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R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +00001Kernel driver lm85
2==================
3
4Supported 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
26Authors:
27 Philip Pokorny <ppokorny@penguincomputing.com>,
28 Frodo Looijaard <frodol@dds.nl>,
29 Richard Barrington <rich_b_nz@clear.net.nz>,
30 Margit Schubert-While <margitsw@t-online.de>,
31 Justin Thiessen <jthiessen@penguincomputing.com>
32
33Description
34-----------
35
36This driver implements support for the National Semiconductor LM85 and
37compatible chips including the Analog Devices ADM1027, ADT7463 and
38SMSC EMC6D10x chips family.
39
40The LM85 uses the 2-wire interface compatible with the SMBUS 2.0
41specification. Using an analog to digital converter it measures three (3)
42temperatures and five (5) voltages. It has four (4) 16-bit counters for
43measuring fan speed. Five (5) digital inputs are provided for sampling the
44VID signals from the processor to the VRM. Lastly, there are three (3) PWM
45outputs that can be used to control fan speed.
46
47The voltage inputs have internal scaling resistors so that the following
48voltage can be measured without external resistors:
49
50 2.5V, 3.3V, 5V, 12V, and CPU core voltage (2.25V)
51
52The temperatures measured are one internal diode, and two remote diodes.
53Remote 1 is generally the CPU temperature. These inputs are designed to
54measure a thermal diode like the one in a Pentium 4 processor in a socket
55423 or socket 478 package. They can also measure temperature using a
56transistor like the 2N3904.
57
58A sophisticated control system for the PWM outputs is designed into the
59LM85 that allows fan speed to be adjusted automatically based on any of the
60three temperature sensors. Each PWM output is individually adjustable and
61programmable. Once configured, the LM85 will adjust the PWM outputs in
62response to the measured temperatures without further host intervention.
63This feature can also be disabled for manual control of the PWM's.
64
65Each of the measured inputs (voltage, temperature, fan speed) has
66corresponding high/low limit values. The LM85 will signal an ALARM if any
67measured value exceeds either limit.
68
69The LM85 samples all inputs continuously. The lm85 driver will not read
70the registers more often than once a second. Further, configuration data is
71only read once each 5 minutes. There is twice as much config data as
72measurements, so this would seem to be a worthwhile optimization.
73
74Special Features
75----------------
76
77The LM85 has four fan speed monitoring modes. The ADM1027 has only two.
78Both have special circuitry to compensate for PWM interactions with the
79TACH signal from the fans. The ADM1027 can be configured to measure the
80speed of a two wire fan, but the input conditioning circuitry is different
81for 3-wire and 2-wire mode. For this reason, the 2-wire fan modes are not
82exposed to user control. The BIOS should initialize them to the correct
83mode. If you've designed your own ADM1027, you'll have to modify the
84init_client function and add an insmod parameter to set this up.
85
86To smooth the response of fans to changes in temperature, the LM85 has an
87optional filter for smoothing temperatures. The ADM1027 has the same
88config option but uses it to rate limit the changes to fan speed instead.
89
90The ADM1027 and ADT7463 have a 10-bit ADC and can therefore measure
91temperatures with 0.25 degC resolution. They also provide an offset to the
92temperature readings that is automatically applied during measurement.
93This offset can be used to zero out any errors due to traces and placement.
94The documentation says that the offset is in 0.25 degC steps, but in
95initial testing of the ADM1027 it was 1.00 degC steps. Analog Devices has
96confirmed this "bug". The ADT7463 is reported to work as described in the
97documentation. The current lm85 driver does not show the offset register.
98
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +000099See the vendor datasheets for more information. There is application note
100from National (AN-1260) with some additional information about the LM85.
101The Analog Devices datasheet is very detailed and describes a procedure for
102determining an optimal configuration for the automatic PWM control.
103
104The SMSC EMC6D100 & EMC6D101 monitor external voltages, temperatures, and
105fan speeds. They use this monitoring capability to alert the system to out
106of limit conditions and can automatically control the speeds of multiple
107fans in a PC or embedded system. The EMC6D101, available in a 24-pin SSOP
108package, and the EMC6D100, available in a 28-pin SSOP package, are designed
109to be register compatible. The EMC6D100 offers all the features of the
110EMC6D101 plus additional voltage monitoring and system control features.
111Unfortunately it is not possible to distinguish between the package
112versions on register level so these additional voltage inputs may read
113zero. The EMC6D102 features addtional ADC bits thus extending precision
114of voltage and temperature channels.
115
116
117Hardware Configurations
118-----------------------
119
120The LM85 can be jumpered for 3 different SMBus addresses. There are
121no other hardware configuration options for the LM85.
122
123The lm85 driver detects both LM85B and LM85C revisions of the chip. See the
124datasheet for a complete description of the differences. Other than
125identifying the chip, the driver behaves no differently with regard to
126these two chips. The LM85B is recommended for new designs.
127
128The ADM1027 and ADT7463 chips have an optional SMBALERT output that can be
129used to signal the chipset in case a limit is exceeded or the temperature
130sensors fail. Individual sensor interrupts can be masked so they won't
131trigger SMBALERT. The SMBALERT output if configured replaces one of the other
132functions (PWM2 or IN0). This functionality is not implemented in current
133driver.
134
135The ADT7463 also has an optional THERM output/input which can be connected
136to the processor PROC_HOT output. If available, the autofan control
137dynamic Tmin feature can be enabled to keep the system temperature within
138spec (just?!) with the least possible fan noise.
139
140Configuration Notes
141-------------------
142
143Besides standard interfaces driver adds following:
144
145* Temperatures and Zones
146
147Each temperature sensor is associated with a Zone. There are three
148sensors and therefore three zones (# 1, 2 and 3). Each zone has the following
149temperature 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
158There are three PWM outputs. The LM85 datasheet suggests that the
159pwm3 output control both fan3 and fan4. Each PWM can be individually
160configured and assigned to a zone for it's control value. Each PWM can be
161configured 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_freq - select base frequency of PWM output. You can select
167 in range of 10.0 to 94.0 Hz in .1 Hz units.
168 (Values 100 to 940).
169
170The pwm#_auto_pwm_freq can be set to one of the following 8 values. Setting the
171frequency to a value not on this list, will result in the next higher frequency
172being selected. The actual device frequency may vary slightly from this
173specification as designed by the manufacturer. Consult the datasheet for more
174details. (PWM Frequency values: 100, 150, 230, 300, 380, 470, 620, 940)
175
176* pwm#_auto_pwm_minctl - this flags selects for temp#_auto_temp_off temperature
177 the bahaviour of fans. Write 1 to let fans spinning at
178 pwm#_auto_pwm_min or write 0 to let them off.
179
180NOTE: It has been reported that there is a bug in the LM85 that causes the flag
181to be associated with the zones not the PWMs. This contradicts all the
182published documentation. Setting pwm#_min_ctl in this case actually affects all
183PWMs controlled by zone '#'.
184
185* PWM Controlling Zone selection
186
187* pwm#_auto_channels - controls zone that is associated with PWM
188
189Configuration choices:
190
191 Value Meaning
192 ------ ------------------------------------------------
193 1 Controlled by Zone 1
194 2 Controlled by Zone 2
195 3 Controlled by Zone 3
196 23 Controlled by higher temp of Zone 2 or 3
197 123 Controlled by highest temp of Zone 1, 2 or 3
198 0 PWM always 0% (off)
199 -1 PWM always 100% (full on)
200 -2 Manual control (write to 'pwm#' to set)
201
202The National LM85's have two vendor specific configuration
203features. Tach. mode and Spinup Control. For more details on these,
Jean Delvaredd1ac532008-05-01 08:47:33 +0200204see the LM85 datasheet or Application Note AN-1260. These features
205are not currently supported by the lm85 driver.
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000206
207The Analog Devices ADM1027 has several vendor specific enhancements.
208The number of pulses-per-rev of the fans can be set, Tach monitoring
209can be optimized for PWM operation, and an offset can be applied to
210the temperatures to compensate for systemic errors in the
Jean Delvaredd1ac532008-05-01 08:47:33 +0200211measurements. These features are not currently supported by the lm85
212driver.
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000213
214In addition to the ADM1027 features, the ADT7463 also has Tmin control
215and THERM asserted counts. Automatic Tmin control acts to adjust the
216Tmin value to maintain the measured temperature sensor at a specified
217temperature. There isn't much documentation on this feature in the
218ADT7463 data sheet. This is not supported by current driver.