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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 | ||
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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 | ||
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166 | * pwm#_auto_pwm_minctl - this flags selects for temp#_auto_temp_off temperature |
167 | the bahaviour 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, | |
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194 | see the LM85 datasheet or Application Note AN-1260. These features |
195 | are not currently supported by the lm85 driver. | |
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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 | |
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201 | measurements. These features are not currently supported by the lm85 |
202 | driver. | |
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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. |