0001 =======================
0002 Kernel driver i2c-piix4
0003 =======================
0004
0005 Supported adapters:
0006 * Intel 82371AB PIIX4 and PIIX4E
0007 * Intel 82443MX (440MX)
0008 Datasheet: Publicly available at the Intel website
0009 * ServerWorks OSB4, CSB5, CSB6, HT-1000 and HT-1100 southbridges
0010 Datasheet: Only available via NDA from ServerWorks
0011 * ATI IXP200, IXP300, IXP400, SB600, SB700 and SB800 southbridges
0012 Datasheet: Not publicly available
0013 SB700 register reference available at:
0014 http://support.amd.com/us/Embedded_TechDocs/43009_sb7xx_rrg_pub_1.00.pdf
0015 * AMD SP5100 (SB700 derivative found on some server mainboards)
0016 Datasheet: Publicly available at the AMD website
0017 http://support.amd.com/us/Embedded_TechDocs/44413.pdf
0018 * AMD Hudson-2, ML, CZ
0019 Datasheet: Not publicly available
0020 * Hygon CZ
0021 Datasheet: Not publicly available
0022 * Standard Microsystems (SMSC) SLC90E66 (Victory66) southbridge
0023 Datasheet: Publicly available at the SMSC website http://www.smsc.com
0024
0025 Authors:
0026 - Frodo Looijaard <frodol@dds.nl>
0027 - Philip Edelbrock <phil@netroedge.com>
0028
0029
0030 Module Parameters
0031 -----------------
0032
0033 * force: int
0034 Forcibly enable the PIIX4. DANGEROUS!
0035 * force_addr: int
0036 Forcibly enable the PIIX4 at the given address. EXTREMELY DANGEROUS!
0037
0038
0039 Description
0040 -----------
0041
0042 The PIIX4 (properly known as the 82371AB) is an Intel chip with a lot of
0043 functionality. Among other things, it implements the PCI bus. One of its
0044 minor functions is implementing a System Management Bus. This is a true
0045 SMBus - you can not access it on I2C levels. The good news is that it
0046 natively understands SMBus commands and you do not have to worry about
0047 timing problems. The bad news is that non-SMBus devices connected to it can
0048 confuse it mightily. Yes, this is known to happen...
0049
0050 Do ``lspci -v`` and see whether it contains an entry like this::
0051
0052 0000:00:02.3 Bridge: Intel Corp. 82371AB/EB/MB PIIX4 ACPI (rev 02)
0053 Flags: medium devsel, IRQ 9
0054
0055 Bus and device numbers may differ, but the function number must be
0056 identical (like many PCI devices, the PIIX4 incorporates a number of
0057 different 'functions', which can be considered as separate devices). If you
0058 find such an entry, you have a PIIX4 SMBus controller.
0059
0060 On some computers (most notably, some Dells), the SMBus is disabled by
0061 default. If you use the insmod parameter 'force=1', the kernel module will
0062 try to enable it. THIS IS VERY DANGEROUS! If the BIOS did not set up a
0063 correct address for this module, you could get in big trouble (read:
0064 crashes, data corruption, etc.). Try this only as a last resort (try BIOS
0065 updates first, for example), and backup first! An even more dangerous
0066 option is 'force_addr=<IOPORT>'. This will not only enable the PIIX4 like
0067 'force' does, but it will also set a new base I/O port address. The SMBus
0068 parts of the PIIX4 needs a range of 8 of these addresses to function
0069 correctly. If these addresses are already reserved by some other device,
0070 you will get into big trouble! DON'T USE THIS IF YOU ARE NOT VERY SURE
0071 ABOUT WHAT YOU ARE DOING!
0072
0073 The PIIX4E is just an new version of the PIIX4; it is supported as well.
0074 The PIIX/PIIX3 does not implement an SMBus or I2C bus, so you can't use
0075 this driver on those mainboards.
0076
0077 The ServerWorks Southbridges, the Intel 440MX, and the Victory66 are
0078 identical to the PIIX4 in I2C/SMBus support.
0079
0080 The AMD SB700, SB800, SP5100 and Hudson-2 chipsets implement two
0081 PIIX4-compatible SMBus controllers. If your BIOS initializes the
0082 secondary controller, it will be detected by this driver as
0083 an "Auxiliary SMBus Host Controller".
0084
0085 If you own Force CPCI735 motherboard or other OSB4 based systems you may need
0086 to change the SMBus Interrupt Select register so the SMBus controller uses
0087 the SMI mode.
0088
0089 1) Use ``lspci`` command and locate the PCI device with the SMBus controller:
0090 00:0f.0 ISA bridge: ServerWorks OSB4 South Bridge (rev 4f)
0091 The line may vary for different chipsets. Please consult the driver source
0092 for all possible PCI ids (and ``lspci -n`` to match them). Let's assume the
0093 device is located at 00:0f.0.
0094 2) Now you just need to change the value in 0xD2 register. Get it first with
0095 command: ``lspci -xxx -s 00:0f.0``
0096 If the value is 0x3 then you need to change it to 0x1:
0097 ``setpci -s 00:0f.0 d2.b=1``
0098
0099 Please note that you don't need to do that in all cases, just when the SMBus is
0100 not working properly.
0101
0102
0103 Hardware-specific issues
0104 ------------------------
0105
0106 This driver will refuse to load on IBM systems with an Intel PIIX4 SMBus.
0107 Some of these machines have an RFID EEPROM (24RF08) connected to the SMBus,
0108 which can easily get corrupted due to a state machine bug. These are mostly
0109 Thinkpad laptops, but desktop systems may also be affected. We have no list
0110 of all affected systems, so the only safe solution was to prevent access to
0111 the SMBus on all IBM systems (detected using DMI data.)
