lm90.rst 11 KB

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  1. Kernel driver lm90
  2. ==================
  3. Supported chips:
  4. * National Semiconductor LM90
  5. Prefix: 'lm90'
  6. Addresses scanned: I2C 0x4c
  7. Datasheet: Publicly available at the National Semiconductor website
  8. http://www.national.com/pf/LM/LM90.html
  9. * National Semiconductor LM89
  10. Prefix: 'lm89' (no auto-detection)
  11. Addresses scanned: I2C 0x4c and 0x4d
  12. Datasheet: Publicly available at the National Semiconductor website
  13. http://www.national.com/mpf/LM/LM89.html
  14. * National Semiconductor LM99
  15. Prefix: 'lm99'
  16. Addresses scanned: I2C 0x4c and 0x4d
  17. Datasheet: Publicly available at the National Semiconductor website
  18. http://www.national.com/pf/LM/LM99.html
  19. * National Semiconductor LM86
  20. Prefix: 'lm86'
  21. Addresses scanned: I2C 0x4c
  22. Datasheet: Publicly available at the National Semiconductor website
  23. http://www.national.com/mpf/LM/LM86.html
  24. * Analog Devices ADM1032
  25. Prefix: 'adm1032'
  26. Addresses scanned: I2C 0x4c and 0x4d
  27. Datasheet: Publicly available at the ON Semiconductor website
  28. https://www.onsemi.com/PowerSolutions/product.do?id=ADM1032
  29. * Analog Devices ADT7461
  30. Prefix: 'adt7461'
  31. Addresses scanned: I2C 0x4c and 0x4d
  32. Datasheet: Publicly available at the ON Semiconductor website
  33. https://www.onsemi.com/PowerSolutions/product.do?id=ADT7461
  34. * Analog Devices ADT7461A
  35. Prefix: 'adt7461a'
  36. Addresses scanned: I2C 0x4c and 0x4d
  37. Datasheet: Publicly available at the ON Semiconductor website
  38. https://www.onsemi.com/PowerSolutions/product.do?id=ADT7461A
  39. * ON Semiconductor NCT1008
  40. Prefix: 'nct1008'
  41. Addresses scanned: I2C 0x4c and 0x4d
  42. Datasheet: Publicly available at the ON Semiconductor website
  43. https://www.onsemi.com/PowerSolutions/product.do?id=NCT1008
  44. * Maxim MAX6646
  45. Prefix: 'max6646'
  46. Addresses scanned: I2C 0x4d
  47. Datasheet: Publicly available at the Maxim website
  48. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
  49. * Maxim MAX6647
  50. Prefix: 'max6646'
  51. Addresses scanned: I2C 0x4e
  52. Datasheet: Publicly available at the Maxim website
  53. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
  54. * Maxim MAX6648
  55. Prefix: 'max6646'
  56. Addresses scanned: I2C 0x4c
  57. Datasheet: Publicly available at the Maxim website
  58. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500
  59. * Maxim MAX6649
  60. Prefix: 'max6646'
  61. Addresses scanned: I2C 0x4c
  62. Datasheet: Publicly available at the Maxim website
  63. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
  64. * Maxim MAX6654
  65. Prefix: 'max6654'
  66. Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
  67. 0x4c, 0x4d and 0x4e
  68. Datasheet: Publicly available at the Maxim website
  69. https://www.maximintegrated.com/en/products/sensors/MAX6654.html
  70. * Maxim MAX6657
  71. Prefix: 'max6657'
  72. Addresses scanned: I2C 0x4c
  73. Datasheet: Publicly available at the Maxim website
  74. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
  75. * Maxim MAX6658
  76. Prefix: 'max6657'
  77. Addresses scanned: I2C 0x4c
  78. Datasheet: Publicly available at the Maxim website
  79. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
  80. * Maxim MAX6659
  81. Prefix: 'max6659'
  82. Addresses scanned: I2C 0x4c, 0x4d, 0x4e
  83. Datasheet: Publicly available at the Maxim website
  84. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
  85. * Maxim MAX6680
  86. Prefix: 'max6680'
  87. Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
  88. 0x4c, 0x4d and 0x4e
  89. Datasheet: Publicly available at the Maxim website
  90. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370
  91. * Maxim MAX6681
  92. Prefix: 'max6680'
  93. Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
  94. 0x4c, 0x4d and 0x4e
  95. Datasheet: Publicly available at the Maxim website
  96. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370
  97. * Maxim MAX6692
  98. Prefix: 'max6646'
  99. Addresses scanned: I2C 0x4c
  100. Datasheet: Publicly available at the Maxim website
  101. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500
  102. * Maxim MAX6695
  103. Prefix: 'max6695'
  104. Addresses scanned: I2C 0x18
  105. Datasheet: Publicly available at the Maxim website
  106. http://www.maxim-ic.com/datasheet/index.mvp/id/4199
  107. * Maxim MAX6696
  108. Prefix: 'max6695'
  109. Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
  110. 0x4c, 0x4d and 0x4e
  111. Datasheet: Publicly available at the Maxim website
  112. http://www.maxim-ic.com/datasheet/index.mvp/id/4199
  113. * Winbond/Nuvoton W83L771W/G
  114. Prefix: 'w83l771'
  115. Addresses scanned: I2C 0x4c
  116. Datasheet: No longer available
  117. * Winbond/Nuvoton W83L771AWG/ASG
  118. Prefix: 'w83l771'
  119. Addresses scanned: I2C 0x4c
  120. Datasheet: Not publicly available, can be requested from Nuvoton
  121. * Philips/NXP SA56004X
  122. Prefix: 'sa56004'
  123. Addresses scanned: I2C 0x48 through 0x4F
  124. Datasheet: Publicly available at NXP website
  125. http://ics.nxp.com/products/interface/datasheet/sa56004x.pdf
  126. * GMT G781
  127. Prefix: 'g781'
  128. Addresses scanned: I2C 0x4c, 0x4d
  129. Datasheet: Not publicly available from GMT
  130. * Texas Instruments TMP451
  131. Prefix: 'tmp451'
  132. Addresses scanned: I2C 0x4c
  133. Datasheet: Publicly available at TI website
  134. https://www.ti.com/litv/pdf/sbos686
  135. * Texas Instruments TMP461
  136. Prefix: 'tmp461'
  137. Addresses scanned: I2C 0x48 through 0x4F
  138. Datasheet: Publicly available at TI website
  139. https://www.ti.com/lit/gpn/tmp461
  140. Author: Jean Delvare <jdelvare@suse.de>
  141. Description
  142. -----------
  143. The LM90 is a digital temperature sensor. It senses its own temperature as
  144. well as the temperature of up to one external diode. It is compatible
  145. with many other devices, many of which are supported by this driver.
  146. Note that there is no easy way to differentiate between the MAX6657,
  147. MAX6658 and MAX6659 variants. The extra features of the MAX6659 are only
  148. supported by this driver if the chip is located at address 0x4d or 0x4e,
  149. or if the chip type is explicitly selected as max6659.
  150. The MAX6680 and MAX6681 only differ in their pinout, therefore they obviously
  151. can't (and don't need to) be distinguished.
  152. The specificity of this family of chipsets over the ADM1021/LM84
  153. family is that it features critical limits with hysteresis, and an
  154. increased resolution of the remote temperature measurement.
  155. The different chipsets of the family are not strictly identical, although
  156. very similar. For reference, here comes a non-exhaustive list of specific
  157. features:
  158. LM90:
  159. * Filter and alert configuration register at 0xBF.
  160. * ALERT is triggered by temperatures over critical limits.
  161. LM86 and LM89:
  162. * Same as LM90
  163. * Better external channel accuracy
  164. LM99:
  165. * Same as LM89
  166. * External temperature shifted by 16 degrees down
  167. ADM1032:
  168. * Consecutive alert register at 0x22.
  169. * Conversion averaging.
  170. * Up to 64 conversions/s.
  171. * ALERT is triggered by open remote sensor.
  172. * SMBus PEC support for Write Byte and Receive Byte transactions.
  173. ADT7461, ADT7461A, NCT1008:
  174. * Extended temperature range (breaks compatibility)
  175. * Lower resolution for remote temperature
  176. MAX6654:
  177. * Better local resolution
  178. * Selectable address
  179. * Remote sensor type selection
  180. * Extended temperature range
  181. * Extended resolution only available when conversion rate <= 1 Hz
  182. MAX6657 and MAX6658:
  183. * Better local resolution
  184. * Remote sensor type selection
  185. MAX6659:
  186. * Better local resolution
  187. * Selectable address
  188. * Second critical temperature limit
  189. * Remote sensor type selection
  190. MAX6680 and MAX6681:
  191. * Selectable address
  192. * Remote sensor type selection
  193. MAX6695 and MAX6696:
  194. * Better local resolution
  195. * Selectable address (max6696)
  196. * Second critical temperature limit
  197. * Two remote sensors
  198. W83L771W/G
  199. * The G variant is lead-free, otherwise similar to the W.
  200. * Filter and alert configuration register at 0xBF
  201. * Moving average (depending on conversion rate)
  202. W83L771AWG/ASG
  203. * Successor of the W83L771W/G, same features.
  204. * The AWG and ASG variants only differ in package format.
  205. * Diode ideality factor configuration (remote sensor) at 0xE3
  206. SA56004X:
  207. * Better local resolution
  208. All temperature values are given in degrees Celsius. Resolution
  209. is 1.0 degree for the local temperature, 0.125 degree for the remote
  210. temperature, except for the MAX6654, MAX6657, MAX6658 and MAX6659 which have
  211. a resolution of 0.125 degree for both temperatures.
  212. Each sensor has its own high and low limits, plus a critical limit.
  213. Additionally, there is a relative hysteresis value common to both critical
  214. values. To make life easier to user-space applications, two absolute values
  215. are exported, one for each channel, but these values are of course linked.
  216. Only the local hysteresis can be set from user-space, and the same delta
  217. applies to the remote hysteresis.
  218. The lm90 driver will not update its values more frequently than configured with
  219. the update_interval attribute; reading them more often will do no harm, but will
  220. return 'old' values.
  221. SMBus Alert Support
  222. -------------------
  223. This driver has basic support for SMBus alert. When an alert is received,
  224. the status register is read and the faulty temperature channel is logged.
  225. The Analog Devices chips (ADM1032, ADT7461 and ADT7461A) and ON
  226. Semiconductor chips (NCT1008) do not implement the SMBus alert protocol
  227. properly so additional care is needed: the ALERT output is disabled when
  228. an alert is received, and is re-enabled only when the alarm is gone.
  229. Otherwise the chip would block alerts from other chips in the bus as long
  230. as the alarm is active.
  231. PEC Support
  232. -----------
  233. The ADM1032 is the only chip of the family which supports PEC. It does
  234. not support PEC on all transactions though, so some care must be taken.
  235. When reading a register value, the PEC byte is computed and sent by the
  236. ADM1032 chip. However, in the case of a combined transaction (SMBus Read
  237. Byte), the ADM1032 computes the CRC value over only the second half of
  238. the message rather than its entirety, because it thinks the first half
  239. of the message belongs to a different transaction. As a result, the CRC
  240. value differs from what the SMBus master expects, and all reads fail.
  241. For this reason, the lm90 driver will enable PEC for the ADM1032 only if
  242. the bus supports the SMBus Send Byte and Receive Byte transaction types.
  243. These transactions will be used to read register values, instead of
  244. SMBus Read Byte, and PEC will work properly.
  245. Additionally, the ADM1032 doesn't support SMBus Send Byte with PEC.
  246. Instead, it will try to write the PEC value to the register (because the
  247. SMBus Send Byte transaction with PEC is similar to a Write Byte transaction
  248. without PEC), which is not what we want. Thus, PEC is explicitly disabled
  249. on SMBus Send Byte transactions in the lm90 driver.
  250. PEC on byte data transactions represents a significant increase in bandwidth
  251. usage (+33% for writes, +25% for reads) in normal conditions. With the need
  252. to use two SMBus transaction for reads, this overhead jumps to +50%. Worse,
  253. two transactions will typically mean twice as much delay waiting for
  254. transaction completion, effectively doubling the register cache refresh time.
  255. I guess reliability comes at a price, but it's quite expensive this time.
  256. So, as not everyone might enjoy the slowdown, PEC can be disabled through
  257. sysfs. Just write 0 to the "pec" file and PEC will be disabled. Write 1
  258. to that file to enable PEC again.