U-Boot for Freescale i.MX6 This file contains information for the port of U-Boot to the Freescale i.MX6 SoC. 1. CONVENTIONS FOR FUSE ASSIGNMENTS ----------------------------------- 1.1 MAC Address: It is stored in fuse bank 4, with the 32 lsbs in word 2 and the 16 msbs in word 3[15:0]. For i.MX6SX and i.MX6UL, they have two MAC addresses. The second MAC address is stored in fuse bank 4, with the 16 lsb in word 3[31:16] and the 32 msbs in word 4. Example: For reading the MAC address fuses on a MX6Q: - The MAC address is stored in two fuse addresses (the fuse addresses are described in the Fusemap Descriptions table from the mx6q Reference Manual): 0x620[31:0] - MAC_ADDR[31:0] 0x630[15:0] - MAC_ADDR[47:32] In order to use the fuse API, we need to pass the bank and word values, which are calculated as below: Fuse address for the lower MAC address: 0x620 Base address for the fuses: 0x400 (0x620 - 0x400)/0x10 = 0x22 = 34 decimal As the fuses are arranged in banks of 8 words: 34 / 8 = 4 and the remainder is 2, so in this case: bank = 4 word = 2 And the U-Boot command would be: => fuse read 4 2 Reading bank 4: Word 0x00000002: 9f027772 Doing the same for the upper MAC address: Fuse address for the upper MAC address: 0x630 Base address for the fuses: 0x400 (0x630 - 0x400)/0x10 = 0x23 = 35 decimal As the fuses are arranged in banks of 8 words: 35 / 8 = 4 and the remainder is 3, so in this case: bank = 4 word = 3 And the U-Boot command would be: => fuse read 4 3 Reading bank 4: Word 0x00000003: 00000004 ,which matches the ethaddr value: => echo ${ethaddr} 00:04:9f:02:77:72 Some other useful hints: - The 'bank' and 'word' numbers can be easily obtained from the mx6 Reference Manual. For the mx6quad case, please check the "46.5 OCOTP Memory Map/Register Definition" from the "i.MX 6Dual/6Quad Applications Processor Reference Manual, Rev. 1, 04/2013" document. For example, for the MAC fuses we have: Address: 21B_C620 Value of OTP Bank4 Word2 (MAC Address)(OCOTP_MAC0) 21B_C630 Value of OTP Bank4 Word3 (MAC Address)(OCOTP_MAC1) - The command '=> fuse read 4 2 2' reads the whole MAC addresses at once: => fuse read 4 2 2 Reading bank 4: Word 0x00000002: 9f027772 00000004 NAND Boot on i.MX6 with SPL support -------------------------------------- Writing/updating boot image in nand device is not straight forward in i.MX6 platform and it requires boot control block(BCB) to be configured. BCB contains two data structures, Firmware Configuration Block(FCB) and Discovered Bad Block Table(DBBT). FCB has nand timings, DBBT search area, and firmware. See IMX6DQRM Section 8.5.2.2 for more information. We can't use 'nand write' command to write SPL/firmware image directly like other platforms does. So we need special setup to write BCB block as per IMX6QDL reference manual 'nandbcb update' command do that job. for nand boot, up on reset bootrom look for FCB structure in first block's if FCB found the nand timings are loaded for further reads. once FCB read done, DTTB will be loaded and finally firmware will be loaded which is boot image. cmd_nandbcb will create FCB these structures by taking mtd partition as an example. - initial code will erase entire partition - followed by FCB setup, like first 2 blocks for FCB/DBBT write, and next block for FW1/SPL - write firmware at FW1 block and - finally write fcb/dttb in first 2 block. Typical NAND BCB layout: ======================= no.of blocks = partition size / erasesize no.of fcb/dbbt blocks = 2 FW1 offset = no.of fcb/dbbt block 0 1 2 ------------------------------- |FCB/DBBT 0|FCB/DBBT 1| FW 1 | -------------------------------- On summary, nandbcb update will - erase the entire partition - create BCB by creating 2 FCB/BDDT block followed by 1 FW blocks based on partition size and erasesize. - fill FCB/DBBT structures - write FW/SPL in FW1 - write FCB/DBBT in first 2 blocks step-1: write SPL icorem6qdl> ext4load mmc 0:1 $loadaddr SPL 39936 bytes read in 10 ms (3.8 MiB/s) icorem6qdl> nandbcb update $loadaddr spl $filesize device 0 offset 0x0, size 0x9c00 Erasing at 0x1c0000 -- 100% complete. NAND fw write: 0x80000 offset, 0xb000 bytes written: OK step-2: write u-boot-dtb.img icorem6qdl> nand erase.part uboot NAND erase.part: device 0 offset 0x200000, size 0x200000 Erasing at 0x3c0000 -- 100% complete. OK icorem6qdl> ext4load mmc 0:1 $loadaddr u-boot-dtb.img 589094 bytes read in 37 ms (15.2 MiB/s) icorem6qdl> nand write ${loadaddr} uboot ${filesize} NAND write: device 0 offset 0x200000, size 0x8fd26 589094 bytes written: OK icorem6qdl> SPL Stack size and location notes --------------------------------- If we have CONFIG_MX6_OCRAM_256KB then see Figure 8.4.1 in IMX6DQ Reference manuals: - IMX6DQ OCRAM (IRAM) is from 0x00907000 to 0x0093FFFF - BOOT ROM stack is at 0x0093FFB8 - if icache/dcache is enabled (eFuse/strapping controlled) then the IMX BOOT ROM will setup MMU table at 0x00938000, therefore we need to fit between 0x00907000 and 0x00938000. - Additionally the BOOT ROM loads what they consider the firmware image which consists of a 4K header in front of us that contains the IVT, DCD and some padding thus 'our' max size is really 0x00908000 - 0x00938000 or 192KB - Pad SPL to 196KB (4KB header + 192KB max size). This allows to write the SPL/U-Boot combination generated with u-boot-with-spl.imx directly to a boot media (given that boot media specific offset is configured properly). and if we don't, see Figure 8-3 in IMX6SDL Reference manuals: - IMX6SDL OCRAM (IRAM) is from 0x00907000 to 0x0091FFFF - BOOT ROM stack is at 0x0091FFB8 - if icache/dcache is enabled (eFuse/strapping controlled) then the IMX BOOT ROM will setup MMU table at 0x00918000, therefore we need to fit between 0x00907000 and 0x00918000. - Additionally the BOOT ROM loads what they consider the firmware image which consists of a 4K header in front of us that contains the IVT, DCD and some padding thus 'our' max size is really 0x00908000 - 0x00918000 or 64KB - Pad SPL to 68KB (4KB header + 64KB max size). This allows to write the SPL/U-Boot combination generated with u-boot-with-spl.imx directly to a boot media (given that boot media specific offset is configured properly).