| Kernel driver i2c-piix4 | |
| Supported adapters: | |
| * 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 | |
| * AMD Hudson-2 | |
| Datasheet: Not publicly available | |
| * Standard Microsystems (SMSC) SLC90E66 (Victory66) southbridge | |
| Datasheet: Publicly available at the SMSC website http://www.smsc.com | |
| Authors: | |
| Frodo Looijaard <frodol@dds.nl> | |
| Philip Edelbrock <phil@netroedge.com> | |
| Module Parameters | |
| ----------------- | |
| * force: int | |
| Forcibly enable the PIIX4. DANGEROUS! | |
| * force_addr: int | |
| Forcibly enable the PIIX4 at the given address. EXTREMELY DANGEROUS! | |
| Description | |
| ----------- | |
| 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. | |
| 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. | |
| Hardware-specific issues | |
| ------------------------ | |
| 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: | |
| http://www.lm-sensors.org/browser/lm-sensors/trunk/README |