i2c-piix4.rst 4.8 KB

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  1. =======================
  2. Kernel driver i2c-piix4
  3. =======================
  4. Supported adapters:
  5. * Intel 82371AB PIIX4 and PIIX4E
  6. * Intel 82443MX (440MX)
  7. Datasheet: Publicly available at the Intel website
  8. * ServerWorks OSB4, CSB5, CSB6, HT-1000 and HT-1100 southbridges
  9. Datasheet: Only available via NDA from ServerWorks
  10. * ATI IXP200, IXP300, IXP400, SB600, SB700 and SB800 southbridges
  11. Datasheet: Not publicly available
  12. SB700 register reference available at:
  13. http://support.amd.com/us/Embedded_TechDocs/43009_sb7xx_rrg_pub_1.00.pdf
  14. * AMD SP5100 (SB700 derivative found on some server mainboards)
  15. Datasheet: Publicly available at the AMD website
  16. http://support.amd.com/us/Embedded_TechDocs/44413.pdf
  17. * AMD Hudson-2, ML, CZ
  18. Datasheet: Not publicly available
  19. * Hygon CZ
  20. Datasheet: Not publicly available
  21. * Standard Microsystems (SMSC) SLC90E66 (Victory66) southbridge
  22. Datasheet: Publicly available at the SMSC website http://www.smsc.com
  23. Authors:
  24. - Frodo Looijaard <frodol@dds.nl>
  25. - Philip Edelbrock <phil@netroedge.com>
  26. Module Parameters
  27. -----------------
  28. * force: int
  29. Forcibly enable the PIIX4. DANGEROUS!
  30. * force_addr: int
  31. Forcibly enable the PIIX4 at the given address. EXTREMELY DANGEROUS!
  32. Description
  33. -----------
  34. The PIIX4 (properly known as the 82371AB) is an Intel chip with a lot of
  35. functionality. Among other things, it implements the PCI bus. One of its
  36. minor functions is implementing a System Management Bus. This is a true
  37. SMBus - you can not access it on I2C levels. The good news is that it
  38. natively understands SMBus commands and you do not have to worry about
  39. timing problems. The bad news is that non-SMBus devices connected to it can
  40. confuse it mightily. Yes, this is known to happen...
  41. Do ``lspci -v`` and see whether it contains an entry like this::
  42. 0000:00:02.3 Bridge: Intel Corp. 82371AB/EB/MB PIIX4 ACPI (rev 02)
  43. Flags: medium devsel, IRQ 9
  44. Bus and device numbers may differ, but the function number must be
  45. identical (like many PCI devices, the PIIX4 incorporates a number of
  46. different 'functions', which can be considered as separate devices). If you
  47. find such an entry, you have a PIIX4 SMBus controller.
  48. On some computers (most notably, some Dells), the SMBus is disabled by
  49. default. If you use the insmod parameter 'force=1', the kernel module will
  50. try to enable it. THIS IS VERY DANGEROUS! If the BIOS did not set up a
  51. correct address for this module, you could get in big trouble (read:
  52. crashes, data corruption, etc.). Try this only as a last resort (try BIOS
  53. updates first, for example), and backup first! An even more dangerous
  54. option is 'force_addr=<IOPORT>'. This will not only enable the PIIX4 like
  55. 'force' foes, but it will also set a new base I/O port address. The SMBus
  56. parts of the PIIX4 needs a range of 8 of these addresses to function
  57. correctly. If these addresses are already reserved by some other device,
  58. you will get into big trouble! DON'T USE THIS IF YOU ARE NOT VERY SURE
  59. ABOUT WHAT YOU ARE DOING!
  60. The PIIX4E is just an new version of the PIIX4; it is supported as well.
  61. The PIIX/PIIX3 does not implement an SMBus or I2C bus, so you can't use
  62. this driver on those mainboards.
  63. The ServerWorks Southbridges, the Intel 440MX, and the Victory66 are
  64. identical to the PIIX4 in I2C/SMBus support.
  65. The AMD SB700, SB800, SP5100 and Hudson-2 chipsets implement two
  66. PIIX4-compatible SMBus controllers. If your BIOS initializes the
  67. secondary controller, it will be detected by this driver as
  68. an "Auxiliary SMBus Host Controller".
  69. If you own Force CPCI735 motherboard or other OSB4 based systems you may need
  70. to change the SMBus Interrupt Select register so the SMBus controller uses
  71. the SMI mode.
  72. 1) Use lspci command and locate the PCI device with the SMBus controller:
  73. 00:0f.0 ISA bridge: ServerWorks OSB4 South Bridge (rev 4f)
  74. The line may vary for different chipsets. Please consult the driver source
  75. for all possible PCI ids (and lspci -n to match them). Lets assume the
  76. device is located at 00:0f.0.
  77. 2) Now you just need to change the value in 0xD2 register. Get it first with
  78. command: lspci -xxx -s 00:0f.0
  79. If the value is 0x3 then you need to change it to 0x1:
  80. setpci -s 00:0f.0 d2.b=1
  81. Please note that you don't need to do that in all cases, just when the SMBus is
  82. not working properly.
  83. Hardware-specific issues
  84. ------------------------
  85. This driver will refuse to load on IBM systems with an Intel PIIX4 SMBus.
  86. Some of these machines have an RFID EEPROM (24RF08) connected to the SMBus,
  87. which can easily get corrupted due to a state machine bug. These are mostly
  88. Thinkpad laptops, but desktop systems may also be affected. We have no list
  89. of all affected systems, so the only safe solution was to prevent access to
  90. the SMBus on all IBM systems (detected using DMI data.)
  91. For additional information, read:
  92. http://www.lm-sensors.org/browser/lm-sensors/trunk/README