1Kernel driver i2c-piix4 2 3Supported adapters: 4 * Intel 82371AB PIIX4 and PIIX4E 5 * Intel 82443MX (440MX) 6 Datasheet: Publicly available at the Intel website 7 * ServerWorks OSB4, CSB5, CSB6 and HT-1000 southbridges 8 Datasheet: Only available via NDA from ServerWorks 9 * ATI IXP200, IXP300, IXP400 and SB600 southbridges 10 Datasheet: Not publicly available 11 * Standard Microsystems (SMSC) SLC90E66 (Victory66) southbridge 12 Datasheet: Publicly available at the SMSC website http://www.smsc.com 13 14Authors: 15 Frodo Looijaard <frodol@dds.nl> 16 Philip Edelbrock <phil@netroedge.com> 17 18 19Module Parameters 20----------------- 21 22* force: int 23 Forcibly enable the PIIX4. DANGEROUS! 24* force_addr: int 25 Forcibly enable the PIIX4 at the given address. EXTREMELY DANGEROUS! 26 27 28Description 29----------- 30 31The PIIX4 (properly known as the 82371AB) is an Intel chip with a lot of 32functionality. Among other things, it implements the PCI bus. One of its 33minor functions is implementing a System Management Bus. This is a true 34SMBus - you can not access it on I2C levels. The good news is that it 35natively understands SMBus commands and you do not have to worry about 36timing problems. The bad news is that non-SMBus devices connected to it can 37confuse it mightily. Yes, this is known to happen... 38 39Do 'lspci -v' and see whether it contains an entry like this: 40 410000:00:02.3 Bridge: Intel Corp. 82371AB/EB/MB PIIX4 ACPI (rev 02) 42 Flags: medium devsel, IRQ 9 43 44Bus and device numbers may differ, but the function number must be 45identical (like many PCI devices, the PIIX4 incorporates a number of 46different 'functions', which can be considered as separate devices). If you 47find such an entry, you have a PIIX4 SMBus controller. 48 49On some computers (most notably, some Dells), the SMBus is disabled by 50default. If you use the insmod parameter 'force=1', the kernel module will 51try to enable it. THIS IS VERY DANGEROUS! If the BIOS did not set up a 52correct address for this module, you could get in big trouble (read: 53crashes, data corruption, etc.). Try this only as a last resort (try BIOS 54updates first, for example), and backup first! An even more dangerous 55option is 'force_addr=<IOPORT>'. This will not only enable the PIIX4 like 56'force' foes, but it will also set a new base I/O port address. The SMBus 57parts of the PIIX4 needs a range of 8 of these addresses to function 58correctly. If these addresses are already reserved by some other device, 59you will get into big trouble! DON'T USE THIS IF YOU ARE NOT VERY SURE 60ABOUT WHAT YOU ARE DOING! 61 62The PIIX4E is just an new version of the PIIX4; it is supported as well. 63The PIIX/PIIX3 does not implement an SMBus or I2C bus, so you can't use 64this driver on those mainboards. 65 66The ServerWorks Southbridges, the Intel 440MX, and the Victory66 are 67identical to the PIIX4 in I2C/SMBus support. 68 69If you own Force CPCI735 motherboard or other OSB4 based systems you may need 70to change the SMBus Interrupt Select register so the SMBus controller uses 71the SMI mode. 72 731) Use lspci command and locate the PCI device with the SMBus controller: 74 00:0f.0 ISA bridge: ServerWorks OSB4 South Bridge (rev 4f) 75 The line may vary for different chipsets. Please consult the driver source 76 for all possible PCI ids (and lspci -n to match them). Lets assume the 77 device is located at 00:0f.0. 782) Now you just need to change the value in 0xD2 register. Get it first with 79 command: lspci -xxx -s 00:0f.0 80 If the value is 0x3 then you need to change it to 0x1 81 setpci -s 00:0f.0 d2.b=1 82 83Please note that you don't need to do that in all cases, just when the SMBus is 84not working properly. 85 86 87Hardware-specific issues 88------------------------ 89 90This driver will refuse to load on IBM systems with an Intel PIIX4 SMBus. 91Some of these machines have an RFID EEPROM (24RF08) connected to the SMBus, 92which can easily get corrupted due to a state machine bug. These are mostly 93Thinkpad laptops, but desktop systems may also be affected. We have no list 94of all affected systems, so the only safe solution was to prevent access to 95the SMBus on all IBM systems (detected using DMI data.) 96 97For additional information, read: 98http://www2.lm-sensors.nu/~lm78/cvs/lm_sensors2/README.thinkpad 99