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1=======================2Kernel driver i2c-piix43=======================4 5Supported adapters:6 * Intel 82371AB PIIX4 and PIIX4E7 * Intel 82443MX (440MX)8 Datasheet: Publicly available at the Intel website9 * ServerWorks OSB4, CSB5, CSB6, HT-1000 and HT-1100 southbridges10 Datasheet: Only available via NDA from ServerWorks11 * ATI IXP200, IXP300, IXP400, SB600, SB700 and SB800 southbridges12 Datasheet: Not publicly available13 SB700 register reference available at:14 http://support.amd.com/us/Embedded_TechDocs/43009_sb7xx_rrg_pub_1.00.pdf15 * AMD SP5100 (SB700 derivative found on some server mainboards)16 Datasheet: Publicly available at the AMD website17 http://support.amd.com/us/Embedded_TechDocs/44413.pdf18 * AMD Hudson-2, ML, CZ19 Datasheet: Not publicly available20 * Hygon CZ21 Datasheet: Not publicly available22 * Standard Microsystems (SMSC) SLC90E66 (Victory66) southbridge23 Datasheet: Publicly available at the SMSC website http://www.smsc.com24 25Authors:26 - Frodo Looijaard <frodol@dds.nl>27 - Philip Edelbrock <phil@netroedge.com>28 29 30Module Parameters31-----------------32 33* force: int34 Forcibly enable the PIIX4. DANGEROUS!35* force_addr: int36 Forcibly enable the PIIX4 at the given address. EXTREMELY DANGEROUS!37 38 39Description40-----------41 42The PIIX4 (properly known as the 82371AB) is an Intel chip with a lot of43functionality. Among other things, it implements the PCI bus. One of its44minor functions is implementing a System Management Bus. This is a true45SMBus - you can not access it on I2C levels. The good news is that it46natively understands SMBus commands and you do not have to worry about47timing problems. The bad news is that non-SMBus devices connected to it can48confuse it mightily. Yes, this is known to happen...49 50Do ``lspci -v`` and see whether it contains an entry like this::51 52 0000:00:02.3 Bridge: Intel Corp. 82371AB/EB/MB PIIX4 ACPI (rev 02)53 Flags: medium devsel, IRQ 954 55Bus and device numbers may differ, but the function number must be56identical (like many PCI devices, the PIIX4 incorporates a number of57different 'functions', which can be considered as separate devices). If you58find such an entry, you have a PIIX4 SMBus controller.59 60On some computers (most notably, some Dells), the SMBus is disabled by61default. If you use the insmod parameter 'force=1', the kernel module will62try to enable it. THIS IS VERY DANGEROUS! If the BIOS did not set up a63correct address for this module, you could get in big trouble (read:64crashes, data corruption, etc.). Try this only as a last resort (try BIOS65updates first, for example), and backup first! An even more dangerous66option is 'force_addr=<IOPORT>'. This will not only enable the PIIX4 like67'force' does, but it will also set a new base I/O port address. The SMBus68parts of the PIIX4 needs a range of 8 of these addresses to function69correctly. If these addresses are already reserved by some other device,70you will get into big trouble! DON'T USE THIS IF YOU ARE NOT VERY SURE71ABOUT WHAT YOU ARE DOING!72 73The PIIX4E is just an new version of the PIIX4; it is supported as well.74The PIIX/PIIX3 does not implement an SMBus or I2C bus, so you can't use75this driver on those mainboards.76 77The ServerWorks Southbridges, the Intel 440MX, and the Victory66 are78identical to the PIIX4 in I2C/SMBus support.79 80The AMD SB700, SB800, SP5100 and Hudson-2 chipsets implement two81PIIX4-compatible SMBus controllers. If your BIOS initializes the82secondary controller, it will be detected by this driver as83an "Auxiliary SMBus Host Controller".84 85If you own Force CPCI735 motherboard or other OSB4 based systems you may need86to change the SMBus Interrupt Select register so the SMBus controller uses87the SMI mode.88 891) Use ``lspci`` command and locate the PCI device with the SMBus controller:90 00:0f.0 ISA bridge: ServerWorks OSB4 South Bridge (rev 4f)91 The line may vary for different chipsets. Please consult the driver source92 for all possible PCI ids (and ``lspci -n`` to match them). Let's assume the93 device is located at 00:0f.0.942) Now you just need to change the value in 0xD2 register. Get it first with95 command: ``lspci -xxx -s 00:0f.0``96 If the value is 0x3 then you need to change it to 0x1:97 ``setpci -s 00:0f.0 d2.b=1``98 99Please note that you don't need to do that in all cases, just when the SMBus is100not working properly.101 102 103Hardware-specific issues104------------------------105 106This driver will refuse to load on IBM systems with an Intel PIIX4 SMBus.107Some of these machines have an RFID EEPROM (24RF08) connected to the SMBus,108which can easily get corrupted due to a state machine bug. These are mostly109Thinkpad laptops, but desktop systems may also be affected. We have no list110of all affected systems, so the only safe solution was to prevent access to111the SMBus on all IBM systems (detected using DMI data.)112