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 6 Series (PCH)
20 * Intel Patsburg (PCH)
21 * Intel DH89xxCC (PCH)
22 * Intel Panther Point (PCH)
23 * Intel Lynx Point (PCH)
24 * Intel Lynx Point-LP (PCH)
26 * Intel Wellsburg (PCH)
27 * Intel Coleto Creek (PCH)
28 Datasheets: Publicly available at the Intel website
30 On Intel Patsburg and later chipsets, both the normal host SMBus controller
31 and the additional 'Integrated Device Function' controllers are supported.
34 Mark Studebaker <mdsxyz123@yahoo.com>
35 Jean Delvare <khali@linux-fr.org>
41 * disable_features (bit vector)
42 Disable selected features normally supported by the device. This makes it
43 possible to work around possible driver or hardware bugs if the feature in
44 question doesn't work as intended for whatever reason. Bit values:
46 2 disable the block buffer
47 8 disable the I2C block read functionality
53 The ICH (properly known as the 82801AA), ICH0 (82801AB), ICH2 (82801BA),
54 ICH3 (82801CA/CAM) and later devices (PCH) are Intel chips that are a part of
55 Intel's '810' chipset for Celeron-based PCs, '810E' chipset for
56 Pentium-based PCs, '815E' chipset, and others.
58 The ICH chips contain at least SEVEN separate PCI functions in TWO logical
59 PCI devices. An output of lspci will show something similar to the
62 00:1e.0 PCI bridge: Intel Corporation: Unknown device 2418 (rev 01)
63 00:1f.0 ISA bridge: Intel Corporation: Unknown device 2410 (rev 01)
64 00:1f.1 IDE interface: Intel Corporation: Unknown device 2411 (rev 01)
65 00:1f.2 USB Controller: Intel Corporation: Unknown device 2412 (rev 01)
66 00:1f.3 Unknown class [0c05]: Intel Corporation: Unknown device 2413 (rev 01)
68 The SMBus controller is function 3 in device 1f. Class 0c05 is SMBus Serial
71 The ICH chips are quite similar to Intel's PIIX4 chip, at least in the
81 I2C Block Read Support
82 ----------------------
84 I2C block read is supported on the 82801EB (ICH5) and later chips.
90 The 82801DB (ICH4) and later chips support several SMBus 2.0 features.
96 If your system has an Intel ICH south bridge, but you do NOT see the
97 SMBus device at 00:1f.3 in lspci, and you can't figure out any way in the
98 BIOS to enable it, it means it has been hidden by the BIOS code. Asus is
99 well known for first doing this on their P4B motherboard, and many other
100 boards after that. Some vendor machines are affected as well.
102 The first thing to try is the "i2c_ec" ACPI driver. It could be that the
103 SMBus was hidden on purpose because it'll be driven by ACPI. If the
104 i2c_ec driver works for you, just forget about the i2c-i801 driver and
105 don't try to unhide the ICH SMBus. Even if i2c_ec doesn't work, you
106 better make sure that the SMBus isn't used by the ACPI code. Try loading
107 the "fan" and "thermal" drivers, and check in /proc/acpi/fan and
108 /proc/acpi/thermal_zone. If you find anything there, it's likely that
109 the ACPI is accessing the SMBus and it's safer not to unhide it. Only
110 once you are certain that ACPI isn't using the SMBus, you can attempt
113 In order to unhide the SMBus, we need to change the value of a PCI
114 register before the kernel enumerates the PCI devices. This is done in
115 drivers/pci/quirks.c, where all affected boards must be listed (see
116 function asus_hides_smbus_hostbridge.) If the SMBus device is missing,
117 and you think there's something interesting on the SMBus (e.g. a
118 hardware monitoring chip), you need to add your board to the list.
120 The motherboard is identified using the subvendor and subdevice IDs of the
121 host bridge PCI device. Get yours with "lspci -n -v -s 00:00.0":
123 00:00.0 Class 0600: 8086:2570 (rev 02)
125 Flags: bus master, fast devsel, latency 0
126 Memory at fc000000 (32-bit, prefetchable) [size=32M]
127 Capabilities: [e4] #09 [2106]
128 Capabilities: [a0] AGP version 3.0
130 Here the host bridge ID is 2570 (82865G/PE/P), the subvendor ID is 1043
131 (Asus) and the subdevice ID is 80f2 (P4P800-X). You can find the symbolic
132 names for the bridge ID and the subvendor ID in include/linux/pci_ids.h,
133 and then add a case for your subdevice ID at the right place in
134 drivers/pci/quirks.c. Then please give it very good testing, to make sure
135 that the unhidden SMBus doesn't conflict with e.g. ACPI.
137 If it works, proves useful (i.e. there are usable chips on the SMBus)
138 and seems safe, please submit a patch for inclusion into the kernel.
140 Note: There's a useful script in lm_sensors 2.10.2 and later, named
141 unhide_ICH_SMBus (in prog/hotplug), which uses the fakephp driver to
142 temporarily unhide the SMBus without having to patch and recompile your
143 kernel. It's very convenient if you just want to check if there's
144 anything interesting on your hidden ICH SMBus.
147 **********************
148 The lm_sensors project gratefully acknowledges the support of Texas
149 Instruments in the initial development of this driver.
151 The lm_sensors project gratefully acknowledges the support of Intel in the
152 development of SMBus 2.0 / ICH4 features of this driver.