lm85.rst 11 KB

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  1. Kernel driver lm85
  2. ==================
  3. Supported chips:
  4. * National Semiconductor LM85 (B and C versions)
  5. Prefix: 'lm85b' or 'lm85c'
  6. Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  7. Datasheet: http://www.national.com/pf/LM/LM85.html
  8. * Texas Instruments LM96000
  9. Prefix: 'lm9600'
  10. Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  11. Datasheet: https://www.ti.com/lit/ds/symlink/lm96000.pdf
  12. * Analog Devices ADM1027
  13. Prefix: 'adm1027'
  14. Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  15. Datasheet: https://www.onsemi.com/PowerSolutions/product.do?id=ADM1027
  16. * Analog Devices ADT7463
  17. Prefix: 'adt7463'
  18. Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  19. Datasheet: https://www.onsemi.com/PowerSolutions/product.do?id=ADT7463
  20. * Analog Devices ADT7468
  21. Prefix: 'adt7468'
  22. Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  23. Datasheet: https://www.onsemi.com/PowerSolutions/product.do?id=ADT7468
  24. * SMSC EMC6D100, SMSC EMC6D101
  25. Prefix: 'emc6d100'
  26. Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  27. Datasheet: http://www.smsc.com/media/Downloads_Public/discontinued/6d100.pdf
  28. * SMSC EMC6D102
  29. Prefix: 'emc6d102'
  30. Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  31. Datasheet: http://www.smsc.com/main/catalog/emc6d102.html
  32. * SMSC EMC6D103
  33. Prefix: 'emc6d103'
  34. Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  35. Datasheet: http://www.smsc.com/main/catalog/emc6d103.html
  36. * SMSC EMC6D103S
  37. Prefix: 'emc6d103s'
  38. Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  39. Datasheet: http://www.smsc.com/main/catalog/emc6d103s.html
  40. Authors:
  41. - Philip Pokorny <ppokorny@penguincomputing.com>,
  42. - Frodo Looijaard <frodol@dds.nl>,
  43. - Richard Barrington <rich_b_nz@clear.net.nz>,
  44. - Margit Schubert-While <margitsw@t-online.de>,
  45. - Justin Thiessen <jthiessen@penguincomputing.com>
  46. Description
  47. -----------
  48. This driver implements support for the National Semiconductor LM85 and
  49. compatible chips including the Analog Devices ADM1027, ADT7463, ADT7468 and
  50. SMSC EMC6D10x chips family.
  51. The LM85 uses the 2-wire interface compatible with the SMBUS 2.0
  52. specification. Using an analog to digital converter it measures three (3)
  53. temperatures and five (5) voltages. It has four (4) 16-bit counters for
  54. measuring fan speed. Five (5) digital inputs are provided for sampling the
  55. VID signals from the processor to the VRM. Lastly, there are three (3) PWM
  56. outputs that can be used to control fan speed.
  57. The voltage inputs have internal scaling resistors so that the following
  58. voltage can be measured without external resistors:
  59. 2.5V, 3.3V, 5V, 12V, and CPU core voltage (2.25V)
  60. The temperatures measured are one internal diode, and two remote diodes.
  61. Remote 1 is generally the CPU temperature. These inputs are designed to
  62. measure a thermal diode like the one in a Pentium 4 processor in a socket
  63. 423 or socket 478 package. They can also measure temperature using a
  64. transistor like the 2N3904.
  65. A sophisticated control system for the PWM outputs is designed into the
  66. LM85 that allows fan speed to be adjusted automatically based on any of the
  67. three temperature sensors. Each PWM output is individually adjustable and
  68. programmable. Once configured, the LM85 will adjust the PWM outputs in
  69. response to the measured temperatures without further host intervention.
  70. This feature can also be disabled for manual control of the PWM's.
  71. Each of the measured inputs (voltage, temperature, fan speed) has
  72. corresponding high/low limit values. The LM85 will signal an ALARM if any
  73. measured value exceeds either limit.
  74. The LM85 samples all inputs continuously. The lm85 driver will not read
  75. the registers more often than once a second. Further, configuration data is
  76. only read once each 5 minutes. There is twice as much config data as
  77. measurements, so this would seem to be a worthwhile optimization.
  78. Special Features
  79. ----------------
  80. The LM85 has four fan speed monitoring modes. The ADM1027 has only two.
  81. Both have special circuitry to compensate for PWM interactions with the
  82. TACH signal from the fans. The ADM1027 can be configured to measure the
  83. speed of a two wire fan, but the input conditioning circuitry is different
  84. for 3-wire and 2-wire mode. For this reason, the 2-wire fan modes are not
  85. exposed to user control. The BIOS should initialize them to the correct
  86. mode. If you've designed your own ADM1027, you'll have to modify the
  87. init_client function and add an insmod parameter to set this up.
  88. To smooth the response of fans to changes in temperature, the LM85 has an
  89. optional filter for smoothing temperatures. The ADM1027 has the same
  90. config option but uses it to rate limit the changes to fan speed instead.
  91. The ADM1027, ADT7463 and ADT7468 have a 10-bit ADC and can therefore
  92. measure temperatures with 0.25 degC resolution. They also provide an offset
  93. to the temperature readings that is automatically applied during
  94. measurement. This offset can be used to zero out any errors due to traces
  95. and placement. The documentation says that the offset is in 0.25 degC
  96. steps, but in initial testing of the ADM1027 it was 1.00 degC steps. Analog
  97. Devices has confirmed this "bug". The ADT7463 is reported to work as
  98. described in the documentation. The current lm85 driver does not show the
  99. offset register.
  100. The ADT7468 has a high-frequency PWM mode, where all PWM outputs are
  101. driven by a 22.5 kHz clock. This is a global mode, not per-PWM output,
  102. which means that setting any PWM frequency above 11.3 kHz will switch
  103. all 3 PWM outputs to a 22.5 kHz frequency. Conversely, setting any PWM
  104. frequency below 11.3 kHz will switch all 3 PWM outputs to a frequency
  105. between 10 and 100 Hz, which can then be tuned separately.
  106. See the vendor datasheets for more information. There is application note
  107. from National (AN-1260) with some additional information about the LM85.
  108. The Analog Devices datasheet is very detailed and describes a procedure for
  109. determining an optimal configuration for the automatic PWM control.
  110. The SMSC EMC6D100 & EMC6D101 monitor external voltages, temperatures, and
  111. fan speeds. They use this monitoring capability to alert the system to out
  112. of limit conditions and can automatically control the speeds of multiple
  113. fans in a PC or embedded system. The EMC6D101, available in a 24-pin SSOP
  114. package, and the EMC6D100, available in a 28-pin SSOP package, are designed
  115. to be register compatible. The EMC6D100 offers all the features of the
  116. EMC6D101 plus additional voltage monitoring and system control features.
  117. Unfortunately it is not possible to distinguish between the package
  118. versions on register level so these additional voltage inputs may read
  119. zero. EMC6D102 and EMC6D103 feature additional ADC bits thus extending precision
  120. of voltage and temperature channels.
  121. SMSC EMC6D103S is similar to EMC6D103, but does not support pwm#_auto_pwm_minctl
  122. and temp#_auto_temp_off.
  123. The LM96000 supports additional high frequency PWM modes (22.5 kHz, 24 kHz,
  124. 25.7 kHz, 27.7 kHz and 30 kHz), which can be configured on a per-PWM basis.
  125. Hardware Configurations
  126. -----------------------
  127. The LM85 can be jumpered for 3 different SMBus addresses. There are
  128. no other hardware configuration options for the LM85.
  129. The lm85 driver detects both LM85B and LM85C revisions of the chip. See the
  130. datasheet for a complete description of the differences. Other than
  131. identifying the chip, the driver behaves no differently with regard to
  132. these two chips. The LM85B is recommended for new designs.
  133. The ADM1027, ADT7463 and ADT7468 chips have an optional SMBALERT output
  134. that can be used to signal the chipset in case a limit is exceeded or the
  135. temperature sensors fail. Individual sensor interrupts can be masked so
  136. they won't trigger SMBALERT. The SMBALERT output if configured replaces one
  137. of the other functions (PWM2 or IN0). This functionality is not implemented
  138. in current driver.
  139. The ADT7463 and ADT7468 also have an optional THERM output/input which can
  140. be connected to the processor PROC_HOT output. If available, the autofan
  141. control dynamic Tmin feature can be enabled to keep the system temperature
  142. within spec (just?!) with the least possible fan noise.
  143. Configuration Notes
  144. -------------------
  145. Besides standard interfaces driver adds following:
  146. * Temperatures and Zones
  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. * temp#_auto_temp_off
  151. - temperature below which fans should be off or spinning very low.
  152. * temp#_auto_temp_min
  153. - temperature over which fans start to spin.
  154. * temp#_auto_temp_max
  155. - temperature when fans spin at full speed.
  156. * temp#_auto_temp_crit
  157. - temperature when all fans will run full speed.
  158. PWM Control
  159. ^^^^^^^^^^^
  160. There are three PWM outputs. The LM85 datasheet suggests that the
  161. pwm3 output control both fan3 and fan4. Each PWM can be individually
  162. configured and assigned to a zone for its control value. Each PWM can be
  163. configured individually according to the following options.
  164. * pwm#_auto_pwm_min
  165. - this specifies the PWM value for temp#_auto_temp_off
  166. temperature. (PWM value from 0 to 255)
  167. * pwm#_auto_pwm_minctl
  168. - this flags selects for temp#_auto_temp_off temperature
  169. the behaviour of fans. Write 1 to let fans spinning at
  170. pwm#_auto_pwm_min or write 0 to let them off.
  171. .. note::
  172. It has been reported that there is a bug in the LM85 that causes
  173. the flag to be associated with the zones not the PWMs. This
  174. contradicts all the published documentation. Setting pwm#_min_ctl
  175. in this case actually affects all PWMs controlled by zone '#'.
  176. PWM Controlling Zone selection
  177. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  178. * pwm#_auto_channels
  179. - controls zone that is associated with PWM
  180. Configuration choices:
  181. ========== =============================================
  182. Value Meaning
  183. ========== =============================================
  184. 1 Controlled by Zone 1
  185. 2 Controlled by Zone 2
  186. 3 Controlled by Zone 3
  187. 23 Controlled by higher temp of Zone 2 or 3
  188. 123 Controlled by highest temp of Zone 1, 2 or 3
  189. 0 PWM always 0% (off)
  190. -1 PWM always 100% (full on)
  191. -2 Manual control (write to 'pwm#' to set)
  192. ========== =============================================
  193. The National LM85's have two vendor specific configuration
  194. features. Tach. mode and Spinup Control. For more details on these,
  195. see the LM85 datasheet or Application Note AN-1260. These features
  196. are not currently supported by the lm85 driver.
  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. In addition to the ADM1027 features, the ADT7463 and ADT7468 also have
  204. Tmin control and THERM asserted counts. Automatic Tmin control acts to
  205. adjust the Tmin value to maintain the measured temperature sensor at a
  206. specified temperature. There isn't much documentation on this feature in
  207. the ADT7463 data sheet. This is not supported by current driver.