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Based on kernel version 2.6.33. Page generated on 2010-02-24 15:36 EST.

1	Kernel driver lm85
2	==================
3	
4	Supported chips:
5	  * National Semiconductor LM85 (B and C versions)
6	    Prefix: 'lm85'
7	    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
8	    Datasheet: http://www.national.com/pf/LM/LM85.html
9	  * Analog Devices ADM1027
10	    Prefix: 'adm1027'
11	    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
12	    Datasheet: http://www.analog.com/en/prod/0,,766_825_ADM1027,00.html
13	  * Analog Devices ADT7463
14	    Prefix: 'adt7463'
15	    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
16	    Datasheet: http://www.analog.com/en/prod/0,,766_825_ADT7463,00.html
17	  * SMSC EMC6D100, SMSC EMC6D101
18	    Prefix: 'emc6d100'
19	    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
20	    Datasheet: http://www.smsc.com/main/tools/discontinued/6d100.pdf
21	  * SMSC EMC6D102
22	    Prefix: 'emc6d102'
23	    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
24	    Datasheet: http://www.smsc.com/main/catalog/emc6d102.html
25	
26	Authors:
27	        Philip Pokorny <ppokorny[AT]penguincomputing[DOT]com>,
28	        Frodo Looijaard <frodol[AT]dds[DOT]nl>,
29	        Richard Barrington <rich_b_nz[AT]clear.net[DOT]nz>,
30	        Margit Schubert-While <margitsw[AT]t-online[DOT]de>,
31	        Justin Thiessen <jthiessen[AT]penguincomputing[DOT]com>
32	
33	Description
34	-----------
35	
36	This driver implements support for the National Semiconductor LM85 and
37	compatible chips including the Analog Devices ADM1027, ADT7463 and
38	SMSC EMC6D10x chips family.
39	
40	The LM85 uses the 2-wire interface compatible with the SMBUS 2.0
41	specification. Using an analog to digital converter it measures three (3)
42	temperatures and five (5) voltages. It has four (4) 16-bit counters for
43	measuring fan speed. Five (5) digital inputs are provided for sampling the
44	VID signals from the processor to the VRM. Lastly, there are three (3) PWM
45	outputs that can be used to control fan speed.
46	
47	The voltage inputs have internal scaling resistors so that the following
48	voltage can be measured without external resistors:
49	
50	  2.5V, 3.3V, 5V, 12V, and CPU core voltage (2.25V)
51	
52	The temperatures measured are one internal diode, and two remote diodes.
53	Remote 1 is generally the CPU temperature. These inputs are designed to
54	measure a thermal diode like the one in a Pentium 4 processor in a socket
55	423 or socket 478 package. They can also measure temperature using a
56	transistor like the 2N3904.
57	
58	A sophisticated control system for the PWM outputs is designed into the
59	LM85 that allows fan speed to be adjusted automatically based on any of the
60	three temperature sensors. Each PWM output is individually adjustable and
61	programmable. Once configured, the LM85 will adjust the PWM outputs in
62	response to the measured temperatures without further host intervention.
63	This feature can also be disabled for manual control of the PWM's.
64	
65	Each of the measured inputs (voltage, temperature, fan speed) has
66	corresponding high/low limit values. The LM85 will signal an ALARM if any
67	measured value exceeds either limit.
68	
69	The LM85 samples all inputs continuously. The lm85 driver will not read
70	the registers more often than once a second. Further, configuration data is
71	only read once each 5 minutes. There is twice as much config data as
72	measurements, so this would seem to be a worthwhile optimization.
73	
74	Special Features
75	----------------
76	
77	The LM85 has four fan speed monitoring modes. The ADM1027 has only two.
78	Both have special circuitry to compensate for PWM interactions with the
79	TACH signal from the fans. The ADM1027 can be configured to measure the
80	speed of a two wire fan, but the input conditioning circuitry is different
81	for 3-wire and 2-wire mode. For this reason, the 2-wire fan modes are not
82	exposed to user control. The BIOS should initialize them to the correct
83	mode. If you've designed your own ADM1027, you'll have to modify the
84	init_client function and add an insmod parameter to set this up.
85	
86	To smooth the response of fans to changes in temperature, the LM85 has an
87	optional filter for smoothing temperatures. The ADM1027 has the same
88	config option but uses it to rate limit the changes to fan speed instead.
89	
90	The ADM1027 and ADT7463 have a 10-bit ADC and can therefore measure
91	temperatures with 0.25 degC resolution. They also provide an offset to the
92	temperature readings that is automatically applied during measurement.
93	This offset can be used to zero out any errors due to traces and placement.
94	The documentation says that the offset is in 0.25 degC steps, but in
95	initial testing of the ADM1027 it was 1.00 degC steps. Analog Devices has
96	confirmed this "bug". The ADT7463 is reported to work as described in the
97	documentation. The current lm85 driver does not show the offset register.
98	
99	See the vendor datasheets for more information. There is application note
100	from National (AN-1260) with some additional information about the LM85.
101	The Analog Devices datasheet is very detailed and describes a procedure for
102	determining an optimal configuration for the automatic PWM control.
103	
104	The SMSC EMC6D100 & EMC6D101 monitor external voltages, temperatures, and
105	fan speeds. They use this monitoring capability to alert the system to out
106	of limit conditions and can automatically control the speeds of multiple
107	fans in a PC or embedded system. The EMC6D101, available in a 24-pin SSOP
108	package, and the EMC6D100, available in a 28-pin SSOP package, are designed
109	to be register compatible. The EMC6D100 offers all the features of the
110	EMC6D101 plus additional voltage monitoring and system control features.
111	Unfortunately it is not possible to distinguish between the package
112	versions on register level so these additional voltage inputs may read
113	zero. The EMC6D102 features addtional ADC bits thus extending precision
114	of voltage and temperature channels.
115	
116	
117	Hardware Configurations
118	-----------------------
119	
120	The LM85 can be jumpered for 3 different SMBus addresses. There are
121	no other hardware configuration options for the LM85.
122	
123	The lm85 driver detects both LM85B and LM85C revisions of the chip. See the
124	datasheet for a complete description of the differences. Other than
125	identifying the chip, the driver behaves no differently with regard to
126	these two chips. The LM85B is recommended for new designs.
127	
128	The ADM1027 and ADT7463 chips have an optional SMBALERT output that can be
129	used to signal the chipset in case a limit is exceeded or the temperature
130	sensors fail. Individual sensor interrupts can be masked so they won't
131	trigger SMBALERT. The SMBALERT output if configured replaces one of the other
132	functions (PWM2 or IN0). This functionality is not implemented in current
133	driver.
134	
135	The ADT7463 also has an optional THERM output/input which can be connected
136	to the processor PROC_HOT output. If available, the autofan control
137	dynamic Tmin feature can be enabled to keep the system temperature within
138	spec (just?!) with the least possible fan noise.
139	
140	Configuration Notes
141	-------------------
142	
143	Besides standard interfaces driver adds following:
144	
145	* Temperatures and Zones
146	
147	Each temperature sensor is associated with a Zone. There are three
148	sensors and therefore three zones (# 1, 2 and 3). Each zone has the following
149	temperature configuration points:
150	
151	* temp#_auto_temp_off - temperature below which fans should be off or spinning very low.
152	* temp#_auto_temp_min - temperature over which fans start to spin.
153	* temp#_auto_temp_max - temperature when fans spin at full speed.
154	* temp#_auto_temp_crit - temperature when all fans will run full speed.
155	
156	* PWM Control
157	
158	There are three PWM outputs. The LM85 datasheet suggests that the
159	pwm3 output control both fan3 and fan4. Each PWM can be individually
160	configured and assigned to a zone for it's control value. Each PWM can be
161	configured individually according to the following options.
162	
163	* pwm#_auto_pwm_min - this specifies the PWM value for temp#_auto_temp_off
164	                      temperature. (PWM value from 0 to 255)
165	
166	* pwm#_auto_pwm_minctl - this flags selects for temp#_auto_temp_off temperature
167	                         the behaviour of fans. Write 1 to let fans spinning at
168				 pwm#_auto_pwm_min or write 0 to let them off.
169	
170	NOTE: It has been reported that there is a bug in the LM85 that causes the flag
171	to be associated with the zones not the PWMs. This contradicts all the
172	published documentation. Setting pwm#_min_ctl in this case actually affects all
173	PWMs controlled by zone '#'.
174	
175	* PWM Controlling Zone selection
176	
177	* pwm#_auto_channels - controls zone that is associated with PWM
178	
179	Configuration choices:
180	
181	   Value     Meaning
182	  ------  ------------------------------------------------
183	      1    Controlled by Zone 1
184	      2    Controlled by Zone 2
185	      3    Controlled by Zone 3
186	     23    Controlled by higher temp of Zone 2 or 3
187	    123    Controlled by highest temp of Zone 1, 2 or 3
188	      0    PWM always 0%  (off)
189	     -1    PWM always 100%  (full on)
190	     -2    Manual control (write to 'pwm#' to set)
191	
192	The National LM85's have two vendor specific configuration
193	features. Tach. mode and Spinup Control. For more details on these,
194	see the LM85 datasheet or Application Note AN-1260. These features
195	are not currently supported by the lm85 driver.
196	
197	The Analog Devices ADM1027 has several vendor specific enhancements.
198	The number of pulses-per-rev of the fans can be set, Tach monitoring
199	can be optimized for PWM operation, and an offset can be applied to
200	the temperatures to compensate for systemic errors in the
201	measurements. These features are not currently supported by the lm85
202	driver.
203	
204	In addition to the ADM1027 features, the ADT7463 also has Tmin control
205	and THERM asserted counts. Automatic Tmin control acts to adjust the
206	Tmin value to maintain the measured temperature sensor at a specified
207	temperature. There isn't much documentation on this feature in the
208	ADT7463 data sheet. This is not supported by current driver.
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