linux/Documentation/hwmon/w83792d
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   1Kernel driver w83792d
   2=====================
   3
   4Supported chips:
   5  * Winbond W83792D
   6    Prefix: 'w83792d'
   7    Addresses scanned: I2C 0x2c - 0x2f
   8    Datasheet: http://www.winbond.com.tw
   9
  10Author: Chunhao Huang
  11Contact: DZShen <DZShen@Winbond.com.tw>
  12
  13
  14Module Parameters
  15-----------------
  16
  17* init int
  18  (default 1)
  19  Use 'init=0' to bypass initializing the chip.
  20  Try this if your computer crashes when you load the module.
  21
  22* force_subclients=bus,caddr,saddr,saddr
  23  This is used to force the i2c addresses for subclients of
  24  a certain chip. Example usage is `force_subclients=0,0x2f,0x4a,0x4b'
  25  to force the subclients of chip 0x2f on bus 0 to i2c addresses
  26  0x4a and 0x4b.
  27
  28
  29Description
  30-----------
  31
  32This driver implements support for the Winbond W83792AD/D.
  33
  34Detection of the chip can sometimes be foiled because it can be in an
  35internal state that allows no clean access (Bank with ID register is not
  36currently selected). If you know the address of the chip, use a 'force'
  37parameter; this will put it into a more well-behaved state first.
  38
  39The driver implements three temperature sensors, seven fan rotation speed
  40sensors, nine voltage sensors, and two automatic fan regulation
  41strategies called: Smart Fan I (Thermal Cruise mode) and Smart Fan II.
  42Automatic fan control mode is possible only for fan1-fan3. Fan4-fan7 can run
  43synchronized with selected fan (fan1-fan3). This functionality and manual PWM
  44control for fan4-fan7 is not yet implemented.
  45
  46Temperatures are measured in degrees Celsius and measurement resolution is 1
  47degC for temp1 and 0.5 degC for temp2 and temp3. An alarm is triggered when
  48the temperature gets higher than the Overtemperature Shutdown value; it stays
  49on until the temperature falls below the Hysteresis value.
  50
  51Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
  52triggered if the rotation speed has dropped below a programmable limit. Fan
  53readings can be divided by a programmable divider (1, 2, 4, 8, 16, 32, 64 or
  54128) to give the readings more range or accuracy.
  55
  56Voltage sensors (also known as IN sensors) report their values in millivolts.
  57An alarm is triggered if the voltage has crossed a programmable minimum
  58or maximum limit.
  59
  60Alarms are provided as output from "realtime status register". Following bits
  61are defined:
  62
  63bit - alarm on:
  640  - in0
  651  - in1
  662  - temp1
  673  - temp2
  684  - temp3
  695  - fan1
  706  - fan2
  717  - fan3
  728  - in2
  739  - in3
  7410 - in4
  7511 - in5
  7612 - in6
  7713 - VID change
  7814 - chassis
  7915 - fan7
  8016 - tart1
  8117 - tart2
  8218 - tart3
  8319 - in7
  8420 - in8
  8521 - fan4
  8622 - fan5
  8723 - fan6
  88
  89Tart will be asserted while target temperature cannot be achieved after 3 minutes
  90of full speed rotation of corresponding fan.
  91
  92In addition to the alarms described above, there is a CHAS alarm on the chips
  93which triggers if your computer case is open (This one is latched, contrary
  94to realtime alarms).
  95
  96The chips only update values each 3 seconds; reading them more often will
  97do no harm, but will return 'old' values.
  98
  99
 100W83792D PROBLEMS
 101----------------
 102Known problems:
 103        - This driver is only for Winbond W83792D C version device, there
 104          are also some motherboards with B version W83792D device. The
 105          calculation method to in6-in7(measured value, limits) is a little
 106          different between C and B version. C or B version can be identified
 107          by CR[0x49h].
 108        - The function of vid and vrm has not been finished, because I'm NOT
 109          very familiar with them. Adding support is welcome.
 110        - The function of chassis open detection needs more tests.
 111        - If you have ASUS server board and chip was not found: Then you will
 112          need to upgrade to latest (or beta) BIOS. If it does not help please
 113          contact us.
 114
 115Fan control
 116-----------
 117
 118Manual mode
 119-----------
 120
 121Works as expected. You just need to specify desired PWM/DC value (fan speed)
 122in appropriate pwm# file.
 123
 124Thermal cruise
 125--------------
 126
 127In this mode, W83792D provides the Smart Fan system to automatically control
 128fan speed to keep the temperatures of CPU and the system within specific
 129range. At first a wanted temperature and interval must be set. This is done
 130via thermal_cruise# file. The tolerance# file serves to create T +- tolerance
 131interval. The fan speed will be lowered as long as the current temperature
 132remains below the thermal_cruise# +- tolerance# value. Once the temperature
 133exceeds the high limit (T+tolerance), the fan will be turned on with a
 134specific speed set by pwm# and automatically controlled its PWM duty cycle
 135with the temperature varying. Three conditions may occur:
 136
 137(1) If the temperature still exceeds the high limit, PWM duty
 138cycle will increase slowly.
 139
 140(2) If the temperature goes below the high limit, but still above the low
 141limit (T-tolerance), the fan speed will be fixed at the current speed because
 142the temperature is in the target range.
 143
 144(3) If the temperature goes below the low limit, PWM duty cycle will decrease
 145slowly to 0 or a preset stop value until the temperature exceeds the low
 146limit. (The preset stop value handling is not yet implemented in driver)
 147
 148Smart Fan II
 149------------
 150
 151W83792D also provides a special mode for fan. Four temperature points are
 152available. When related temperature sensors detects the temperature in preset
 153temperature region (sf2_point@_fan# +- tolerance#) it will cause fans to run
 154on programmed value from sf2_level@_fan#. You need to set four temperatures
 155for each fan.
 156
 157
 158/sys files
 159----------
 160
 161pwm[1-3] - this file stores PWM duty cycle or DC value (fan speed) in range:
 162        0 (stop) to 255 (full)
 163pwm[1-3]_enable - this file controls mode of fan/temperature control:
 164            * 0 Disabled
 165            * 1 Manual mode
 166            * 2 Smart Fan II
 167            * 3 Thermal Cruise
 168pwm[1-3]_mode - Select PWM of DC mode
 169            * 0 DC
 170            * 1 PWM
 171thermal_cruise[1-3] - Selects the desired temperature for cruise (degC)
 172tolerance[1-3] - Value in degrees of Celsius (degC) for +- T
 173sf2_point[1-4]_fan[1-3] - four temperature points for each fan for Smart Fan II
 174sf2_level[1-3]_fan[1-3] - three PWM/DC levels for each fan for Smart Fan II
 175
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