linux/Documentation/hwmon/lm85
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   1Kernel driver lm85
   2==================
   3
   4Supported 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.onsemi.com/PowerSolutions/product.do?id=ADM1027
  13  * Analog Devices ADT7463
  14    Prefix: 'adt7463'
  15    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  16    Datasheet: http://www.onsemi.com/PowerSolutions/product.do?id=ADT7463
  17  * Analog Devices ADT7468
  18    Prefix: 'adt7468'
  19    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  20    Datasheet: http://www.onsemi.com/PowerSolutions/product.do?id=ADT7468
  21  * SMSC EMC6D100, SMSC EMC6D101
  22    Prefix: 'emc6d100'
  23    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  24    Datasheet: http://www.smsc.com/media/Downloads_Public/discontinued/6d100.pdf 
  25  * SMSC EMC6D102
  26    Prefix: 'emc6d102'
  27    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  28    Datasheet: http://www.smsc.com/main/catalog/emc6d102.html
  29  * SMSC EMC6D103
  30    Prefix: 'emc6d103'
  31    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  32    Datasheet: http://www.smsc.com/main/catalog/emc6d103.html
  33  * SMSC EMC6D103S
  34    Prefix: 'emc6d103s'
  35    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
  36    Datasheet: http://www.smsc.com/main/catalog/emc6d103s.html
  37
  38Authors:
  39        Philip Pokorny <ppokorny@penguincomputing.com>,
  40        Frodo Looijaard <frodol@dds.nl>,
  41        Richard Barrington <rich_b_nz@clear.net.nz>,
  42        Margit Schubert-While <margitsw@t-online.de>,
  43        Justin Thiessen <jthiessen@penguincomputing.com>
  44
  45Description
  46-----------
  47
  48This driver implements support for the National Semiconductor LM85 and
  49compatible chips including the Analog Devices ADM1027, ADT7463, ADT7468 and
  50SMSC EMC6D10x chips family.
  51
  52The LM85 uses the 2-wire interface compatible with the SMBUS 2.0
  53specification. Using an analog to digital converter it measures three (3)
  54temperatures and five (5) voltages. It has four (4) 16-bit counters for
  55measuring fan speed. Five (5) digital inputs are provided for sampling the
  56VID signals from the processor to the VRM. Lastly, there are three (3) PWM
  57outputs that can be used to control fan speed.
  58
  59The voltage inputs have internal scaling resistors so that the following
  60voltage can be measured without external resistors:
  61
  62  2.5V, 3.3V, 5V, 12V, and CPU core voltage (2.25V)
  63
  64The temperatures measured are one internal diode, and two remote diodes.
  65Remote 1 is generally the CPU temperature. These inputs are designed to
  66measure a thermal diode like the one in a Pentium 4 processor in a socket
  67423 or socket 478 package. They can also measure temperature using a
  68transistor like the 2N3904.
  69
  70A sophisticated control system for the PWM outputs is designed into the
  71LM85 that allows fan speed to be adjusted automatically based on any of the
  72three temperature sensors. Each PWM output is individually adjustable and
  73programmable. Once configured, the LM85 will adjust the PWM outputs in
  74response to the measured temperatures without further host intervention.
  75This feature can also be disabled for manual control of the PWM's.
  76
  77Each of the measured inputs (voltage, temperature, fan speed) has
  78corresponding high/low limit values. The LM85 will signal an ALARM if any
  79measured value exceeds either limit.
  80
  81The LM85 samples all inputs continuously. The lm85 driver will not read
  82the registers more often than once a second. Further, configuration data is
  83only read once each 5 minutes. There is twice as much config data as
  84measurements, so this would seem to be a worthwhile optimization.
  85
  86Special Features
  87----------------
  88
  89The LM85 has four fan speed monitoring modes. The ADM1027 has only two.
  90Both have special circuitry to compensate for PWM interactions with the
  91TACH signal from the fans. The ADM1027 can be configured to measure the
  92speed of a two wire fan, but the input conditioning circuitry is different
  93for 3-wire and 2-wire mode. For this reason, the 2-wire fan modes are not
  94exposed to user control. The BIOS should initialize them to the correct
  95mode. If you've designed your own ADM1027, you'll have to modify the
  96init_client function and add an insmod parameter to set this up.
  97
  98To smooth the response of fans to changes in temperature, the LM85 has an
  99optional filter for smoothing temperatures. The ADM1027 has the same
 100config option but uses it to rate limit the changes to fan speed instead.
 101
 102The ADM1027, ADT7463 and ADT7468 have a 10-bit ADC and can therefore
 103measure temperatures with 0.25 degC resolution. They also provide an offset
 104to the temperature readings that is automatically applied during
 105measurement. This offset can be used to zero out any errors due to traces
 106and placement. The documentation says that the offset is in 0.25 degC
 107steps, but in initial testing of the ADM1027 it was 1.00 degC steps. Analog
 108Devices has confirmed this "bug". The ADT7463 is reported to work as
 109described in the documentation. The current lm85 driver does not show the
 110offset register.
 111
 112The ADT7468 has a high-frequency PWM mode, where all PWM outputs are
 113driven by a 22.5 kHz clock. This is a global mode, not per-PWM output,
 114which means that setting any PWM frequency above 11.3 kHz will switch
 115all 3 PWM outputs to a 22.5 kHz frequency. Conversely, setting any PWM
 116frequency below 11.3 kHz will switch all 3 PWM outputs to a frequency
 117between 10 and 100 Hz, which can then be tuned separately.
 118
 119See the vendor datasheets for more information. There is application note
 120from National (AN-1260) with some additional information about the LM85.
 121The Analog Devices datasheet is very detailed and describes a procedure for
 122determining an optimal configuration for the automatic PWM control.
 123
 124The SMSC EMC6D100 & EMC6D101 monitor external voltages, temperatures, and
 125fan speeds. They use this monitoring capability to alert the system to out
 126of limit conditions and can automatically control the speeds of multiple
 127fans in a PC or embedded system. The EMC6D101, available in a 24-pin SSOP
 128package, and the EMC6D100, available in a 28-pin SSOP package, are designed
 129to be register compatible. The EMC6D100 offers all the features of the
 130EMC6D101 plus additional voltage monitoring and system control features.
 131Unfortunately it is not possible to distinguish between the package
 132versions on register level so these additional voltage inputs may read
 133zero. EMC6D102 and EMC6D103 feature additional ADC bits thus extending precision
 134of voltage and temperature channels.
 135
 136SMSC EMC6D103S is similar to EMC6D103, but does not support pwm#_auto_pwm_minctl
 137and temp#_auto_temp_off.
 138
 139Hardware Configurations
 140-----------------------
 141
 142The LM85 can be jumpered for 3 different SMBus addresses. There are
 143no other hardware configuration options for the LM85.
 144
 145The lm85 driver detects both LM85B and LM85C revisions of the chip. See the
 146datasheet for a complete description of the differences. Other than
 147identifying the chip, the driver behaves no differently with regard to
 148these two chips. The LM85B is recommended for new designs.
 149
 150The ADM1027, ADT7463 and ADT7468 chips have an optional SMBALERT output
 151that can be used to signal the chipset in case a limit is exceeded or the
 152temperature sensors fail. Individual sensor interrupts can be masked so
 153they won't trigger SMBALERT. The SMBALERT output if configured replaces one
 154of the other functions (PWM2 or IN0). This functionality is not implemented
 155in current driver.
 156
 157The ADT7463 and ADT7468 also have an optional THERM output/input which can
 158be connected to the processor PROC_HOT output. If available, the autofan
 159control dynamic Tmin feature can be enabled to keep the system temperature
 160within spec (just?!) with the least possible fan noise.
 161
 162Configuration Notes
 163-------------------
 164
 165Besides standard interfaces driver adds following:
 166
 167* Temperatures and Zones
 168
 169Each temperature sensor is associated with a Zone. There are three
 170sensors and therefore three zones (# 1, 2 and 3). Each zone has the following
 171temperature configuration points:
 172
 173* temp#_auto_temp_off - temperature below which fans should be off or spinning very low.
 174* temp#_auto_temp_min - temperature over which fans start to spin.
 175* temp#_auto_temp_max - temperature when fans spin at full speed.
 176* temp#_auto_temp_crit - temperature when all fans will run full speed.
 177
 178* PWM Control
 179
 180There are three PWM outputs. The LM85 datasheet suggests that the
 181pwm3 output control both fan3 and fan4. Each PWM can be individually
 182configured and assigned to a zone for its control value. Each PWM can be
 183configured individually according to the following options.
 184
 185* pwm#_auto_pwm_min - this specifies the PWM value for temp#_auto_temp_off
 186                      temperature. (PWM value from 0 to 255)
 187
 188* pwm#_auto_pwm_minctl - this flags selects for temp#_auto_temp_off temperature
 189                         the behaviour of fans. Write 1 to let fans spinning at
 190                         pwm#_auto_pwm_min or write 0 to let them off.
 191
 192NOTE: It has been reported that there is a bug in the LM85 that causes the flag
 193to be associated with the zones not the PWMs. This contradicts all the
 194published documentation. Setting pwm#_min_ctl in this case actually affects all
 195PWMs controlled by zone '#'.
 196
 197* PWM Controlling Zone selection
 198
 199* pwm#_auto_channels - controls zone that is associated with PWM
 200
 201Configuration choices:
 202
 203   Value     Meaning
 204  ------  ------------------------------------------------
 205      1    Controlled by Zone 1
 206      2    Controlled by Zone 2
 207      3    Controlled by Zone 3
 208     23    Controlled by higher temp of Zone 2 or 3
 209    123    Controlled by highest temp of Zone 1, 2 or 3
 210      0    PWM always 0%  (off)
 211     -1    PWM always 100%  (full on)
 212     -2    Manual control (write to 'pwm#' to set)
 213
 214The National LM85's have two vendor specific configuration
 215features. Tach. mode and Spinup Control. For more details on these,
 216see the LM85 datasheet or Application Note AN-1260. These features
 217are not currently supported by the lm85 driver.
 218
 219The Analog Devices ADM1027 has several vendor specific enhancements.
 220The number of pulses-per-rev of the fans can be set, Tach monitoring
 221can be optimized for PWM operation, and an offset can be applied to
 222the temperatures to compensate for systemic errors in the
 223measurements. These features are not currently supported by the lm85
 224driver.
 225
 226In addition to the ADM1027 features, the ADT7463 and ADT7468 also have
 227Tmin control and THERM asserted counts. Automatic Tmin control acts to
 228adjust the Tmin value to maintain the measured temperature sensor at a
 229specified temperature. There isn't much documentation on this feature in
 230the ADT7463 data sheet. This is not supported by current driver.
 231
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