135 lines
4.9 KiB
Plaintext
135 lines
4.9 KiB
Plaintext
Kernel driver i2c-i801
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Supported adapters:
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* Intel 82801AA and 82801AB (ICH and ICH0 - part of the
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'810' and '810E' chipsets)
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* Intel 82801BA (ICH2 - part of the '815E' chipset)
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* Intel 82801CA/CAM (ICH3)
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* Intel 82801DB (ICH4) (HW PEC supported)
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* Intel 82801EB/ER (ICH5) (HW PEC supported)
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* Intel 6300ESB
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* Intel 82801FB/FR/FW/FRW (ICH6)
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* Intel 82801G (ICH7)
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* Intel 631xESB/632xESB (ESB2)
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* Intel 82801H (ICH8)
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* Intel 82801I (ICH9)
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* Intel EP80579 (Tolapai)
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* Intel 82801JI (ICH10)
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* Intel PCH
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Datasheets: Publicly available at the Intel website
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Authors:
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Mark Studebaker <mdsxyz123@yahoo.com>
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Jean Delvare <khali@linux-fr.org>
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Module Parameters
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-----------------
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None.
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Description
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-----------
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The ICH (properly known as the 82801AA), ICH0 (82801AB), ICH2 (82801BA),
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ICH3 (82801CA/CAM) and later devices (PCH) are Intel chips that are a part of
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Intel's '810' chipset for Celeron-based PCs, '810E' chipset for
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Pentium-based PCs, '815E' chipset, and others.
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The ICH chips contain at least SEVEN separate PCI functions in TWO logical
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PCI devices. An output of lspci will show something similar to the
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following:
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00:1e.0 PCI bridge: Intel Corporation: Unknown device 2418 (rev 01)
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00:1f.0 ISA bridge: Intel Corporation: Unknown device 2410 (rev 01)
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00:1f.1 IDE interface: Intel Corporation: Unknown device 2411 (rev 01)
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00:1f.2 USB Controller: Intel Corporation: Unknown device 2412 (rev 01)
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00:1f.3 Unknown class [0c05]: Intel Corporation: Unknown device 2413 (rev 01)
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The SMBus controller is function 3 in device 1f. Class 0c05 is SMBus Serial
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Controller.
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The ICH chips are quite similar to Intel's PIIX4 chip, at least in the
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SMBus controller.
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Process Call Support
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--------------------
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Not supported.
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I2C Block Read Support
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----------------------
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I2C block read is supported on the 82801EB (ICH5) and later chips.
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SMBus 2.0 Support
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-----------------
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The 82801DB (ICH4) and later chips support several SMBus 2.0 features.
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Hidden ICH SMBus
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----------------
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If your system has an Intel ICH south bridge, but you do NOT see the
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SMBus device at 00:1f.3 in lspci, and you can't figure out any way in the
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BIOS to enable it, it means it has been hidden by the BIOS code. Asus is
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well known for first doing this on their P4B motherboard, and many other
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boards after that. Some vendor machines are affected as well.
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The first thing to try is the "i2c_ec" ACPI driver. It could be that the
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SMBus was hidden on purpose because it'll be driven by ACPI. If the
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i2c_ec driver works for you, just forget about the i2c-i801 driver and
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don't try to unhide the ICH SMBus. Even if i2c_ec doesn't work, you
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better make sure that the SMBus isn't used by the ACPI code. Try loading
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the "fan" and "thermal" drivers, and check in /proc/acpi/fan and
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/proc/acpi/thermal_zone. If you find anything there, it's likely that
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the ACPI is accessing the SMBus and it's safer not to unhide it. Only
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once you are certain that ACPI isn't using the SMBus, you can attempt
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to unhide it.
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In order to unhide the SMBus, we need to change the value of a PCI
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register before the kernel enumerates the PCI devices. This is done in
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drivers/pci/quirks.c, where all affected boards must be listed (see
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function asus_hides_smbus_hostbridge.) If the SMBus device is missing,
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and you think there's something interesting on the SMBus (e.g. a
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hardware monitoring chip), you need to add your board to the list.
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The motherboard is identified using the subvendor and subdevice IDs of the
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host bridge PCI device. Get yours with "lspci -n -v -s 00:00.0":
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00:00.0 Class 0600: 8086:2570 (rev 02)
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Subsystem: 1043:80f2
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Flags: bus master, fast devsel, latency 0
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Memory at fc000000 (32-bit, prefetchable) [size=32M]
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Capabilities: [e4] #09 [2106]
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Capabilities: [a0] AGP version 3.0
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Here the host bridge ID is 2570 (82865G/PE/P), the subvendor ID is 1043
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(Asus) and the subdevice ID is 80f2 (P4P800-X). You can find the symbolic
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names for the bridge ID and the subvendor ID in include/linux/pci_ids.h,
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and then add a case for your subdevice ID at the right place in
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drivers/pci/quirks.c. Then please give it very good testing, to make sure
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that the unhidden SMBus doesn't conflict with e.g. ACPI.
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If it works, proves useful (i.e. there are usable chips on the SMBus)
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and seems safe, please submit a patch for inclusion into the kernel.
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Note: There's a useful script in lm_sensors 2.10.2 and later, named
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unhide_ICH_SMBus (in prog/hotplug), which uses the fakephp driver to
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temporarily unhide the SMBus without having to patch and recompile your
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kernel. It's very convenient if you just want to check if there's
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anything interesting on your hidden ICH SMBus.
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**********************
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The lm_sensors project gratefully acknowledges the support of Texas
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Instruments in the initial development of this driver.
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The lm_sensors project gratefully acknowledges the support of Intel in the
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development of SMBus 2.0 / ICH4 features of this driver.
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