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@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
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 The ADT7463 has a THERM asserted counter. This counter has a 22.76ms
100 resolution and a range of 5.8 seconds. The driver implements a 32-bit
101 accumulator of the counter value to extend the range to over a year. The
102 counter will stay at it's max value until read.
103
104 See the vendor datasheets for more information. There is application note
105 from National (AN-1260) with some additional information about the LM85.
106 The Analog Devices datasheet is very detailed and describes a procedure for
107 determining an optimal configuration for the automatic PWM control.
108
109 The SMSC EMC6D100 & EMC6D101 monitor external voltages, temperatures, and
110 fan speeds. They use this monitoring capability to alert the system to out
111 of limit conditions and can automatically control the speeds of multiple
112 fans in a PC or embedded system. The EMC6D101, available in a 24-pin SSOP
113 package, and the EMC6D100, available in a 28-pin SSOP package, are designed
114 to be register compatible. The EMC6D100 offers all the features of the
115 EMC6D101 plus additional voltage monitoring and system control features.
116 Unfortunately it is not possible to distinguish between the package
117 versions on register level so these additional voltage inputs may read
118 zero. The EMC6D102 features addtional ADC bits thus extending precision
119 of voltage and temperature channels.
120
121
122 Hardware Configurations
123 -----------------------
124
125 The LM85 can be jumpered for 3 different SMBus addresses. There are
126 no other hardware configuration options for the LM85.
127
128 The lm85 driver detects both LM85B and LM85C revisions of the chip. See the
129 datasheet for a complete description of the differences. Other than
130 identifying the chip, the driver behaves no differently with regard to
131 these two chips. The LM85B is recommended for new designs.
132
133 The ADM1027 and ADT7463 chips have an optional SMBALERT output that can be
134 used to signal the chipset in case a limit is exceeded or the temperature
135 sensors fail. Individual sensor interrupts can be masked so they won't
136 trigger SMBALERT. The SMBALERT output if configured replaces one of the other
137 functions (PWM2 or IN0). This functionality is not implemented in current
138 driver.
139
140 The ADT7463 also has an optional THERM output/input which can be connected
141 to the processor PROC_HOT output. If available, the autofan control
142 dynamic Tmin feature can be enabled to keep the system temperature within
143 spec (just?!) with the least possible fan noise.
144
145 Configuration Notes
146 -------------------
147
148 Besides standard interfaces driver adds following:
149
150 * Temperatures and Zones
151
152 Each temperature sensor is associated with a Zone. There are three
153 sensors and therefore three zones (# 1, 2 and 3). Each zone has the following
154 temperature configuration points:
155
156 * temp#_auto_temp_off - temperature below which fans should be off or spinning very low.
157 * temp#_auto_temp_min - temperature over which fans start to spin.
158 * temp#_auto_temp_max - temperature when fans spin at full speed.
159 * temp#_auto_temp_crit - temperature when all fans will run full speed.
160
161 * PWM Control
162
163 There are three PWM outputs. The LM85 datasheet suggests that the
164 pwm3 output control both fan3 and fan4. Each PWM can be individually
165 configured and assigned to a zone for it's control value. Each PWM can be
166 configured individually according to the following options.
167
168 * pwm#_auto_pwm_min - this specifies the PWM value for temp#_auto_temp_off
169 temperature. (PWM value from 0 to 255)
170
171 * pwm#_auto_pwm_freq - select base frequency of PWM output. You can select
172 in range of 10.0 to 94.0 Hz in .1 Hz units.
173 (Values 100 to 940).
174
175 The pwm#_auto_pwm_freq can be set to one of the following 8 values. Setting the
176 frequency to a value not on this list, will result in the next higher frequency
177 being selected. The actual device frequency may vary slightly from this
178 specification as designed by the manufacturer. Consult the datasheet for more
179 details. (PWM Frequency values: 100, 150, 230, 300, 380, 470, 620, 940)
180
181 * pwm#_auto_pwm_minctl - this flags selects for temp#_auto_temp_off temperature
182 the bahaviour of fans. Write 1 to let fans spinning at
183 pwm#_auto_pwm_min or write 0 to let them off.
184
185 NOTE: It has been reported that there is a bug in the LM85 that causes the flag
186 to be associated with the zones not the PWMs. This contradicts all the
187 published documentation. Setting pwm#_min_ctl in this case actually affects all
188 PWMs controlled by zone '#'.
189
190 * PWM Controlling Zone selection
191
192 * pwm#_auto_channels - controls zone that is associated with PWM
193
194 Configuration choices:
195
196 Value Meaning
197 ------ ------------------------------------------------
198 1 Controlled by Zone 1
199 2 Controlled by Zone 2
200 3 Controlled by Zone 3
201 23 Controlled by higher temp of Zone 2 or 3
202 123 Controlled by highest temp of Zone 1, 2 or 3
203 0 PWM always 0% (off)
204 -1 PWM always 100% (full on)
205 -2 Manual control (write to 'pwm#' to set)
206
207 The National LM85's have two vendor specific configuration
208 features. Tach. mode and Spinup Control. For more details on these,
209 see the LM85 datasheet or Application Note AN-1260.
210
211 The Analog Devices ADM1027 has several vendor specific enhancements.
212 The number of pulses-per-rev of the fans can be set, Tach monitoring
213 can be optimized for PWM operation, and an offset can be applied to
214 the temperatures to compensate for systemic errors in the
215 measurements.
216
217 In addition to the ADM1027 features, the ADT7463 also has Tmin control
218 and THERM asserted counts. Automatic Tmin control acts to adjust the
219 Tmin value to maintain the measured temperature sensor at a specified
220 temperature. There isn't much documentation on this feature in the
221 ADT7463 data sheet. This is not supported by current driver.
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