1======================
2Kernel driver i2c-i801
3======================
4
5
6Supported adapters:
7  * Intel 82801AA and 82801AB (ICH and ICH0 - part of the
8    '810' and '810E' chipsets)
9  * Intel 82801BA (ICH2 - part of the '815E' chipset)
10  * Intel 82801CA/CAM (ICH3)
11  * Intel 82801DB (ICH4) (HW PEC supported)
12  * Intel 82801EB/ER (ICH5) (HW PEC supported)
13  * Intel 6300ESB
14  * Intel 82801FB/FR/FW/FRW (ICH6)
15  * Intel 82801G (ICH7)
16  * Intel 631xESB/632xESB (ESB2)
17  * Intel 82801H (ICH8)
18  * Intel 82801I (ICH9)
19  * Intel EP80579 (Tolapai)
20  * Intel 82801JI (ICH10)
21  * Intel 5/3400 Series (PCH)
22  * Intel 6 Series (PCH)
23  * Intel Patsburg (PCH)
24  * Intel DH89xxCC (PCH)
25  * Intel Panther Point (PCH)
26  * Intel Lynx Point (PCH)
27  * Intel Avoton (SOC)
28  * Intel Wellsburg (PCH)
29  * Intel Coleto Creek (PCH)
30  * Intel Wildcat Point (PCH)
31  * Intel BayTrail (SOC)
32  * Intel Braswell (SOC)
33  * Intel Sunrise Point (PCH)
34  * Intel Kaby Lake (PCH)
35  * Intel DNV (SOC)
36  * Intel Broxton (SOC)
37  * Intel Lewisburg (PCH)
38  * Intel Gemini Lake (SOC)
39  * Intel Cannon Lake (PCH)
40  * Intel Cedar Fork (PCH)
41  * Intel Ice Lake (PCH)
42  * Intel Comet Lake (PCH)
43  * Intel Elkhart Lake (PCH)
44  * Intel Tiger Lake (PCH)
45  * Intel Jasper Lake (SOC)
46  * Intel Emmitsburg (PCH)
47  * Intel Alder Lake (PCH)
48  * Intel Raptor Lake (PCH)
49  * Intel Meteor Lake (SOC)
50
51   Datasheets: Publicly available at the Intel website
52
53On Intel Patsburg and later chipsets, both the normal host SMBus controller
54and the additional 'Integrated Device Function' controllers are supported.
55
56Authors:
57	- Mark Studebaker <mdsxyz123@yahoo.com>
58	- Jean Delvare <jdelvare@suse.de>
59
60
61Module Parameters
62-----------------
63
64* disable_features (bit vector)
65
66Disable selected features normally supported by the device. This makes it
67possible to work around possible driver or hardware bugs if the feature in
68question doesn't work as intended for whatever reason. Bit values:
69
70 ====  =========================================
71 0x01  disable SMBus PEC
72 0x02  disable the block buffer
73 0x08  disable the I2C block read functionality
74 0x10  don't use interrupts
75 0x20  disable SMBus Host Notify
76 ====  =========================================
77
78
79Description
80-----------
81
82The ICH (properly known as the 82801AA), ICH0 (82801AB), ICH2 (82801BA),
83ICH3 (82801CA/CAM) and later devices (PCH) are Intel chips that are a part of
84Intel's '810' chipset for Celeron-based PCs, '810E' chipset for
85Pentium-based PCs, '815E' chipset, and others.
86
87The ICH chips contain at least SEVEN separate PCI functions in TWO logical
88PCI devices. An output of lspci will show something similar to the
89following::
90
91  00:1e.0 PCI bridge: Intel Corporation: Unknown device 2418 (rev 01)
92  00:1f.0 ISA bridge: Intel Corporation: Unknown device 2410 (rev 01)
93  00:1f.1 IDE interface: Intel Corporation: Unknown device 2411 (rev 01)
94  00:1f.2 USB Controller: Intel Corporation: Unknown device 2412 (rev 01)
95  00:1f.3 Unknown class [0c05]: Intel Corporation: Unknown device 2413 (rev 01)
96
97The SMBus controller is function 3 in device 1f. Class 0c05 is SMBus Serial
98Controller.
99
100The ICH chips are quite similar to Intel's PIIX4 chip, at least in the
101SMBus controller.
102
103
104Process Call Support
105--------------------
106
107Block process call is supported on the 82801EB (ICH5) and later chips.
108
109
110I2C Block Read Support
111----------------------
112
113I2C block read is supported on the 82801EB (ICH5) and later chips.
114
115
116SMBus 2.0 Support
117-----------------
118
119The 82801DB (ICH4) and later chips support several SMBus 2.0 features.
120
121
122Interrupt Support
123-----------------
124
125PCI interrupt support is supported on the 82801EB (ICH5) and later chips.
126
127
128Hidden ICH SMBus
129----------------
130
131If your system has an Intel ICH south bridge, but you do NOT see the
132SMBus device at 00:1f.3 in lspci, and you can't figure out any way in the
133BIOS to enable it, it means it has been hidden by the BIOS code. Asus is
134well known for first doing this on their P4B motherboard, and many other
135boards after that. Some vendor machines are affected as well.
136
137The first thing to try is the "i2c-scmi" ACPI driver. It could be that the
138SMBus was hidden on purpose because it'll be driven by ACPI. If the
139i2c-scmi driver works for you, just forget about the i2c-i801 driver and
140don't try to unhide the ICH SMBus. Even if i2c-scmi doesn't work, you
141better make sure that the SMBus isn't used by the ACPI code. Try loading
142the "fan" and "thermal" drivers, and check in /sys/class/thermal. If you
143find a thermal zone with type "acpitz", it's likely that the ACPI is
144accessing the SMBus and it's safer not to unhide it. Only once you are
145certain that ACPI isn't using the SMBus, you can attempt to unhide it.
146
147In order to unhide the SMBus, we need to change the value of a PCI
148register before the kernel enumerates the PCI devices. This is done in
149drivers/pci/quirks.c, where all affected boards must be listed (see
150function asus_hides_smbus_hostbridge.) If the SMBus device is missing,
151and you think there's something interesting on the SMBus (e.g. a
152hardware monitoring chip), you need to add your board to the list.
153
154The motherboard is identified using the subvendor and subdevice IDs of the
155host bridge PCI device. Get yours with ``lspci -n -v -s 00:00.0``::
156
157  00:00.0 Class 0600: 8086:2570 (rev 02)
158          Subsystem: 1043:80f2
159          Flags: bus master, fast devsel, latency 0
160          Memory at fc000000 (32-bit, prefetchable) [size=32M]
161          Capabilities: [e4] #09 [2106]
162          Capabilities: [a0] AGP version 3.0
163
164Here the host bridge ID is 2570 (82865G/PE/P), the subvendor ID is 1043
165(Asus) and the subdevice ID is 80f2 (P4P800-X). You can find the symbolic
166names for the bridge ID and the subvendor ID in include/linux/pci_ids.h,
167and then add a case for your subdevice ID at the right place in
168drivers/pci/quirks.c. Then please give it very good testing, to make sure
169that the unhidden SMBus doesn't conflict with e.g. ACPI.
170
171If it works, proves useful (i.e. there are usable chips on the SMBus)
172and seems safe, please submit a patch for inclusion into the kernel.
173
174Note: There's a useful script in lm_sensors 2.10.2 and later, named
175unhide_ICH_SMBus (in prog/hotplug), which uses the fakephp driver to
176temporarily unhide the SMBus without having to patch and recompile your
177kernel. It's very convenient if you just want to check if there's
178anything interesting on your hidden ICH SMBus.
179
180
181----------------------------------------------------------------------------
182
183The lm_sensors project gratefully acknowledges the support of Texas
184Instruments in the initial development of this driver.
185
186The lm_sensors project gratefully acknowledges the support of Intel in the
187development of SMBus 2.0 / ICH4 features of this driver.
188