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Documentation / i2c / busses / i2c-i801


Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.

1	Kernel driver i2c-i801
2	
3	Supported 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	  * Intel Lynx Point (PCH)
24	  * Intel Lynx Point-LP (PCH)
25	  * Intel Avoton (SOC)
26	  * Intel Wellsburg (PCH)
27	  * Intel Coleto Creek (PCH)
28	  * Intel Wildcat Point (PCH)
29	  * Intel Wildcat Point-LP (PCH)
30	  * Intel BayTrail (SOC)
31	  * Intel Braswell (SOC)
32	  * Intel Sunrise Point-H (PCH)
33	  * Intel Sunrise Point-LP (PCH)
34	  * Intel Kaby Lake-H (PCH)
35	  * Intel DNV (SOC)
36	  * Intel Broxton (SOC)
37	  * Intel Lewisburg (PCH)
38	  * Intel Gemini Lake (SOC)
39	  * Intel Cannon Lake-H (PCH)
40	  * Intel Cannon Lake-LP (PCH)
41	  * Intel Cedar Fork (PCH)
42	   Datasheets: Publicly available at the Intel website
43	
44	On Intel Patsburg and later chipsets, both the normal host SMBus controller
45	and the additional 'Integrated Device Function' controllers are supported.
46	
47	Authors: 
48		Mark Studebaker <mdsxyz123@yahoo.com>
49		Jean Delvare <jdelvare@suse.de>
50	
51	
52	Module Parameters
53	-----------------
54	
55	* disable_features (bit vector)
56	Disable selected features normally supported by the device. This makes it
57	possible to work around possible driver or hardware bugs if the feature in
58	question doesn't work as intended for whatever reason. Bit values:
59	 0x01  disable SMBus PEC
60	 0x02  disable the block buffer
61	 0x08  disable the I2C block read functionality
62	 0x10  don't use interrupts
63	
64	
65	Description
66	-----------
67	
68	The ICH (properly known as the 82801AA), ICH0 (82801AB), ICH2 (82801BA),
69	ICH3 (82801CA/CAM) and later devices (PCH) are Intel chips that are a part of
70	Intel's '810' chipset for Celeron-based PCs, '810E' chipset for
71	Pentium-based PCs, '815E' chipset, and others.
72	
73	The ICH chips contain at least SEVEN separate PCI functions in TWO logical
74	PCI devices. An output of lspci will show something similar to the
75	following:
76	
77	  00:1e.0 PCI bridge: Intel Corporation: Unknown device 2418 (rev 01)
78	  00:1f.0 ISA bridge: Intel Corporation: Unknown device 2410 (rev 01)
79	  00:1f.1 IDE interface: Intel Corporation: Unknown device 2411 (rev 01)
80	  00:1f.2 USB Controller: Intel Corporation: Unknown device 2412 (rev 01)
81	  00:1f.3 Unknown class [0c05]: Intel Corporation: Unknown device 2413 (rev 01)
82	
83	The SMBus controller is function 3 in device 1f. Class 0c05 is SMBus Serial
84	Controller.
85	
86	The ICH chips are quite similar to Intel's PIIX4 chip, at least in the
87	SMBus controller.
88	
89	
90	Process Call Support
91	--------------------
92	
93	Not supported.
94	
95	
96	I2C Block Read Support
97	----------------------
98	
99	I2C block read is supported on the 82801EB (ICH5) and later chips.
100	
101	
102	SMBus 2.0 Support
103	-----------------
104	
105	The 82801DB (ICH4) and later chips support several SMBus 2.0 features.
106	
107	
108	Interrupt Support
109	-----------------
110	
111	PCI interrupt support is supported on the 82801EB (ICH5) and later chips.
112	
113	
114	Hidden ICH SMBus
115	----------------
116	
117	If your system has an Intel ICH south bridge, but you do NOT see the
118	SMBus device at 00:1f.3 in lspci, and you can't figure out any way in the
119	BIOS to enable it, it means it has been hidden by the BIOS code. Asus is
120	well known for first doing this on their P4B motherboard, and many other
121	boards after that. Some vendor machines are affected as well.
122	
123	The first thing to try is the "i2c_ec" ACPI driver. It could be that the
124	SMBus was hidden on purpose because it'll be driven by ACPI. If the
125	i2c_ec driver works for you, just forget about the i2c-i801 driver and
126	don't try to unhide the ICH SMBus. Even if i2c_ec doesn't work, you
127	better make sure that the SMBus isn't used by the ACPI code. Try loading
128	the "fan" and "thermal" drivers, and check in /proc/acpi/fan and
129	/proc/acpi/thermal_zone. If you find anything there, it's likely that
130	the ACPI is accessing the SMBus and it's safer not to unhide it. Only
131	once you are certain that ACPI isn't using the SMBus, you can attempt
132	to unhide it.
133	
134	In order to unhide the SMBus, we need to change the value of a PCI
135	register before the kernel enumerates the PCI devices. This is done in
136	drivers/pci/quirks.c, where all affected boards must be listed (see
137	function asus_hides_smbus_hostbridge.) If the SMBus device is missing,
138	and you think there's something interesting on the SMBus (e.g. a
139	hardware monitoring chip), you need to add your board to the list.
140	
141	The motherboard is identified using the subvendor and subdevice IDs of the
142	host bridge PCI device. Get yours with "lspci -n -v -s 00:00.0":
143	
144	00:00.0 Class 0600: 8086:2570 (rev 02)
145	        Subsystem: 1043:80f2
146	        Flags: bus master, fast devsel, latency 0
147	        Memory at fc000000 (32-bit, prefetchable) [size=32M]
148	        Capabilities: [e4] #09 [2106]
149	        Capabilities: [a0] AGP version 3.0
150	
151	Here the host bridge ID is 2570 (82865G/PE/P), the subvendor ID is 1043
152	(Asus) and the subdevice ID is 80f2 (P4P800-X). You can find the symbolic
153	names for the bridge ID and the subvendor ID in include/linux/pci_ids.h,
154	and then add a case for your subdevice ID at the right place in
155	drivers/pci/quirks.c. Then please give it very good testing, to make sure
156	that the unhidden SMBus doesn't conflict with e.g. ACPI.
157	
158	If it works, proves useful (i.e. there are usable chips on the SMBus)
159	and seems safe, please submit a patch for inclusion into the kernel.
160	
161	Note: There's a useful script in lm_sensors 2.10.2 and later, named
162	unhide_ICH_SMBus (in prog/hotplug), which uses the fakephp driver to
163	temporarily unhide the SMBus without having to patch and recompile your
164	kernel. It's very convenient if you just want to check if there's
165	anything interesting on your hidden ICH SMBus.
166	
167	
168	**********************
169	The lm_sensors project gratefully acknowledges the support of Texas
170	Instruments in the initial development of this driver.
171	
172	The lm_sensors project gratefully acknowledges the support of Intel in the
173	development of SMBus 2.0 / ICH4 features of this driver.
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