4 * Intel 82801AA and 82801AB (ICH and ICH0 - part of the
5 '810' and '810E' chipsets)
6 * Intel 82801BA (ICH2 - part of the '815E' chipset)
7 * Intel 82801CA/CAM (ICH3)
8 * Intel 82801DB (ICH4) (HW PEC supported)
9 * Intel 82801EB/ER (ICH5) (HW PEC supported)
11 * Intel 82801FB/FR/FW/FRW (ICH6)
13 * Intel 631xESB/632xESB (ESB2)
16 * Intel EP80579 (Tolapai)
17 * Intel 82801JI (ICH10)
18 * Intel 5/3400 Series (PCH)
19 * Intel Cougar Point (PCH)
20 * Intel Patsburg (PCH)
21 Datasheets: Publicly available at the Intel website
23 On Intel Patsburg and later chipsets, both the normal host SMBus controller
24 and the additional 'Integrated Device Function' controllers are supported.
27 Mark Studebaker <mdsxyz123@yahoo.com>
28 Jean Delvare <khali@linux-fr.org>
34 * disable_features (bit vector)
35 Disable selected features normally supported by the device. This makes it
36 possible to work around possible driver or hardware bugs if the feature in
37 question doesn't work as intended for whatever reason. Bit values:
39 2 disable the block buffer
40 8 disable the I2C block read functionality
46 The ICH (properly known as the 82801AA), ICH0 (82801AB), ICH2 (82801BA),
47 ICH3 (82801CA/CAM) and later devices (PCH) are Intel chips that are a part of
48 Intel's '810' chipset for Celeron-based PCs, '810E' chipset for
49 Pentium-based PCs, '815E' chipset, and others.
51 The ICH chips contain at least SEVEN separate PCI functions in TWO logical
52 PCI devices. An output of lspci will show something similar to the
55 00:1e.0 PCI bridge: Intel Corporation: Unknown device 2418 (rev 01)
56 00:1f.0 ISA bridge: Intel Corporation: Unknown device 2410 (rev 01)
57 00:1f.1 IDE interface: Intel Corporation: Unknown device 2411 (rev 01)
58 00:1f.2 USB Controller: Intel Corporation: Unknown device 2412 (rev 01)
59 00:1f.3 Unknown class [0c05]: Intel Corporation: Unknown device 2413 (rev 01)
61 The SMBus controller is function 3 in device 1f. Class 0c05 is SMBus Serial
64 The ICH chips are quite similar to Intel's PIIX4 chip, at least in the
74 I2C Block Read Support
75 ----------------------
77 I2C block read is supported on the 82801EB (ICH5) and later chips.
83 The 82801DB (ICH4) and later chips support several SMBus 2.0 features.
89 If your system has an Intel ICH south bridge, but you do NOT see the
90 SMBus device at 00:1f.3 in lspci, and you can't figure out any way in the
91 BIOS to enable it, it means it has been hidden by the BIOS code. Asus is
92 well known for first doing this on their P4B motherboard, and many other
93 boards after that. Some vendor machines are affected as well.
95 The first thing to try is the "i2c_ec" ACPI driver. It could be that the
96 SMBus was hidden on purpose because it'll be driven by ACPI. If the
97 i2c_ec driver works for you, just forget about the i2c-i801 driver and
98 don't try to unhide the ICH SMBus. Even if i2c_ec doesn't work, you
99 better make sure that the SMBus isn't used by the ACPI code. Try loading
100 the "fan" and "thermal" drivers, and check in /proc/acpi/fan and
101 /proc/acpi/thermal_zone. If you find anything there, it's likely that
102 the ACPI is accessing the SMBus and it's safer not to unhide it. Only
103 once you are certain that ACPI isn't using the SMBus, you can attempt
106 In order to unhide the SMBus, we need to change the value of a PCI
107 register before the kernel enumerates the PCI devices. This is done in
108 drivers/pci/quirks.c, where all affected boards must be listed (see
109 function asus_hides_smbus_hostbridge.) If the SMBus device is missing,
110 and you think there's something interesting on the SMBus (e.g. a
111 hardware monitoring chip), you need to add your board to the list.
113 The motherboard is identified using the subvendor and subdevice IDs of the
114 host bridge PCI device. Get yours with "lspci -n -v -s 00:00.0":
116 00:00.0 Class 0600: 8086:2570 (rev 02)
118 Flags: bus master, fast devsel, latency 0
119 Memory at fc000000 (32-bit, prefetchable) [size=32M]
120 Capabilities: [e4] #09 [2106]
121 Capabilities: [a0] AGP version 3.0
123 Here the host bridge ID is 2570 (82865G/PE/P), the subvendor ID is 1043
124 (Asus) and the subdevice ID is 80f2 (P4P800-X). You can find the symbolic
125 names for the bridge ID and the subvendor ID in include/linux/pci_ids.h,
126 and then add a case for your subdevice ID at the right place in
127 drivers/pci/quirks.c. Then please give it very good testing, to make sure
128 that the unhidden SMBus doesn't conflict with e.g. ACPI.
130 If it works, proves useful (i.e. there are usable chips on the SMBus)
131 and seems safe, please submit a patch for inclusion into the kernel.
133 Note: There's a useful script in lm_sensors 2.10.2 and later, named
134 unhide_ICH_SMBus (in prog/hotplug), which uses the fakephp driver to
135 temporarily unhide the SMBus without having to patch and recompile your
136 kernel. It's very convenient if you just want to check if there's
137 anything interesting on your hidden ICH SMBus.
140 **********************
141 The lm_sensors project gratefully acknowledges the support of Texas
142 Instruments in the initial development of this driver.
144 The lm_sensors project gratefully acknowledges the support of Intel in the
145 development of SMBus 2.0 / ICH4 features of this driver.