIST_STATIC 1346 Define this to a list (string) to define validation that 1347 should be done if an entry is not found in the ".flags" 1348 environment variable. To override a setting in the static 1349 list, simply add an entry for the same variable name to the 1350 ".flags" variable. 1351 1352 If CONFIG_REGEX is defined, the variable_name above is evaluated as a 1353 regular expression. This allows multiple variables to define the same 1354 flags without explicitly listing them for each variable. 1355 1356The following definitions that deal with the placement and management 1357of environment data (variable area); in general, we support the 1358following configurations: 1359 1360BE CAREFUL! The first access to the environment happens quite early 1361in U-Boot initialization (when we try to get the setting of for the 1362console baudrate). You *MUST* have mapped your NVRAM area then, or 1363U-Boot will hang. 1364 1365Please note that even with NVRAM we still use a copy of the 1366environment in RAM: we could work on NVRAM directly, but we want to 1367keep settings there always unmodified except somebody uses "saveenv" 1368to save the current settings. 1369 1370BE CAREFUL! For some special cases, the local device can not use 1371"saveenv" command. For example, the local device will get the 1372environment stored in a remote NOR flash by SRIO or PCIE link, 1373but it can not erase, write this NOR flash by SRIO or PCIE interface. 1374 1375- CONFIG_NAND_ENV_DST 1376 1377 Defines address in RAM to which the nand_spl code should copy the 1378 environment. If redundant environment is used, it will be copied to 1379 CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE. 1380 1381Please note that the environment is read-only until the monitor 1382has been relocated to RAM and a RAM copy of the environment has been 1383created; also, when using EEPROM you will have to use env_get_f() 1384until then to read environment variables. 1385 1386The environment is protected by a CRC32 checksum. Before the monitor 1387is relocated into RAM, as a result of a bad CRC you will be working 1388with the compiled-in default environment - *silently*!!! [This is 1389necessary, because the first environment variable we need is the 1390"baudrate" setting for the console - if we have a bad CRC, we don't 1391have any device yet where we could complain.] 1392 1393Note: once the monitor has been relocated, then it will complain if 1394the default environment is used; a new CRC is computed as soon as you 1395use the "saveenv" command to store a valid environment. 1396 1397- CONFIG_SYS_FAULT_MII_ADDR: 1398 MII address of the PHY to check for the Ethernet link state. 1399 1400- CONFIG_DISPLAY_BOARDINFO 1401 Display information about the board that U-Boot is running on 1402 when U-Boot starts up. The board function checkboard() is called 1403 to do this. 1404 1405- CONFIG_DISPLAY_BOARDINFO_LATE 1406 Similar to the previous option, but display this information 1407 later, once stdio is running and output goes to the LCD, if 1408 present. 1409 1410Low Level (hardware related) configuration options: 1411--------------------------------------------------- 1412 1413- CONFIG_SYS_CACHELINE_SIZE: 1414 Cache Line Size of the CPU. 1415 1416- CONFIG_SYS_CCSRBAR_DEFAULT: 1417 Default (power-on reset) physical address of CCSR on Freescale 1418 PowerPC SOCs. 1419 1420- CFG_SYS_CCSRBAR: 1421 Virtual address of CCSR. On a 32-bit build, this is typically 1422 the same value as CONFIG_SYS_CCSRBAR_DEFAULT. 1423 1424- CFG_SYS_CCSRBAR_PHYS: 1425 Physical address of CCSR. CCSR can be relocated to a new 1426 physical address, if desired. In this case, this macro should 1427 be set to that address. Otherwise, it should be set to the 1428 same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR 1429 is typically relocated on 36-bit builds. It is recommended 1430 that this macro be defined via the _HIGH and _LOW macros: 1431 1432 #define CFG_SYS_CCSRBAR_PHYS ((CFG_SYS_CCSRBAR_PHYS_HIGH 1433 * 1ull) << 32 | CFG_SYS_CCSRBAR_PHYS_LOW) 1434 1435- CFG_SYS_CCSRBAR_PHYS_HIGH: 1436 Bits 33-36 of CFG_SYS_CCSRBAR_PHYS. This value is typically 1437 either 0 (32-bit build) or 0xF (36-bit build). This macro is 1438 used in assembly code, so it must not contain typecasts or 1439 integer size suffixes (e.g. "ULL"). 1440 1441- CFG_SYS_CCSRBAR_PHYS_LOW: 1442 Lower 32-bits of CFG_SYS_CCSRBAR_PHYS. This macro is 1443 used in assembly code, so it must not contain typecasts or 1444 integer size suffixes (e.g. "ULL"). 1445 1446- CONFIG_SYS_IMMR: Physical address of the Internal Memory. 1447 DO NOT CHANGE unless you know exactly what you're 1448 doing! (11-4) [MPC8xx systems only] 1449 1450- CFG_SYS_INIT_RAM_ADDR: 1451 1452 Start address of memory area that can be used for 1453 initial data and stack; please note that this must be 1454 writable memory that is working WITHOUT special 1455 initialization, i. e. you CANNOT use normal RAM which 1456 will become available only after programming the 1457 memory controller and running certain initialization 1458 sequences. 1459 1460 U-Boot uses the following memory types: 1461 - MPC8xx: IMMR (internal memory of the CPU) 1462 1463- CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27) 1464 1465- CONFIG_SYS_OR_TIMING_SDRAM: 1466 SDRAM timing 1467 1468- CONFIG_SYS_SRIOn_MEM_VIRT: 1469 Virtual Address of SRIO port 'n' memory region 1470 1471- CONFIG_SYS_SRIOn_MEM_PHYxS: 1472 Physical Address of SRIO port 'n' memory region 1473 1474- CONFIG_SYS_SRIOn_MEM_SIZE: 1475 Size of SRIO port 'n' memory region 1476 1477- CONFIG_SYS_NAND_BUSWIDTH_16BIT 1478 Defined to tell the NAND controller that the NAND chip is using 1479 a 16 bit bus. 1480 Not all NAND drivers use this symbol. 1481 Example of drivers that use it: 1482 - drivers/mtd/nand/raw/ndfc.c 1483 - drivers/mtd/nand/raw/mxc_nand.c 1484 1485- CONFIG_SYS_NDFC_EBC0_CFG 1486 Sets the EBC0_CFG register for the NDFC. If not defined 1487 a default value will be used. 1488 1489- CONFIG_SYS_SPD_BUS_NUM 1490 If SPD EEPROM is on an I2C bus other than the first 1491 one, specify here. Note that the value must resolve 1492 to something your driver can deal with. 1493 1494- CONFIG_FSL_DDR_INTERACTIVE 1495 Enable interactive DDR debugging. See doc/README.fsl-ddr. 1496 1497- CONFIG_FSL_DDR_SYNC_REFRESH 1498 Enable sync of refresh for multiple controllers. 1499 1500- CONFIG_FSL_DDR_BIST 1501 Enable built-in memory test for Freescale DDR controllers. 1502 1503- CONFIG_RMII 1504 Enable RMII mode for all FECs. 1505 Note that this is a global option, we can't 1506 have one FEC in standard MII mode and another in RMII mode. 1507 1508- CONFIG_CRC32_VERIFY 1509 Add a verify option to the crc32 command. 1510 The syntax is: 1511 1512 => crc32 -v <address> <count> <crc32> 1513 1514 Where address/count indicate a memory area 1515 and crc32 is the correct crc32 which the 1516 area should have. 1517 1518- CONFIG_LOOPW 1519 Add the "loopw" memory command. This only takes effect if 1520 the memory commands are activated globally (CONFIG_CMD_MEMORY). 1521 1522- CONFIG_CMD_MX_CYCLIC 1523 Add the "mdc" and "mwc" memory commands. These are cyclic 1524 "md/mw" commands. 1525 Examples: 1526 1527 => mdc.b 10 4 500 1528 This command will print 4 bytes (10,11,12,13) each 500 ms. 1529 1530 => mwc.l 100 12345678 10 1531 This command will write 12345678 to address 100 all 10 ms. 1532 1533 This only takes effect if the memory commands are activated 1534 globally (CONFIG_CMD_MEMORY). 1535 1536- CONFIG_SPL_BUILD 1537 Set when the currently running compilation is for an artifact 1538 that will end up in one of the 'xPL' builds, i.e. SPL, TPL or 1539 VPL. Code that needs phase-specific behaviour can check this, 1540 or (where possible) use spl_phase() instead. 1541 1542 Note that CONFIG_SPL_BUILD *is* always defined when either 1543 of CONFIG_TPL_BUILD / CONFIG_VPL_BUILD is defined. This can be 1544 counter-intuitive and should perhaps be changed. 1545 1546- CONFIG_TPL_BUILD 1547 Set when the currently running compilation is for an artifact 1548 that will end up in the TPL build (as opposed to SPL, VPL or 1549 U-Boot proper). Code that needs phase-specific behaviour can 1550 check this, or (where possible) use spl_phase() instead. 1551 1552- CONFIG_VPL_BUILD 1553 Set when the currently running compilation is for an artifact 1554 that will end up in the VPL build (as opposed to the SPL, TPL 1555 or U-Boot proper). Code that needs phase-specific behaviour can 1556 check this, or (where possible) use spl_phase() instead. 1557 1558- CONFIG_ARCH_MAP_SYSMEM 1559 Generally U-Boot (and in particular the md command) uses 1560 effective address. It is therefore not necessary to regard 1561 U-Boot address as virtual addresses that need to be translated 1562 to physical addresses. However, sandbox requires this, since 1563 it maintains its own little RAM buffer which contains all 1564 addressable memory. This option causes some memory accesses 1565 to be mapped through map_sysmem() / unmap_sysmem(). 1566 1567- CONFIG_X86_RESET_VECTOR 1568 If defined, the x86 reset vector code is included. This is not 1569 needed when U-Boot is running from Coreboot. 1570 1571Freescale QE/FMAN Firmware Support: 1572----------------------------------- 1573 1574The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the 1575loading of "firmware", which is encoded in the QE firmware binary format. 1576This firmware often needs to be loaded during U-Boot booting, so macros 1577are used to identify the storage device (NOR flash, SPI, etc) and the address 1578within that device. 1579 1580- CONFIG_SYS_FMAN_FW_ADDR 1581 The address in the storage device where the FMAN microcode is located. The 1582 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro 1583 is also specified. 1584 1585- CONFIG_SYS_QE_FW_ADDR 1586 The address in the storage device where the QE microcode is located. The 1587 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro 1588 is also specified. 1589 1590- CONFIG_SYS_QE_FMAN_FW_LENGTH 1591 The maximum possible size of the firmware. The firmware binary format 1592 has a field that specifies the actual size of the firmware, but it 1593 might not be possible to read any part of the firmware unless some 1594 local storage is allocated to hold the entire firmware first. 1595 1596- CONFIG_SYS_QE_FMAN_FW_IN_NOR 1597 Specifies that QE/FMAN firmware is located in NOR flash, mapped as 1598 normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the 1599 virtual address in NOR flash. 1600 1601- CONFIG_SYS_QE_FMAN_FW_IN_NAND 1602 Specifies that QE/FMAN firmware is located in NAND flash. 1603 CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash. 1604 1605- CONFIG_SYS_QE_FMAN_FW_IN_MMC 1606 Specifies that QE/FMAN firmware is located on the primary SD/MMC 1607 device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device. 1608 1609- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE 1610 Specifies that QE/FMAN firmware is located in the remote (master) 1611 memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which 1612 can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound 1613 window->master inbound window->master LAW->the ucode address in 1614 master's memory space. 1615 1616Freescale Layerscape Management Complex Firmware Support: 1617--------------------------------------------------------- 1618The Freescale Layerscape Management Complex (MC) supports the loading of 1619"firmware". 1620This firmware often needs to be loaded during U-Boot booting, so macros 1621are used to identify the storage device (NOR flash, SPI, etc) and the address 1622within that device. 1623 1624- CONFIG_FSL_MC_ENET 1625 Enable the MC driver for Layerscape SoCs. 1626 1627Freescale Layerscape Debug Server Support: 1628------------------------------------------- 1629The Freescale Layerscape Debug Server Support supports the loading of 1630"Debug Server firmware" and triggering SP boot-rom. 1631This firmware often needs to be loaded during U-Boot booting. 1632 1633- CONFIG_SYS_MC_RSV_MEM_ALIGN 1634 Define alignment of reserved memory MC requires 1635 1636 1637Building the Software: 1638====================== 1639 1640Building U-Boot has been tested in several native build environments 1641and in many different cross environments. Of course we cannot support 1642all possibly existing versions of cross development tools in all 1643(potentially obsolete) versions. In case of tool chain problems we 1644recommend to use the ELDK (see https://www.denx.de/wiki/DULG/ELDK) 1645which is extensively used to build and test U-Boot. 1646 1647If you are not using a native environment, it is assumed that you 1648have GNU cross compiling tools available in your path. In this case, 1649you must set the environment variable CROSS_COMPILE in your shell. 1650Note that no changes to the Makefile or any other source files are 1651necessary. For example using the ELDK on a 4xx CPU, please enter: 1652 1653 $ CROSS_COMPILE=ppc_4xx- 1654 $ export CROSS_COMPILE 1655 1656U-Boot is intended to be simple to build. After installing the 1657sources you must configure U-Boot for one specific board type. This 1658is done by typing: 1659 1660 make NAME_defconfig 1661 1662where "NAME_defconfig" is the name of one of the existing configu- 1663rations; see configs/*_defconfig for supported names. 1664 1665Note: for some boards special configuration names may exist; check if 1666 additional information is available from the board vendor; for 1667 instance, the TQM823L systems are available without (standard) 1668 or with LCD support. You can select such additional "features" 1669 when choosing the configuration, i. e. 1670 1671 make TQM823L_defconfig 1672 - will configure for a plain TQM823L, i. e. no LCD support 1673 1674 make TQM823L_LCD_defconfig 1675 - will configure for a TQM823L with U-Boot console on LCD 1676 1677 etc. 1678 1679 1680Finally, type "make all", and you should get some working U-Boot 1681images ready for download to / installation on your system: 1682 1683- "u-boot.bin" is a raw binary image 1684- "u-boot" is an image in ELF binary format 1685- "u-boot.srec" is in Motorola S-Record format 1686 1687By default the build is performed locally and the objects are saved 1688in the source directory. One of the two methods can be used to change 1689this behavior and build U-Boot to some external directory: 1690 16911. Add O= to the make command line invocations: 1692 1693 make O=/tmp/build distclean 1694 make O=/tmp/build NAME_defconfig 1695 make O=/tmp/build all 1696 16972. Set environment variable KBUILD_OUTPUT to point to the desired location: 1698 1699 export KBUILD_OUTPUT=/tmp/build 1700 make distclean 1701 make NAME_defconfig 1702 make all 1703 1704Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment 1705variable. 1706 1707User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by 1708setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS. 1709For example to treat all compiler warnings as errors: 1710 1711 make KCFLAGS=-Werror 1712 1713Please be aware that the Makefiles assume you are using GNU make, so 1714for instance on NetBSD you might need to use "gmake" instead of 1715native "make". 1716 1717 1718If the system board that you have is not listed, then you will need 1719to port U-Boot to your hardware platform. To do this, follow these 1720steps: 1721 17221. Create a new directory to hold your board specific code. Add any 1723 files you need. In your board directory, you will need at least 1724 the "Makefile" and a "<board>.c". 17252. Create a new configuration file "include/configs/<board>.h" for 1726 your board. 17273. If you're porting U-Boot to a new CPU, then also create a new 1728 directory to hold your CPU specific code. Add any files you need. 17294. Run "make <board>_defconfig" with your new name. 17305. Type "make", and you should get a working "u-boot.srec" file 1731 to be installed on your target system. 17326. Debug and solve any problems that might arise. 1733 [Of course, this last step is much harder than it sounds.] 1734 1735 1736Testing of U-Boot Modifications, Ports to New Hardware, etc.: 1737============================================================== 1738 1739If you have modified U-Boot sources (for instance added a new board 1740or support for new devices, a new CPU, etc.) you are expected to 1741provide feedback to the other developers. The feedback normally takes 1742the form of a "patch", i.e. a context diff against a certain (latest 1743official or latest in the git repository) version of U-Boot sources. 1744 1745But before you submit such a patch, please verify that your modifi- 1746cation did not break existing code. At least make sure that *ALL* of 1747the supported boards compile WITHOUT ANY compiler warnings. To do so, 1748just run the buildman script (tools/buildman/buildman), which will 1749configure and build U-Boot for ALL supported system. Be warned, this 1750will take a while. Please see the buildman README, or run 'buildman -H' 1751for documentation. 1752 1753 1754See also "U-Boot Porting Guide" below. 1755 1756 1757Monitor Commands - Overview: 1758============================ 1759 1760go - start application at address 'addr' 1761run - run commands in an environment variable 1762bootm - boot application image from memory 1763bootp - boot image via network using BootP/TFTP protocol 1764bootz - boot zImage from memory 1765tftpboot- boot image via network using TFTP protocol 1766 and env variables "ipaddr" and "serverip" 1767 (and eventually "gatewayip") 1768tftpput - upload a file via network using TFTP protocol 1769rarpboot- boot image via network using RARP/TFTP protocol 1770diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd' 1771loads - load S-Record file over serial line 1772loadb - load binary file over serial line (kermit mode) 1773loadm - load binary blob from source address to destination address 1774md - memory display 1775mm - memory modify (auto-incrementing) 1776nm - memory modify (constant address) 1777mw - memory write (fill) 1778ms - memory search 1779cp - memory copy 1780cmp - memory compare 1781crc32 - checksum calculation 1782i2c - I2C sub-system 1783sspi - SPI utility commands 1784base - print or set address offset 1785printenv- print environment variables 1786pwm - control pwm channels 1787seama - load SEAMA NAND image 1788setenv - set environment variables 1789saveenv - save environment variables to persistent storage 1790protect - enable or disable FLASH write protection 1791erase - erase FLASH memory 1792flinfo - print FLASH memory information 1793nand - NAND memory operations (see doc/README.nand) 1794bdinfo - print Board Info structure 1795iminfo - print header information for application image 1796coninfo - print console devices and informations 1797ide - IDE sub-system 1798loop - infinite loop on address range 1799loopw - infinite write loop on address range 1800mtest - simple RAM test 1801icache - enable or disable instruction cache 1802dcache - enable or disable data cache 1803reset - Perform RESET of the CPU 1804echo - echo args to console 1805version - print monitor version 1806help - print online help 1807? - alias for 'help' 1808 1809 1810Monitor Commands - Detailed Description: 1811======================================== 1812 1813TODO. 1814 1815For now: just type "help <command>". 1816 1817 1818Note for Redundant Ethernet Interfaces: 1819======================================= 1820 1821Some boards come with redundant Ethernet interfaces; U-Boot supports 1822such configurations and is capable of automatic selection of a 1823"working" interface when needed. MAC assignment works as follows: 1824 1825Network interfaces are numbered eth0, eth1, eth2, ... Corresponding 1826MAC addresses can be stored in the environment as "ethaddr" (=>eth0), 1827"eth1addr" (=>eth1), "eth2addr", ... 1828 1829If the network interface stores some valid MAC address (for instance 1830in SROM), this is used as default address if there is NO correspon- 1831ding setting in the environment; if the corresponding environment 1832variable is set, this overrides the settings in the card; that means: 1833 1834o If the SROM has a valid MAC address, and there is no address in the 1835 environment, the SROM's address is used. 1836 1837o If there is no valid address in the SROM, and a definition in the 1838 environment exists, then the value from the environment variable is 1839 used. 1840 1841o If both the SROM and the environment contain a MAC address, and 1842 both addresses are the same, this MAC address is used. 1843 1844o If both the SROM and the environment contain a MAC address, and the 1845 addresses differ, the value from the environment is used and a 1846 warning is printed. 1847 1848o If neither SROM nor the environment contain a MAC address, an error 1849 is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case 1850 a random, locally-assigned MAC is used. 1851 1852If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses 1853will be programmed into hardware as part of the initialization process. This 1854may be skipped by setting the appropriate 'ethmacskip' environment variable. 1855The naming convention is as follows: 1856"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc. 1857 1858Image Formats: 1859============== 1860 1861U-Boot is capable of booting (and performing other auxiliary operations on) 1862images in two formats: 1863 1864New uImage format (FIT) 1865----------------------- 1866 1867Flexible and powerful format based on Flattened Image Tree -- FIT (similar 1868to Flattened Device Tree). It allows the use of images with multiple 1869components (several kernels, ramdisks, etc.), with contents protected by 1870SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory. 1871 1872 1873Old uImage format 1874----------------- 1875 1876Old image format is based on binary files which can be basically anything, 1877preceded by a special header; see the definitions in include/image.h for 1878details; basically, the header defines the following image properties: 1879 1880* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD, 1881 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks, 1882 LynxOS, pSOS, QNX, RTEMS, INTEGRITY; 1883 Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, INTEGRITY). 1884* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86, 1885 IA64, MIPS, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit; 1886 Currently supported: ARM, Intel x86, MIPS, Nios II, PowerPC). 1887* Compression Type (uncompressed, gzip, bzip2) 1888* Load Address 1889* Entry Point 1890* Image Name 1891* Image Timestamp 1892 1893The header is marked by a special Magic Number, and both the header 1894and the data portions of the image are secured against corruption by 1895CRC32 checksums. 1896 1897 1898Linux Support: 1899============== 1900 1901Although U-Boot should support any OS or standalone application 1902easily, the main focus has always been on Linux during the design of 1903U-Boot. 1904 1905U-Boot includes many features that so far have been part of some 1906special "boot loader" code within the Linux kernel. Also, any 1907"initrd" images to be used are no longer part of one big Linux image; 1908instead, kernel and "initrd" are separate images. This implementation 1909serves several purposes: 1910 1911- the same features can be used for other OS or standalone 1912 applications (for instance: using compressed images to reduce the 1913 Flash memory footprint) 1914 1915- it becomes much easier to port new Linux kernel versions because 1916 lots of low-level, hardware dependent stuff are done by U-Boot 1917 1918- the same Linux kernel image can now be used with different "initrd" 1919 images; of course this also means that different kernel images can 1920 be run with the same "initrd". This makes testing easier (you don't 1921 have to build a new "zImage.initrd" Linux image when you just 1922 change a file in your "initrd"). Also, a field-upgrade of the 1923 software is easier now. 1924 1925 1926Linux HOWTO: 1927============ 1928 1929Porting Linux to U-Boot based systems: 1930--------------------------------------- 1931 1932U-Boot cannot save you from doing all the necessary modifications to 1933configure the Linux device drivers for use with your target hardware 1934(no, we don't intend to provide a full virtual machine interface to 1935Linux :-). 1936 1937But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot). 1938 1939Just make sure your machine specific header file (for instance 1940include/asm-ppc/tqm8xx.h) includes the same definition of the Board 1941Information structure as we define in include/asm-<arch>/u-boot.h, 1942and make sure that your definition of IMAP_ADDR uses the same value 1943as your U-Boot configuration in CONFIG_SYS_IMMR. 1944 1945Note that U-Boot now has a driver model, a unified model for drivers. 1946If you are adding a new driver, plumb it into driver model. If there 1947is no uclass available, you are encouraged to create one. See 1948doc/driver-model. 1949 1950 1951Configuring the Linux kernel: 1952----------------------------- 1953 1954No specific requirements for U-Boot. Make sure you have some root 1955device (initial ramdisk, NFS) for your target system. 1956 1957 1958Building a Linux Image: 1959----------------------- 1960 1961With U-Boot, "normal" build targets like "zImage" or "bzImage" are 1962not used. If you use recent kernel source, a new build target 1963"uImage" will exist which automatically builds an image usable by 1964U-Boot. Most older kernels also have support for a "pImage" target, 1965which was introduced for our predecessor project PPCBoot and uses a 1966100% compatible format. 1967 1968Example: 1969 1970 make TQM850L_defconfig 1971 make oldconfig 1972 make dep 1973 make uImage 1974 1975The "uImage" build target uses a special tool (in 'tools/mkimage') to 1976encapsulate a compressed Linux kernel image with header information, 1977CRC32 checksum etc. for use with U-Boot. This is what we are doing: 1978 1979* build a standard "vmlinux" kernel image (in ELF binary format): 1980 1981* convert the kernel into a raw binary image: 1982 1983 ${CROSS_COMPILE}-objcopy -O binary \ 1984 -R .note -R .comment \ 1985 -S vmlinux linux.bin 1986 1987* compress the binary image: 1988 1989 gzip -9 linux.bin 1990 1991* package compressed binary image for U-Boot: 1992 1993 mkimage -A ppc -O linux -T kernel -C gzip \ 1994 -a 0 -e 0 -n "Linux Kernel Image" \ 1995 -d linux.bin.gz uImage 1996 1997 1998The "mkimage" tool can also be used to create ramdisk images for use 1999with U-Boot, either separated from the Linux kernel image, or 2000combined into one file. "mkimage" encapsulates the images with a 64 2001byte header containing information about target architecture, 2002operating system, image type, compression method, entry points, time 2003stamp, CRC32 checksums, etc. 2004 2005"mkimage" can be called in two ways: to verify existing images and 2006print the header information, or to build new images. 2007 2008In the first form (with "-l" option) mkimage lists the information 2009contained in the header of an existing U-Boot image; this includes 2010checksum verification: 2011 2012 tools/mkimage -l image 2013 -l ==> list image header information 2014 2015The second form (with "-d" option) is used to build a U-Boot image 2016from a "data file" which is used as image payload: 2017 2018 tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \ 2019 -n name -d data_file image 2020 -A ==> set architecture to 'arch' 2021 -O ==> set operating system to 'os' 2022 -T ==> set image type to 'type' 2023 -C ==> set compression type 'comp' 2024 -a ==> set load address to 'addr' (hex) 2025 -e ==> set entry point to 'ep' (hex) 2026 -n ==> set image name to 'name' 2027 -d ==> use image data from 'datafile' 2028 2029Right now, all Linux kernels for PowerPC systems use the same load 2030address (0x00000000), but the entry point address depends on the 2031kernel version: 2032 2033- 2.2.x kernels have the entry point at 0x0000000C, 2034- 2.3.x and later kernels have the entry point at 0x00000000. 2035 2036So a typical call to build a U-Boot image would read: 2037 2038 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \ 2039 > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \ 2040 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \ 2041 > examples/uImage.TQM850L 2042 Image Name: 2.4.4 kernel for TQM850L 2043 Created: Wed Jul 19 02:34:59 2000 2044 Image Type: PowerPC Linux Kernel Image (gzip compressed) 2045 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB 2046 Load Address: 0x00000000 2047 Entry Point: 0x00000000 2048 2049To verify the contents of the image (or check for corruption): 2050 2051 -> tools/mkimage -l examples/uImage.TQM850L 2052 Image Name: 2.4.4 kernel for TQM850L 2053 Created: Wed Jul 19 02:34:59 2000 2054 Image Type: PowerPC Linux Kernel Image (gzip compressed) 2055 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB 2056 Load Address: 0x00000000 2057 Entry Point: 0x00000000 2058 2059NOTE: for embedded systems where boot time is critical you can trade 2060speed for memory and install an UNCOMPRESSED image instead: this 2061needs more space in Flash, but boots much faster since it does not 2062need to be uncompressed: 2063 2064 -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz 2065 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \ 2066 > -A ppc -O linux -T kernel -C none -a 0 -e 0 \ 2067 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \ 2068 > examples/uImage.TQM850L-uncompressed 2069 Image Name: 2.4.4 kernel for TQM850L 2070 Created: Wed Jul 19 02:34:59 2000 2071 Image Type: PowerPC Linux Kernel Image (uncompressed) 2072 Data Size: 792160 Bytes = 773.59 kB = 0.76 MB 2073 Load Address: 0x00000000 2074 Entry Point: 0x00000000 2075 2076 2077Similar you can build U-Boot images from a 'ramdisk.image.gz' file 2078when your kernel is intended to use an initial ramdisk: 2079 2080 -> tools/mkimage -n 'Simple Ramdisk Image' \ 2081 > -A ppc -O linux -T ramdisk -C gzip \ 2082 > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd 2083 Image Name: Simple Ramdisk Image 2084 Created: Wed Jan 12 14:01:50 2000 2085 Image Type: PowerPC Linux RAMDisk Image (gzip compressed) 2086 Data Size: 566530 Bytes = 553.25 kB = 0.54 MB 2087 Load Address: 0x00000000 2088 Entry Point: 0x00000000 2089 2090The "dumpimage" tool can be used to disassemble or list the contents of images 2091built by mkimage. See dumpimage's help output (-h) for details. 2092 2093Installing a Linux Image: 2094------------------------- 2095 2096To downloading a U-Boot image over the serial (console) interface, 2097you must convert the image to S-Record format: 2098 2099 objcopy -I binary -O srec examples/image examples/image.srec 2100 2101The 'objcopy' does not understand the information in the U-Boot 2102image header, so the resulting S-Record file will be relative to 2103address 0x00000000. To load it to a given address, you need to 2104specify the target address as 'offset' parameter with the 'loads' 2105command. 2106 2107Example: install the image to address 0x40100000 (which on the 2108TQM8xxL is in the first Flash bank): 2109 2110 => erase 40100000 401FFFFF 2111 2112 .......... done 2113 Erased 8 sectors 2114 2115 => loads 40100000 2116 ## Ready for S-Record download ... 2117 ~>examples/image.srec 2118 1 2 3 4 5 6 7 8 9 10 11 12 13 ... 2119 ... 2120 15989 15990 15991 15992 2121 [file transfer complete] 2122 [connected] 2123 ## Start Addr = 0x00000000 2124 2125 2126You can check the success of the download using the 'iminfo' command; 2127this includes a checksum verification so you can be sure no data 2128corruption happened: 2129 2130 => imi 40100000 2131 2132 ## Checking Image at 40100000 ... 2133 Image Name: 2.2.13 for initrd on TQM850L 2134 Image Type: PowerPC Linux Kernel Image (gzip compressed) 2135 Data Size: 335725 Bytes = 327 kB = 0 MB 2136 Load Address: 00000000 2137 Entry Point: 0000000c 2138 Verifying Checksum ... OK 2139 2140 2141Boot Linux: 2142----------- 2143 2144The "bootm" command is used to boot an application that is stored in 2145memory (RAM or Flash). In case of a Linux kernel image, the contents 2146of the "bootargs" environment variable is passed to the kernel as 2147parameters. You can check and modify this variable using the 2148"printenv" and "setenv" commands: 2149 2150 2151 => printenv bootargs 2152 bootargs=root=/dev/ram 2153 2154 => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2 2155 2156 => printenv bootargs 2157 bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2 2158 2159 => bootm 40020000 2160 ## Booting Linux kernel at 40020000 ... 2161 Image Name: 2.2.13 for NFS on TQM850L 2162 Image Type: PowerPC Linux Kernel Image (gzip compressed) 2163 Data Size: 381681 Bytes = 372 kB = 0 MB 2164 Load Address: 00000000 2165 Entry Point: 0000000c 2166 Verifying Checksum ... OK 2167 Uncompressing Kernel Image ... OK 2168 Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000 2169 Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2 2170 time_init: decrementer frequency = 187500000/60 2171 Calibrating delay loop... 49.77 BogoMIPS 2172 Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000] 2173 ... 2174 2175If you want to boot a Linux kernel with initial RAM disk, you pass 2176the memory addresses of both the kernel and the initrd image (PPBCOOT 2177format!) to the "bootm" command: 2178 2179 => imi 40100000 40200000 2180 2181 ## Checking Image at 40100000 ... 2182 Image Name: 2.2.13 for initrd on TQM850L 2183 Image Type: PowerPC Linux Kernel Image (gzip compressed) 2184 Data Size: 335725 Bytes = 327 kB = 0 MB 2185 Load Address: 00000000 2186 Entry Point: 0000000c 2187 Verifying Checksum ... OK 2188 2189 ## Checking Image at 40200000 ... 2190 Image Name: Simple Ramdisk Image 2191 Image Type: PowerPC Linux RAMDisk Image (gzip compressed) 2192 Data Size: 566530 Bytes = 553 kB = 0 MB 2193 Load Address: 00000000 2194 Entry Point: 00000000 2195 Verifying Checksum ... OK 2196 2197 => bootm 40100000 40200000 2198 ## Booting Linux kernel at 40100000 ... 2199 Image Name: 2.2.13 for initrd on TQM850L 2200 Image Type: PowerPC Linux Kernel Image (gzip compressed) 2201 Data Size: 335725 Bytes = 327 kB = 0 MB 2202 Load Address: 00000000 2203 Entry Point: 0000000c 2204 Verifying Checksum ... OK 2205 Uncompressing Kernel Image ... OK 2206 ## Loading RAMDisk Image at 40200000 ... 2207 Image Name: Simple Ramdisk Image 2208 Image Type: PowerPC Linux RAMDisk Image (gzip compressed) 2209 Data Size: 566530 Bytes = 553 kB = 0 MB 2210 Load Address: 00000000 2211 Entry Point: 00000000 2212 Verifying Checksum ... OK 2213 Loading Ramdisk ... OK 2214 Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000 2215 Boot arguments: root=/dev/ram 2216 time_init: decrementer frequency = 187500000/60 2217 Calibrating delay loop... 49.77 BogoMIPS 2218 ... 2219 RAMDISK: Compressed image found at block 0 2220 VFS: Mounted root (ext2 filesystem). 2221 2222 bash# 2223 2224Boot Linux and pass a flat device tree: 2225----------- 2226 2227First, U-Boot must be compiled with the appropriate defines. See the section 2228titled "Linux Kernel Interface" above for a more in depth explanation. The 2229following is an example of how to start a kernel and pass an updated 2230flat device tree: 2231 2232=> print oftaddr 2233oftaddr=0x300000 2234=> print oft 2235oft=oftrees/mpc8540ads.dtb 2236=> tftp $oftaddr $oft 2237Speed: 1000, full duplex 2238Using TSEC0 device 2239TFTP from server 192.168.1.1; our IP address is 192.168.1.101 2240Filename 'oftrees/mpc8540ads.dtb'. 2241Load address: 0x300000 2242Loading: # 2243done 2244Bytes transferred = 4106 (100a hex) 2245=> tftp $loadaddr $bootfile 2246Speed: 1000, full duplex 2247Using TSEC0 device 2248TFTP from server 192.168.1.1; our IP address is 192.168.1.2 2249Filename 'uImage'. 2250Load address: 0x200000 2251Loading:############ 2252done 2253Bytes transferred = 1029407 (fb51f hex) 2254=> print loadaddr 2255loadaddr=200000 2256=> print oftaddr 2257oftaddr=0x300000 2258=> bootm $loadaddr - $oftaddr 2259## Booting image at 00200000 ... 2260 Image Name: Linux-2.6.17-dirty 2261 Image Type: PowerPC Linux Kernel Image (gzip compressed) 2262 Data Size: 1029343 Bytes = 1005.2 kB 2263 Load Address: 00000000 2264 Entry Point: 00000000 2265 Verifying Checksum ... OK 2266 Uncompressing Kernel Image ... OK 2267Booting using flat device tree at 0x300000 2268Using MPC85xx ADS machine description 2269Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb 2270[snip] 2271 2272 2273More About U-Boot Image Types: 2274------------------------------ 2275 2276U-Boot supports the following image types: 2277 2278 "Standalone Programs" are directly runnable in the environment 2279 provided by U-Boot; it is expected that (if they behave 2280 well) you can continue to work in U-Boot after return from 2281 the Standalone Program. 2282 "OS Kernel Images" are usually images of some Embedded OS which 2283 will take over control completely. Usually these programs 2284 will install their own set of exception handlers, device 2285 drivers, set up the MMU, etc. - this means, that you cannot 2286 expect to re-enter U-Boot except by resetting the CPU. 2287 "RAMDisk Images" are more or less just data blocks, and their 2288 parameters (address, size) are passed to an OS kernel that is 2289 being started. 2290 "Multi-File Images" contain several images, typically an OS 2291 (Linux) kernel image and one or more data images like 2292 RAMDisks. This construct is useful for instance when you want 2293 to boot over the network using BOOTP etc., where the boot 2294 server provides just a single image file, but you want to get 2295 for instance an OS kernel and a RAMDisk image. 2296 2297 "Multi-File Images" start with a list of image sizes, each 2298 image size (in bytes) specified by an "uint32_t" in network 2299 byte order. This list is terminated by an "(uint32_t)0". 2300 Immediately after the terminating 0 follow the images, one by 2301 one, all aligned on "uint32_t" boundaries (size rounded up to 2302 a multiple of 4 bytes). 2303 2304 "Firmware Images" are binary images containing firmware (like 2305 U-Boot or FPGA images) which usually will be programmed to 2306 flash memory. 2307 2308 "Script files" are command sequences that will be executed by 2309 U-Boot's command interpreter; this feature is especially 2310 useful when you configure U-Boot to use a real shell (hush) 2311 as command interpreter. 2312 2313Booting the Linux zImage: 2314------------------------- 2315 2316On some platforms, it's possible to boot Linux zImage. This is done 2317using the "bootz" command. The syntax of "bootz" command is the same 2318as the syntax of "bootm" command. 2319 2320Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply 2321kernel with raw initrd images. The syntax is slightly different, the 2322address of the initrd must be augmented by it's size, in the following 2323format: "<initrd addres>:<initrd size>". 2324 2325 2326Standalone HOWTO: 2327================= 2328 2329One of the features of U-Boot is that you can dynamically load and 2330run "standalone" applications, which can use some resources of 2331U-Boot like console I/O functions or interrupt services. 2332 2333Two simple examples are included with the sources: 2334 2335"Hello World" Demo: 2336------------------- 2337 2338'examples/hello_world.c' contains a small "Hello World" Demo 2339application; it is automatically compiled when you build U-Boot. 2340It's configured to run at address 0x00040004, so you can play with it 2341like that: 2342 2343 => loads 2344 ## Ready for S-Record download ... 2345 ~>examples/hello_world.srec 2346 1 2 3 4 5 6 7 8 9 10 11 ... 2347 [file transfer complete] 2348 [connected] 2349 ## Start Addr = 0x00040004 2350 2351 => go 40004 Hello World! This is a test. 2352 ## Starting application at 0x00040004 ... 2353 Hello World 2354 argc = 7 2355 argv[0] = "40004" 2356 argv[1] = "Hello" 2357 argv[2] = "World!" 2358 argv[3] = "This" 2359 argv[4] = "is" 2360 argv[5] = "a" 2361 argv[6] = "test." 2362 argv[7] = "<NULL>" 2363 Hit any key to exit ... 2364 2365 ## Application terminated, rc = 0x0 2366 2367Another example, which demonstrates how to register a CPM interrupt 2368handler with the U-Boot code, can be found in 'examples/timer.c'. 2369Here, a CPM timer is set up to generate an interrupt every second. 2370The interrupt service routine is trivial, just printing a '.' 2371character, but this is just a demo program. The application can be 2372controlled by the following keys: 2373 2374 ? - print current values og the CPM Timer registers 2375 b - enable interrupts and start timer 2376 e - stop timer and disable interrupts 2377 q - quit application 2378 2379 => loads 2380 ## Ready for S-Record download ... 2381 ~>examples/timer.srec 2382 1 2 3 4 5 6 7 8 9 10 11 ... 2383 [file transfer complete] 2384 [connected] 2385 ## Start Addr = 0x00040004 2386 2387 => go 40004 2388 ## Starting application at 0x00040004 ... 2389 TIMERS=0xfff00980 2390 Using timer 1 2391 tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0 2392 2393Hit 'b': 2394 [q, b, e, ?] Set interval 1000000 us 2395 Enabling timer 2396Hit '?': 2397 [q, b, e, ?] ........ 2398 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0 2399Hit '?': 2400 [q, b, e, ?] . 2401 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0 2402Hit '?': 2403 [q, b, e, ?] . 2404 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0 2405Hit '?': 2406 [q, b, e, ?] . 2407 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0 2408Hit 'e': 2409 [q, b, e, ?] ...Stopping timer 2410Hit 'q': 2411 [q, b, e, ?] ## Application terminated, rc = 0x0 2412 2413 2414Implementation Internals: 2415========================= 2416 2417The following is not intended to be a complete description of every 2418implementation detail. However, it should help to understand the 2419inner workings of U-Boot and make it easier to port it to custom 2420hardware. 2421 2422 2423Initial Stack, Global Data: 2424--------------------------- 2425 2426The implementation of U-Boot is complicated by the fact that U-Boot 2427starts running out of ROM (flash memory), usually without access to 2428system RAM (because the memory controller is not initialized yet). 2429This means that we don't have writable Data or BSS segments, and BSS 2430is not initialized as zero. To be able to get a C environment working 2431at all, we have to allocate at least a minimal stack. Implementation 2432options for this are defined and restricted by the CPU used: Some CPU 2433models provide on-chip memory (like the IMMR area on MPC8xx and 2434MPC826x processors), on others (parts of) the data cache can be 2435locked as (mis-) used as memory, etc. 2436 2437 Chris Hallinan posted a good summary of these issues to the 2438 U-Boot mailing list: 2439 2440 Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)? 2441 From: "Chris Hallinan" <clh@net1plus.com> 2442 Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET) 2443 ... 2444 2445 Correct me if I'm wrong, folks, but the way I understand it 2446 is this: Using DCACHE as initial RAM for Stack, etc, does not 2447 require any physical RAM backing up the cache. The cleverness 2448 is that the cache is being used as a temporary supply of 2449 necessary storage before the SDRAM controller is setup. It's 2450 beyond the scope of this list to explain the details, but you 2451 can see how this works by studying the cache architecture and 2452 operation in the architecture and processor-specific manuals. 2453 2454 OCM is On Chip Memory, which I believe the 405GP has 4K. It 2455 is another option for the system designer to use as an 2456 initial stack/RAM area prior to SDRAM being available. Either 2457 option should work for you. Using CS 4 should be fine if your 2458 board designers haven't used it for something that would 2459 cause you grief during the initial boot! It is frequently not 2460 used. 2461 2462 CFG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere 2463 with your processor/board/system design. The default value 2464 you will find in any recent u-boot distribution in 2465 walnut.h should work for you. I'd set it to a value larger 2466 than your SDRAM module. If you have a 64MB SDRAM module, set 2467 it above 400_0000. Just make sure your board has no resources 2468 that are supposed to respond to that address! That code in 2469 start.S has been around a while and should work as is when 2470 you get the config right. 2471 2472 -Chris Hallinan 2473 DS4.COM, Inc. 2474 2475It is essential to remember this, since it has some impact on the C 2476code for the initialization procedures: 2477 2478* Initialized global data (data segment) is read-only. Do not attempt 2479 to write it. 2480 2481* Do not use any uninitialized global data (or implicitly initialized 2482 as zero data - BSS segment) at all - this is undefined, initiali- 2483 zation is performed later (when relocating to RAM). 2484 2485* Stack space is very limited. Avoid big data buffers or things like 2486 that. 2487 2488Having only the stack as writable memory limits means we cannot use 2489normal global data to share information between the code. But it 2490turned out that the implementation of U-Boot can be greatly 2491simplified by making a global data structure (gd_t) available to all 2492functions. We could pass a pointer to this data as argument to _all_ 2493functions, but this would bloat the code. Instead we use a feature of 2494the GCC compiler (Global Register Variables) to share the data: we 2495place a pointer (gd) to the global data into a register which we 2496reserve for this purpose. 2497 2498When choosing a register for such a purpose we are restricted by the 2499relevant (E)ABI specifications for the current architecture, and by 2500GCC's implementation. 2501 2502For PowerPC, the following registers have specific use: 2503 R1: stack pointer 2504 R2: reserved for system use 2505 R3-R4: parameter passing and return values 2506 R5-R10: parameter passing 2507 R13: small data area pointer 2508 R30: GOT pointer 2509 R31: frame pointer 2510 2511 (U-Boot also uses R12 as internal GOT pointer. r12 2512 is a volatile register so r12 needs to be reset when 2513 going back and forth between asm and C) 2514 2515 ==> U-Boot will use R2 to hold a pointer to the global data 2516 2517 Note: on PPC, we could use a static initializer (since the 2518 address of the global data structure is known at compile time), 2519 but it turned out that reserving a register results in somewhat 2520 smaller code - although the code savings are not that big (on 2521 average for all boards 752 bytes for the whole U-Boot image, 2522 624 text + 127 data). 2523 2524On ARM, the following registers are used: 2525 2526 R0: function argument word/integer result 2527 R1-R3: function argument word 2528 R9: platform specific 2529 R10: stack limit (used only if stack checking is enabled) 2530 R11: argument (frame) pointer 2531 R12: temporary workspace 2532 R13: stack pointer 2533 R14: link register 2534 R15: program counter 2535 2536 ==> U-Boot will use R9 to hold a pointer to the global data 2537 2538 Note: on ARM, only R_ARM_RELATIVE relocations are supported. 2539 2540On Nios II, the ABI is documented here: 2541 https://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf 2542 2543 ==> U-Boot will use gp to hold a pointer to the global data 2544 2545 Note: on Nios II, we give "-G0" option to gcc and don't use gp 2546 to access small data sections, so gp is free. 2547 2548On RISC-V, the following registers are used: 2549 2550 x0: hard-wired zero (zero) 2551 x1: return address (ra) 2552 x2: stack pointer (sp) 2553 x3: global pointer (gp) 2554 x4: thread pointer (tp) 2555 x5: link register (t0) 2556 x8: frame pointer (fp) 2557 x10-x11: arguments/return values (a0-1) 2558 x12-x17: arguments (a2-7) 2559 x28-31: temporaries (t3-6) 2560 pc: program counter (pc) 2561 2562 ==> U-Boot will use gp to hold a pointer to the global data 2563 2564Memory Management: 2565------------------ 2566 2567U-Boot runs in system state and uses physical addresses, i.e. the 2568MMU is not used either for address mapping nor for memory protection. 2569 2570The available memory is mapped to fixed addresses using the memory 2571controller. In this process, a contiguous block is formed for each 2572memory type (Flash, SDRAM, SRAM), even when it consists of several 2573physical memory banks. 2574 2575U-Boot is installed in the first 128 kB of the first Flash bank (on 2576TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After 2577booting and sizing and initializing DRAM, the code relocates itself 2578to the upper end of DRAM. Immediately below the U-Boot code some 2579memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN 2580configuration setting]. Below that, a structure with global Board 2581Info data is placed, followed by the stack (growing downward). 2582 2583Additionally, some exception handler code is copied to the low 8 kB 2584of DRAM (0x00000000 ... 0x00001FFF). 2585 2586So a typical memory configuration with 16 MB of DRAM could look like 2587this: 2588 2589 0x0000 0000 Exception Vector code 2590 : 2591 0x0000 1FFF 2592 0x0000 2000 Free for Application Use 2593 : 2594 : 2595 2596 : 2597 : 2598 0x00FB FF20 Monitor Stack (Growing downward) 2599 0x00FB FFAC Board Info Data and permanent copy of global data 2600 0x00FC 0000 Malloc Arena 2601 : 2602 0x00FD FFFF 2603 0x00FE 0000 RAM Copy of Monitor Code 2604 ... eventually: LCD or video framebuffer 2605 ... eventually: pRAM (Protected RAM - unchanged by reset) 2606 0x00FF FFFF [End of RAM] 2607 2608 2609System Initialization: 2610---------------------- 2611 2612In the reset configuration, U-Boot starts at the reset entry point 2613(on most PowerPC systems at address 0x00000100). Because of the reset 2614configuration for CS0# this is a mirror of the on board Flash memory. 2615To be able to re-map memory U-Boot then jumps to its link address. 2616To be able to implement the initialization code in C, a (small!) 2617initial stack is set up in the internal Dual Ported RAM (in case CPUs 2618which provide such a feature like), or in a locked part of the data 2619cache. After that, U-Boot initializes the CPU core, the caches and 2620the SIU. 2621 2622Next, all (potentially) available memory banks are mapped using a 2623preliminary mapping. For example, we put them on 512 MB boundaries 2624(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash 2625on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is 2626programmed for SDRAM access. Using the temporary configuration, a 2627simple memory test is run that determines the size of the SDRAM 2628banks. 2629 2630When there is more than one SDRAM bank, and the banks are of 2631different size, the largest is mapped first. For equal size, the first 2632bank (CS2#) is mapped first. The first mapping is always for address 26330x00000000, with any additional banks following immediately to create 2634contiguous memory starting from 0. 2635 2636Then, the monitor installs itself at the upper end of the SDRAM area 2637and allocates memory for use by malloc() and for the global Board 2638Info data; also, the exception vector code is copied to the low RAM 2639pages, and the final stack is set up. 2640 2641Only after this relocation will you have a "normal" C environment; 2642until that you are restricted in several ways, mostly because you are 2643running from ROM, and because the code will have to be relocated to a 2644new address in RAM. 2645 2646 2647Contributing 2648============ 2649 2650The U-Boot projects depends on contributions from the user community. 2651If you want to participate, please, have a look at the 'General' 2652section of https://docs.u-boot.org/en/latest/develop/index.html 2653where we describe coding standards and the patch submission process. 2654