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  * Intel Panther Point (PCH)
23   Datasheets: Publicly available at the Intel website
24
25On Intel Patsburg and later chipsets, both the normal host SMBus controller
26and the additional 'Integrated Device Function' controllers are supported.
27
28Authors:
29	Mark Studebaker <mdsxyz123@yahoo.com>
30	Jean Delvare <khali@linux-fr.org>
31
32
33Module Parameters
34-----------------
35
36* disable_features (bit vector)
37Disable selected features normally supported by the device. This makes it
38possible to work around possible driver or hardware bugs if the feature in
39question doesn't work as intended for whatever reason. Bit values:
40  1  disable SMBus PEC
41  2  disable the block buffer
42  8  disable the I2C block read functionality
43
44
45Description
46-----------
47
48The ICH (properly known as the 82801AA), ICH0 (82801AB), ICH2 (82801BA),
49ICH3 (82801CA/CAM) and later devices (PCH) are Intel chips that are a part of
50Intel's '810' chipset for Celeron-based PCs, '810E' chipset for
51Pentium-based PCs, '815E' chipset, and others.
52
53The ICH chips contain at least SEVEN separate PCI functions in TWO logical
54PCI devices. An output of lspci will show something similar to the
55following:
56
57  00:1e.0 PCI bridge: Intel Corporation: Unknown device 2418 (rev 01)
58  00:1f.0 ISA bridge: Intel Corporation: Unknown device 2410 (rev 01)
59  00:1f.1 IDE interface: Intel Corporation: Unknown device 2411 (rev 01)
60  00:1f.2 USB Controller: Intel Corporation: Unknown device 2412 (rev 01)
61  00:1f.3 Unknown class [0c05]: Intel Corporation: Unknown device 2413 (rev 01)
62
63The SMBus controller is function 3 in device 1f. Class 0c05 is SMBus Serial
64Controller.
65
66The ICH chips are quite similar to Intel's PIIX4 chip, at least in the
67SMBus controller.
68
69
70Process Call Support
71--------------------
72
73Not supported.
74
75
76I2C Block Read Support
77----------------------
78
79I2C block read is supported on the 82801EB (ICH5) and later chips.
80
81
82SMBus 2.0 Support
83-----------------
84
85The 82801DB (ICH4) and later chips support several SMBus 2.0 features.
86
87
88Hidden ICH SMBus
89----------------
90
91If your system has an Intel ICH south bridge, but you do NOT see the
92SMBus device at 00:1f.3 in lspci, and you can't figure out any way in the
93BIOS to enable it, it means it has been hidden by the BIOS code. Asus is
94well known for first doing this on their P4B motherboard, and many other
95boards after that. Some vendor machines are affected as well.
96
97The first thing to try is the "i2c_ec" ACPI driver. It could be that the
98SMBus was hidden on purpose because it'll be driven by ACPI. If the
99i2c_ec driver works for you, just forget about the i2c-i801 driver and
100don't try to unhide the ICH SMBus. Even if i2c_ec doesn't work, you
101better make sure that the SMBus isn't used by the ACPI code. Try loading
102the "fan" and "thermal" drivers, and check in /proc/acpi/fan and
103/proc/acpi/thermal_zone. If you find anything there, it's likely that
104the ACPI is accessing the SMBus and it's safer not to unhide it. Only
105once you are certain that ACPI isn't using the SMBus, you can attempt
106to unhide it.
107
108In order to unhide the SMBus, we need to change the value of a PCI
109register before the kernel enumerates the PCI devices. This is done in
110drivers/pci/quirks.c, where all affected boards must be listed (see
111function asus_hides_smbus_hostbridge.) If the SMBus device is missing,
112and you think there's something interesting on the SMBus (e.g. a
113hardware monitoring chip), you need to add your board to the list.
114
115The motherboard is identified using the subvendor and subdevice IDs of the
116host bridge PCI device. Get yours with "lspci -n -v -s 00:00.0":
117
11800:00.0 Class 0600: 8086:2570 (rev 02)
119        Subsystem: 1043:80f2
120        Flags: bus master, fast devsel, latency 0
121        Memory at fc000000 (32-bit, prefetchable) [size=32M]
122        Capabilities: [e4] #09 [2106]
123        Capabilities: [a0] AGP version 3.0
124
125Here the host bridge ID is 2570 (82865G/PE/P), the subvendor ID is 1043
126(Asus) and the subdevice ID is 80f2 (P4P800-X). You can find the symbolic
127names for the bridge ID and the subvendor ID in include/linux/pci_ids.h,
128and then add a case for your subdevice ID at the right place in
129drivers/pci/quirks.c. Then please give it very good testing, to make sure
130that the unhidden SMBus doesn't conflict with e.g. ACPI.
131
132If it works, proves useful (i.e. there are usable chips on the SMBus)
133and seems safe, please submit a patch for inclusion into the kernel.
134
135Note: There's a useful script in lm_sensors 2.10.2 and later, named
136unhide_ICH_SMBus (in prog/hotplug), which uses the fakephp driver to
137temporarily unhide the SMBus without having to patch and recompile your
138kernel. It's very convenient if you just want to check if there's
139anything interesting on your hidden ICH SMBus.
140
141
142**********************
143The lm_sensors project gratefully acknowledges the support of Texas
144Instruments in the initial development of this driver.
145
146The lm_sensors project gratefully acknowledges the support of Intel in the
147development of SMBus 2.0 / ICH4 features of this driver.
148