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+Kernel driver i2c-piix4
+ * Intel 82371AB PIIX4 and PIIX4E
+ * Intel 82443MX (440MX)
+ Datasheet: Publicly available at the Intel website
+ * ServerWorks OSB4, CSB5, CSB6, HT-1000 and HT-1100 southbridges
+ Datasheet: Only available via NDA from ServerWorks
+ * ATI IXP200, IXP300, IXP400, SB600, SB700 and SB800 southbridges
+ Datasheet: Not publicly available
+ SB700 register reference available at:
+ * AMD SP5100 (SB700 derivative found on some server mainboards)
+ Datasheet: Publicly available at the AMD website
+ * AMD Hudson-2
+ Datasheet: Not publicly available
+ * Standard Microsystems (SMSC) SLC90E66 (Victory66) southbridge
+ Datasheet: Publicly available at the SMSC website http://www.smsc.com
+ Frodo Looijaard <email@example.com>
+ Philip Edelbrock <firstname.lastname@example.org>
+* force: int
+ Forcibly enable the PIIX4. DANGEROUS!
+* force_addr: int
+ Forcibly enable the PIIX4 at the given address. EXTREMELY DANGEROUS!
+The PIIX4 (properly known as the 82371AB) is an Intel chip with a lot of
+functionality. Among other things, it implements the PCI bus. One of its
+minor functions is implementing a System Management Bus. This is a true
+SMBus - you can not access it on I2C levels. The good news is that it
+natively understands SMBus commands and you do not have to worry about
+timing problems. The bad news is that non-SMBus devices connected to it can
+confuse it mightily. Yes, this is known to happen...
+Do 'lspci -v' and see whether it contains an entry like this:
+0000:00:02.3 Bridge: Intel Corp. 82371AB/EB/MB PIIX4 ACPI (rev 02)
+ Flags: medium devsel, IRQ 9
+Bus and device numbers may differ, but the function number must be
+identical (like many PCI devices, the PIIX4 incorporates a number of
+different 'functions', which can be considered as separate devices). If you
+find such an entry, you have a PIIX4 SMBus controller.
+On some computers (most notably, some Dells), the SMBus is disabled by
+default. If you use the insmod parameter 'force=1', the kernel module will
+try to enable it. THIS IS VERY DANGEROUS! If the BIOS did not set up a
+correct address for this module, you could get in big trouble (read:
+crashes, data corruption, etc.). Try this only as a last resort (try BIOS
+updates first, for example), and backup first! An even more dangerous
+option is 'force_addr=<IOPORT>'. This will not only enable the PIIX4 like
+'force' foes, but it will also set a new base I/O port address. The SMBus
+parts of the PIIX4 needs a range of 8 of these addresses to function
+correctly. If these addresses are already reserved by some other device,
+you will get into big trouble! DON'T USE THIS IF YOU ARE NOT VERY SURE
+ABOUT WHAT YOU ARE DOING!
+The PIIX4E is just an new version of the PIIX4; it is supported as well.
+The PIIX/PIIX3 does not implement an SMBus or I2C bus, so you can't use
+this driver on those mainboards.
+The ServerWorks Southbridges, the Intel 440MX, and the Victory66 are
+identical to the PIIX4 in I2C/SMBus support.
+The AMD SB700 and SP5100 chipsets implement two PIIX4-compatible SMBus
+controllers. If your BIOS initializes the secondary controller, it will
+be detected by this driver as an "Auxiliary SMBus Host Controller".
+If you own Force CPCI735 motherboard or other OSB4 based systems you may need
+to change the SMBus Interrupt Select register so the SMBus controller uses
+the SMI mode.
+1) Use lspci command and locate the PCI device with the SMBus controller:
+ 00:0f.0 ISA bridge: ServerWorks OSB4 South Bridge (rev 4f)
+ The line may vary for different chipsets. Please consult the driver source
+ for all possible PCI ids (and lspci -n to match them). Lets assume the
+ device is located at 00:0f.0.
+2) Now you just need to change the value in 0xD2 register. Get it first with
+ command: lspci -xxx -s 00:0f.0
+ If the value is 0x3 then you need to change it to 0x1
+ setpci -s 00:0f.0 d2.b=1
+Please note that you don't need to do that in all cases, just when the SMBus is
+not working properly.
+This driver will refuse to load on IBM systems with an Intel PIIX4 SMBus.
+Some of these machines have an RFID EEPROM (24RF08) connected to the SMBus,
+which can easily get corrupted due to a state machine bug. These are mostly
+Thinkpad laptops, but desktop systems may also be affected. We have no list
+of all affected systems, so the only safe solution was to prevent access to
+the SMBus on all IBM systems (detected using DMI data.)
+For additional information, read: