Documentation/hwmon/lm90.rst

   1 Kernel driver lm90
   2 ==================
   3
   4 Supported chips:
   5
   6   * National Semiconductor LM84
   7
   8     Prefix: 'lm84'
   9
  10     Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
  11
  12     Datasheet: Publicly available at the National Semiconductor website
  13
  14   * National Semiconductor LM90
  15
  16     Prefix: 'lm90'
  17
  18     Addresses scanned: I2C 0x4c
  19
  20     Datasheet: Publicly available at the National Semiconductor website
  21
  22                http://www.national.com/pf/LM/LM90.html
  23
  24   * National Semiconductor LM89
  25
  26     Prefix: 'lm89' (no auto-detection)
  27
  28     Addresses scanned: I2C 0x4c and 0x4d
  29
  30     Datasheet: Publicly available at the National Semiconductor website
  31
  32                http://www.national.com/mpf/LM/LM89.html
  33
  34   * National Semiconductor LM99
  35
  36     Prefix: 'lm99'
  37
  38     Addresses scanned: I2C 0x4c and 0x4d
  39
  40     Datasheet: Publicly available at the National Semiconductor website
  41
  42                http://www.national.com/pf/LM/LM99.html
  43
  44   * National Semiconductor LM86
  45
  46     Prefix: 'lm86'
  47
  48     Addresses scanned: I2C 0x4c
  49
  50     Datasheet: Publicly available at the National Semiconductor website
  51
  52                http://www.national.com/mpf/LM/LM86.html
  53
  54   * Analog Devices ADM1020
  55
  56     Prefix: 'adm1020'
  57
  58     Addresses scanned: I2C 0x4c - 0x4e
  59
  60     Datasheet: Publicly available at the Analog Devices website
  61
  62   * Analog Devices ADM1021
  63
  64     Prefix: 'adm1021'
  65
  66     Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
  67
  68     Datasheet: Publicly available at the Analog Devices website
  69
  70   * Analog Devices ADM1021A/ADM1023
  71
  72     Prefix: 'adm1023'
  73
  74     Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
  75
  76     Datasheet: Publicly available at the Analog Devices website
  77
  78   * Analog Devices ADM1032
  79
  80     Prefix: 'adm1032'
  81
  82     Addresses scanned: I2C 0x4c and 0x4d
  83
  84     Datasheet: Publicly available at the ON Semiconductor website
  85
  86                https://www.onsemi.com/PowerSolutions/product.do?id=ADM1032
  87
  88   * Analog Devices ADT7461
  89
  90     Prefix: 'adt7461'
  91
  92     Addresses scanned: I2C 0x4c and 0x4d
  93
  94     Datasheet: Publicly available at the ON Semiconductor website
  95
  96                https://www.onsemi.com/PowerSolutions/product.do?id=ADT7461
  97
  98   * Analog Devices ADT7461A
  99
 100     Prefix: 'adt7461a'
 101
 102     Addresses scanned: I2C 0x4c and 0x4d
 103
 104     Datasheet: Publicly available at the ON Semiconductor website
 105
 106                https://www.onsemi.com/PowerSolutions/product.do?id=ADT7461A
 107
 108   * Analog Devices ADT7481
 109
 110     Prefix: 'adt7481'
 111
 112     Addresses scanned: I2C 0x4b and 0x4c
 113
 114     Datasheet: Publicly available at the ON Semiconductor website
 115
 116                https://www.onsemi.com/PowerSolutions/product.do?id=ADT7481
 117
 118   * Analog Devices ADT7482
 119
 120     Prefix: 'adt7482'
 121
 122     Addresses scanned: I2C 0x4c
 123
 124     Datasheet: Publicly available at the ON Semiconductor website
 125
 126                https://www.onsemi.com/PowerSolutions/product.do?id=ADT7482
 127
 128   * Analog Devices ADT7483A
 129
 130     Prefix: 'adt7483a'
 131
 132     Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b, 0x4c, 0x4d, 0x4e
 133
 134     Datasheet: Publicly available at the ON Semiconductor website
 135
 136                https://www.onsemi.com/PowerSolutions/product.do?id=ADT7483A
 137
 138   * ON Semiconductor NCT1008
 139
 140     Prefix: 'nct1008'
 141
 142     Addresses scanned: I2C 0x4c and 0x4d
 143
 144     Datasheet: Publicly available at the ON Semiconductor website
 145
 146                https://www.onsemi.com/PowerSolutions/product.do?id=NCT1008
 147
 148   * ON Semiconductor NCT210
 149
 150     Prefix: 'adm1021'
 151
 152     Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
 153
 154     Datasheet: Publicly available at the ON Semiconductor website
 155
 156                https://www.onsemi.com/PowerSolutions/product.do?id=NCT210
 157
 158   * ON Semiconductor NCT214
 159
 160     Prefix: 'nct214'
 161
 162     Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
 163
 164     Datasheet: Publicly available at the ON Semiconductor website
 165
 166                https://www.onsemi.com/PowerSolutions/product.do?id=NCT214
 167
 168   * ON Semiconductor NCT218
 169
 170     Prefix: 'nct218'
 171
 172     Addresses scanned: I2C 0x4c - 0x4d
 173
 174     Datasheet: Publicly available at the ON Semiconductor website
 175
 176                https://www.onsemi.com/PowerSolutions/product.do?id=NCT218
 177
 178   * ON Semiconductor NCT72
 179
 180     Prefix: 'nct72'
 181
 182     Addresses scanned: I2C 0x4c - 0x4d
 183
 184     Datasheet: Publicly available at the ON Semiconductor website
 185
 186                https://www.onsemi.com/PowerSolutions/product.do?id=NCT72
 187
 188   * Maxim MAX1617
 189
 190     Prefix: 'max1617'
 191
 192     Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
 193
 194     Datasheet: Publicly available at the Maxim website
 195
 196   * Maxim MAX1617A
 197
 198     Prefix: 'max1617a'
 199
 200     Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
 201
 202     Datasheet: Publicly available at the Maxim website
 203
 204   * Maxim MAX6642
 205
 206     Prefix: 'max6642'
 207
 208     Addresses scanned: I2C 0x48-0x4f
 209
 210     Datasheet: Publicly available at the Maxim website
 211
 212                http://datasheets.maxim-ic.com/en/ds/MAX6642.pdf
 213
 214   * Maxim MAX6646
 215
 216     Prefix: 'max6646'
 217
 218     Addresses scanned: I2C 0x4d
 219
 220     Datasheet: Publicly available at the Maxim website
 221
 222                http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
 223
 224   * Maxim MAX6647
 225
 226     Prefix: 'max6646'
 227
 228     Addresses scanned: I2C 0x4e
 229
 230     Datasheet: Publicly available at the Maxim website
 231
 232                http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
 233
 234   * Maxim MAX6648
 235
 236     Prefix: 'max6648'
 237
 238     Addresses scanned: I2C 0x4c
 239
 240     Datasheet: Publicly available at the Maxim website
 241
 242                http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500
 243
 244   * Maxim MAX6649
 245
 246     Prefix: 'max6646'
 247
 248     Addresses scanned: I2C 0x4c
 249
 250     Datasheet: Publicly available at the Maxim website
 251
 252                http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
 253
 254   * Maxim MAX6654
 255
 256     Prefix: 'max6654'
 257
 258     Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
 259
 260                            0x4c, 0x4d and 0x4e
 261
 262     Datasheet: Publicly available at the Maxim website
 263
 264                https://www.maximintegrated.com/en/products/sensors/MAX6654.html
 265
 266   * Maxim MAX6657
 267
 268     Prefix: 'max6657'
 269
 270     Addresses scanned: I2C 0x4c
 271
 272     Datasheet: Publicly available at the Maxim website
 273
 274                http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
 275
 276   * Maxim MAX6658
 277
 278     Prefix: 'max6657'
 279
 280     Addresses scanned: I2C 0x4c
 281
 282     Datasheet: Publicly available at the Maxim website
 283
 284                http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
 285
 286   * Maxim MAX6659
 287
 288     Prefix: 'max6659'
 289
 290     Addresses scanned: I2C 0x4c, 0x4d, 0x4e
 291
 292     Datasheet: Publicly available at the Maxim website
 293
 294                http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
 295
 296   * Maxim MAX6680
 297
 298     Prefix: 'max6680'
 299
 300     Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
 301
 302                            0x4c, 0x4d and 0x4e
 303
 304     Datasheet: Publicly available at the Maxim website
 305
 306                http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370
 307
 308   * Maxim MAX6681
 309
 310     Prefix: 'max6680'
 311
 312     Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
 313
 314                            0x4c, 0x4d and 0x4e
 315
 316     Datasheet: Publicly available at the Maxim website
 317
 318                http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370
 319
 320   * Maxim MAX6692
 321
 322     Prefix: 'max6648'
 323
 324     Addresses scanned: I2C 0x4c
 325
 326     Datasheet: Publicly available at the Maxim website
 327
 328                http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500
 329
 330   * Maxim MAX6695
 331
 332     Prefix: 'max6695'
 333
 334     Addresses scanned: I2C 0x18
 335
 336     Datasheet: Publicly available at the Maxim website
 337
 338                http://www.maxim-ic.com/datasheet/index.mvp/id/4199
 339
 340   * Maxim MAX6696
 341
 342     Prefix: 'max6695'
 343
 344     Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
 345
 346                            0x4c, 0x4d and 0x4e
 347
 348     Datasheet: Publicly available at the Maxim website
 349
 350                http://www.maxim-ic.com/datasheet/index.mvp/id/4199
 351
 352   * Winbond/Nuvoton W83L771W/G
 353
 354     Prefix: 'w83l771'
 355
 356     Addresses scanned: I2C 0x4c
 357
 358     Datasheet: No longer available
 359
 360   * Winbond/Nuvoton W83L771AWG/ASG
 361
 362     Prefix: 'w83l771'
 363
 364     Addresses scanned: I2C 0x4c
 365
 366     Datasheet: Not publicly available, can be requested from Nuvoton
 367
 368   * Philips/NXP SA56004X
 369
 370     Prefix: 'sa56004'
 371
 372     Addresses scanned: I2C 0x48 through 0x4F
 373
 374     Datasheet: Publicly available at NXP website
 375
 376                http://ics.nxp.com/products/interface/datasheet/sa56004x.pdf
 377
 378   * GMT G781
 379
 380     Prefix: 'g781'
 381
 382     Addresses scanned: I2C 0x4c, 0x4d
 383
 384     Datasheet: Not publicly available from GMT
 385
 386   * Texas Instruments TMP451
 387
 388     Prefix: 'tmp451'
 389
 390     Addresses scanned: I2C 0x4c
 391
 392     Datasheet: Publicly available at TI website
 393
 394                https://www.ti.com/litv/pdf/sbos686
 395
 396   * Texas Instruments TMP461
 397
 398     Prefix: 'tmp461'
 399
 400     Addresses scanned: I2C 0x48 through 0x4F
 401
 402     Datasheet: Publicly available at TI website
 403
 404                https://www.ti.com/lit/gpn/tmp461
 405
 406   * Philips NE1617, NE1617A
 407
 408     Prefix: 'max1617' (probably detected as a max1617)
 409
 410     Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
 411
 412     Datasheets: Publicly available at the Philips website
 413
 414   * Philips NE1618
 415
 416     Prefix: 'ne1618'
 417
 418     Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
 419
 420     Datasheets: Publicly available at the Philips website
 421
 422   * Genesys Logic GL523SM
 423
 424     Prefix: 'gl523sm'
 425
 426     Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
 427
 428     Datasheet:
 429
 430   * TI THMC10
 431
 432     Prefix: 'thmc10'
 433
 434     Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
 435
 436     Datasheet: Publicly available at the TI website
 437
 438   * Onsemi MC1066
 439
 440     Prefix: 'mc1066'
 441
 442     Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
 443
 444     Datasheet: Publicly available at the Onsemi website
 445
 446 Author: Jean Delvare <jdelvare@suse.de>
 447
 448
 449 Description
 450 -----------
 451
 452 The LM90 is a digital temperature sensor. It senses its own temperature as
 453 well as the temperature of up to one external diode. It is compatible
 454 with many other devices, many of which are supported by this driver.
 455
 456 The family of chips supported by this driver is derived from MAX1617.
 457 This chip as well as various compatible chips support a local and a remote
 458 temperature sensor with 8 bit accuracy. Later chips provide improved accuracy
 459 and other additional features such as hysteresis and temperature offset
 460 registers.
 461
 462 Note that there is no easy way to differentiate between the MAX6657,
 463 MAX6658 and MAX6659 variants. The extra features of the MAX6659 are only
 464 supported by this driver if the chip is located at address 0x4d or 0x4e,
 465 or if the chip type is explicitly selected as max6659.
 466 The MAX6680 and MAX6681 only differ in their pinout, therefore they obviously
 467 can't (and don't need to) be distinguished.
 468
 469 The different chipsets of the family are not strictly identical, although
 470 very similar. For reference, here comes a non-exhaustive list of specific
 471 features:
 472
 473 LM84:
 474   * 8 bit sensor resolution
 475
 476 ADM1020, ADM1021, GL523SM, MAX1617, NE1617, NE1617A, THMC10:
 477   * 8 bit sensor resolution
 478   * Low temperature limits
 479
 480 NCT210, NE1618:
 481   * 11 bit sensor resolution for remote temperature sensor
 482   * Low temperature limits
 483
 484 ADM1021A, ADM1023:
 485   * Temperature offset register for remote temperature sensor
 486   * 11 bit resolution for remote temperature sensor
 487   * Low temperature limits
 488
 489 LM90:
 490   * 11 bit resolution for remote temperature sensor
 491   * Temperature offset register for remote temperature sensor
 492   * Low and critical temperature limits
 493   * Configurable conversion rate
 494   * Filter and alert configuration register at 0xBF.
 495   * ALERT is triggered by temperatures over critical limits.
 496
 497 LM86 and LM89:
 498   * Same as LM90
 499   * Better external channel accuracy
 500
 501 LM99:
 502   * Same as LM89
 503   * External temperature shifted by 16 degrees down
 504
 505 ADM1032:
 506   * Consecutive alert register at 0x22.
 507   * Conversion averaging.
 508   * Up to 64 conversions/s.
 509   * ALERT is triggered by open remote sensor.
 510   * SMBus PEC support for Write Byte and Receive Byte transactions.
 511
 512 ADT7461, ADT7461A, NCT1008:
 513   * Extended temperature range (breaks compatibility)
 514   * Lower resolution for remote temperature
 515   * SMBus PEC support for Write Byte and Receive Byte transactions.
 516   * 10 bit temperature resolution
 517
 518 ADT7481, ADT7482, ADT7483:
 519   * Temperature offset register
 520   * SMBus PEC support
 521   * 10 bit temperature resolution for external sensors
 522   * Two remote sensors
 523   * Selectable address (ADT7483)
 524
 525 MAX6642:
 526   * No critical limit register
 527   * Conversion rate not configurable
 528   * Better local resolution (10 bit)
 529   * 10 bit external sensor resolution
 530
 531 MAX6646, MAX6647, MAX6649:
 532   * Better local resolution
 533   * Extended range unsigned external temperature
 534
 535 MAX6648, MAX6692:
 536   * Better local resolution
 537   * Unsigned temperature
 538
 539 MAX6654, MAX6690:
 540   * Better local resolution
 541   * Selectable address
 542   * Remote sensor type selection
 543   * Extended temperature range
 544   * Extended resolution only available when conversion rate <= 1 Hz
 545
 546 MAX6657 and MAX6658:
 547   * Better local resolution
 548   * Remote sensor type selection
 549
 550 MAX6659:
 551   * Better local resolution
 552   * Selectable address
 553   * Second critical temperature limit
 554   * Remote sensor type selection
 555
 556 MAX6680 and MAX6681:
 557   * Selectable address
 558   * Remote sensor type selection
 559
 560 MAX6695 and MAX6696:
 561   * Better local resolution
 562   * Selectable address (max6696)
 563   * Second critical temperature limit
 564   * Two remote sensors
 565
 566 W83L771W/G
 567   * The G variant is lead-free, otherwise similar to the W.
 568   * Filter and alert configuration register at 0xBF
 569   * Moving average (depending on conversion rate)
 570
 571 W83L771AWG/ASG
 572   * Successor of the W83L771W/G, same features.
 573   * The AWG and ASG variants only differ in package format.
 574   * Diode ideality factor configuration (remote sensor) at 0xE3
 575
 576 SA56004X:
 577   * Better local resolution
 578
 579 All temperature values are given in degrees Celsius. Resolution
 580 is 1.0 degree for the local temperature, 0.125 degree for the remote
 581 temperature, except for the MAX6654, MAX6657, MAX6658 and MAX6659 which have
 582 a resolution of 0.125 degree for both temperatures.
 583
 584 Each sensor has its own high and low limits, plus a critical limit.
 585 Additionally, there is a relative hysteresis value common to both critical
 586 values. To make life easier to user-space applications, two absolute values
 587 are exported, one for each channel, but these values are of course linked.
 588 Only the local hysteresis can be set from user-space, and the same delta
 589 applies to the remote hysteresis.
 590
 591 The lm90 driver will not update its values more frequently than configured with
 592 the update_interval attribute; reading them more often will do no harm, but will
 593 return 'old' values.
 594
 595 SMBus Alert Support
 596 -------------------
 597
 598 This driver has basic support for SMBus alert. When an alert is received,
 599 the status register is read and the faulty temperature channel is logged.
 600
 601 The Analog Devices chips (ADM1032, ADT7461 and ADT7461A) and ON
 602 Semiconductor chips (NCT1008) do not implement the SMBus alert protocol
 603 properly so additional care is needed: the ALERT output is disabled when
 604 an alert is received, and is re-enabled only when the alarm is gone.
 605 Otherwise the chip would block alerts from other chips in the bus as long
 606 as the alarm is active.
 607
 608 PEC Support
 609 -----------
 610
 611 The ADM1032 is the only chip of the family which supports PEC. It does
 612 not support PEC on all transactions though, so some care must be taken.
 613
 614 When reading a register value, the PEC byte is computed and sent by the
 615 ADM1032 chip. However, in the case of a combined transaction (SMBus Read
 616 Byte), the ADM1032 computes the CRC value over only the second half of
 617 the message rather than its entirety, because it thinks the first half
 618 of the message belongs to a different transaction. As a result, the CRC
 619 value differs from what the SMBus master expects, and all reads fail.
 620
 621 For this reason, the lm90 driver will enable PEC for the ADM1032 only if
 622 the bus supports the SMBus Send Byte and Receive Byte transaction types.
 623 These transactions will be used to read register values, instead of
 624 SMBus Read Byte, and PEC will work properly.
 625
 626 Additionally, the ADM1032 doesn't support SMBus Send Byte with PEC.
 627 Instead, it will try to write the PEC value to the register (because the
 628 SMBus Send Byte transaction with PEC is similar to a Write Byte transaction
 629 without PEC), which is not what we want. Thus, PEC is explicitly disabled
 630 on SMBus Send Byte transactions in the lm90 driver.
 631
 632 PEC on byte data transactions represents a significant increase in bandwidth
 633 usage (+33% for writes, +25% for reads) in normal conditions. With the need
 634 to use two SMBus transaction for reads, this overhead jumps to +50%. Worse,
 635 two transactions will typically mean twice as much delay waiting for
 636 transaction completion, effectively doubling the register cache refresh time.
 637 I guess reliability comes at a price, but it's quite expensive this time.
 638
 639 So, as not everyone might enjoy the slowdown, PEC is disabled by default and
 640 can be enabled through sysfs. Just write 1 to the "pec" file and PEC will be
 641 enabled. Write 0 to that file to disable PEC again.