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1Kernel driver i2c-i801
2
3Supported adapters:
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)
10 * Intel 6300ESB
11 * Intel 82801FB/FR/FW/FRW (ICH6)
12 * Intel 82801G (ICH7)
13 * Intel 631xESB/632xESB (ESB2)
14 * Intel 82801H (ICH8)
15 * Intel 82801I (ICH9)
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 Datasheets: Publicly available at the Intel website
23
24On Intel Patsburg and later chipsets, both the normal host SMBus controller
25and the additional 'Integrated Device Function' controllers are supported.
26
27Authors:
28 Mark Studebaker <mdsxyz123@yahoo.com>
29 Jean Delvare <khali@linux-fr.org>
30
31
32Module Parameters
33-----------------
34
35* disable_features (bit vector)
36Disable selected features normally supported by the device. This makes it
37possible to work around possible driver or hardware bugs if the feature in
38question doesn't work as intended for whatever reason. Bit values:
39 1 disable SMBus PEC
40 2 disable the block buffer
41 8 disable the I2C block read functionality
42
43
44Description
45-----------
46
47The ICH (properly known as the 82801AA), ICH0 (82801AB), ICH2 (82801BA),
48ICH3 (82801CA/CAM) and later devices (PCH) are Intel chips that are a part of
49Intel's '810' chipset for Celeron-based PCs, '810E' chipset for
50Pentium-based PCs, '815E' chipset, and others.
51
52The ICH chips contain at least SEVEN separate PCI functions in TWO logical
53PCI devices. An output of lspci will show something similar to the
54following:
55
56 00:1e.0 PCI bridge: Intel Corporation: Unknown device 2418 (rev 01)
57 00:1f.0 ISA bridge: Intel Corporation: Unknown device 2410 (rev 01)
58 00:1f.1 IDE interface: Intel Corporation: Unknown device 2411 (rev 01)
59 00:1f.2 USB Controller: Intel Corporation: Unknown device 2412 (rev 01)
60 00:1f.3 Unknown class [0c05]: Intel Corporation: Unknown device 2413 (rev 01)
61
62The SMBus controller is function 3 in device 1f. Class 0c05 is SMBus Serial
63Controller.
64
65The ICH chips are quite similar to Intel's PIIX4 chip, at least in the
66SMBus controller.
67
68
69Process Call Support
70--------------------
71
72Not supported.
73
74
75I2C Block Read Support
76----------------------
77
78I2C block read is supported on the 82801EB (ICH5) and later chips.
79
80
81SMBus 2.0 Support
82-----------------
83
84The 82801DB (ICH4) and later chips support several SMBus 2.0 features.
85
86
87Hidden ICH SMBus
88----------------
89
90If your system has an Intel ICH south bridge, but you do NOT see the
91SMBus device at 00:1f.3 in lspci, and you can't figure out any way in the
92BIOS to enable it, it means it has been hidden by the BIOS code. Asus is
93well known for first doing this on their P4B motherboard, and many other
94boards after that. Some vendor machines are affected as well.
95
96The first thing to try is the "i2c_ec" ACPI driver. It could be that the
97SMBus was hidden on purpose because it'll be driven by ACPI. If the
98i2c_ec driver works for you, just forget about the i2c-i801 driver and
99don't try to unhide the ICH SMBus. Even if i2c_ec doesn't work, you
100better make sure that the SMBus isn't used by the ACPI code. Try loading
101the "fan" and "thermal" drivers, and check in /proc/acpi/fan and
102/proc/acpi/thermal_zone. If you find anything there, it's likely that
103the ACPI is accessing the SMBus and it's safer not to unhide it. Only
104once you are certain that ACPI isn't using the SMBus, you can attempt
105to unhide it.
106
107In order to unhide the SMBus, we need to change the value of a PCI
108register before the kernel enumerates the PCI devices. This is done in
109drivers/pci/quirks.c, where all affected boards must be listed (see
110function asus_hides_smbus_hostbridge.) If the SMBus device is missing,
111and you think there's something interesting on the SMBus (e.g. a
112hardware monitoring chip), you need to add your board to the list.
113
114The motherboard is identified using the subvendor and subdevice IDs of the
115host bridge PCI device. Get yours with "lspci -n -v -s 00:00.0":
116
11700:00.0 Class 0600: 8086:2570 (rev 02)
118 Subsystem: 1043:80f2
119 Flags: bus master, fast devsel, latency 0
120 Memory at fc000000 (32-bit, prefetchable) [size=32M]
121 Capabilities: [e4] #09 [2106]
122 Capabilities: [a0] AGP version 3.0
123
124Here the host bridge ID is 2570 (82865G/PE/P), the subvendor ID is 1043
125(Asus) and the subdevice ID is 80f2 (P4P800-X). You can find the symbolic
126names for the bridge ID and the subvendor ID in include/linux/pci_ids.h,
127and then add a case for your subdevice ID at the right place in
128drivers/pci/quirks.c. Then please give it very good testing, to make sure
129that the unhidden SMBus doesn't conflict with e.g. ACPI.
130
131If it works, proves useful (i.e. there are usable chips on the SMBus)
132and seems safe, please submit a patch for inclusion into the kernel.
133
134Note: There's a useful script in lm_sensors 2.10.2 and later, named
135unhide_ICH_SMBus (in prog/hotplug), which uses the fakephp driver to
136temporarily unhide the SMBus without having to patch and recompile your
137kernel. It's very convenient if you just want to check if there's
138anything interesting on your hidden ICH SMBus.
139
140
141**********************
142The lm_sensors project gratefully acknowledges the support of Texas
143Instruments in the initial development of this driver.
144
145The lm_sensors project gratefully acknowledges the support of Intel in the
146development of SMBus 2.0 / ICH4 features of this driver.