1Kernel driver w83792d
  2=====================
  3
  4Supported chips:
  5
  6  * Winbond W83792D
  7
  8    Prefix: 'w83792d'
  9
 10    Addresses scanned: I2C 0x2c - 0x2f
 11
 12    Datasheet: http://www.winbond.com.tw
 13
 14Author: Shane Huang (Winbond)
 15Updated: Roger Lucas
 16
 17
 18Module Parameters
 19-----------------
 20
 21* init int
 22    (default 1)
 23
 24    Use 'init=0' to bypass initializing the chip.
 25    Try this if your computer crashes when you load the module.
 26
 27* force_subclients=bus,caddr,saddr,saddr
 28    This is used to force the i2c addresses for subclients of
 29    a certain chip. Example usage is `force_subclients=0,0x2f,0x4a,0x4b`
 30    to force the subclients of chip 0x2f on bus 0 to i2c addresses
 31    0x4a and 0x4b.
 32
 33
 34Description
 35-----------
 36
 37This driver implements support for the Winbond W83792AD/D.
 38
 39Detection of the chip can sometimes be foiled because it can be in an
 40internal state that allows no clean access (Bank with ID register is not
 41currently selected). If you know the address of the chip, use a 'force'
 42parameter; this will put it into a more well-behaved state first.
 43
 44The driver implements three temperature sensors, seven fan rotation speed
 45sensors, nine voltage sensors, and two automatic fan regulation
 46strategies called: Smart Fan I (Thermal Cruise mode) and Smart Fan II.
 47
 48The driver also implements up to seven fan control outputs: pwm1-7.  Pwm1-7
 49can be configured to PWM output or Analogue DC output via their associated
 50pwmX_mode. Outputs pwm4 through pwm7 may or may not be present depending on
 51how the W83792AD/D was configured by the BIOS.
 52
 53Automatic fan control mode is possible only for fan1-fan3.
 54
 55For all pwmX outputs, a value of 0 means minimum fan speed and a value of
 56255 means maximum fan speed.
 57
 58Temperatures are measured in degrees Celsius and measurement resolution is 1
 59degC for temp1 and 0.5 degC for temp2 and temp3. An alarm is triggered when
 60the temperature gets higher than the Overtemperature Shutdown value; it stays
 61on until the temperature falls below the Hysteresis value.
 62
 63Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
 64triggered if the rotation speed has dropped below a programmable limit. Fan
 65readings can be divided by a programmable divider (1, 2, 4, 8, 16, 32, 64 or
 66128) to give the readings more range or accuracy.
 67
 68Voltage sensors (also known as IN sensors) report their values in millivolts.
 69An alarm is triggered if the voltage has crossed a programmable minimum
 70or maximum limit.
 71
 72Alarms are provided as output from "realtime status register". Following bits
 73are defined:
 74
 75==== ==========
 76bit   alarm on
 77==== ==========
 780    in0
 791    in1
 802    temp1
 813    temp2
 824    temp3
 835    fan1
 846    fan2
 857    fan3
 868    in2
 879    in3
 8810   in4
 8911   in5
 9012   in6
 9113   VID change
 9214   chassis
 9315   fan7
 9416   tart1
 9517   tart2
 9618   tart3
 9719   in7
 9820   in8
 9921   fan4
10022   fan5
10123   fan6
102==== ==========
103
104Tart will be asserted while target temperature cannot be achieved after 3 minutes
105of full speed rotation of corresponding fan.
106
107In addition to the alarms described above, there is a CHAS alarm on the chips
108which triggers if your computer case is open (This one is latched, contrary
109to realtime alarms).
110
111The chips only update values each 3 seconds; reading them more often will
112do no harm, but will return 'old' values.
113
114
115W83792D PROBLEMS
116----------------
117Known problems:
118	- This driver is only for Winbond W83792D C version device, there
119	  are also some motherboards with B version W83792D device. The
120	  calculation method to in6-in7(measured value, limits) is a little
121	  different between C and B version. C or B version can be identified
122	  by CR[0x49h].
123	- The function of vid and vrm has not been finished, because I'm NOT
124	  very familiar with them. Adding support is welcome.
125	- The function of chassis open detection needs more tests.
126	- If you have ASUS server board and chip was not found: Then you will
127	  need to upgrade to latest (or beta) BIOS. If it does not help please
128	  contact us.
129
130Fan control
131-----------
132
133Manual mode
134-----------
135
136Works as expected. You just need to specify desired PWM/DC value (fan speed)
137in appropriate pwm# file.
138
139Thermal cruise
140--------------
141
142In this mode, W83792D provides the Smart Fan system to automatically control
143fan speed to keep the temperatures of CPU and the system within specific
144range. At first a wanted temperature and interval must be set. This is done
145via thermal_cruise# file. The tolerance# file serves to create T +- tolerance
146interval. The fan speed will be lowered as long as the current temperature
147remains below the thermal_cruise# +- tolerance# value. Once the temperature
148exceeds the high limit (T+tolerance), the fan will be turned on with a
149specific speed set by pwm# and automatically controlled its PWM duty cycle
150with the temperature varying. Three conditions may occur:
151
152(1) If the temperature still exceeds the high limit, PWM duty
153cycle will increase slowly.
154
155(2) If the temperature goes below the high limit, but still above the low
156limit (T-tolerance), the fan speed will be fixed at the current speed because
157the temperature is in the target range.
158
159(3) If the temperature goes below the low limit, PWM duty cycle will decrease
160slowly to 0 or a preset stop value until the temperature exceeds the low
161limit. (The preset stop value handling is not yet implemented in driver)
162
163Smart Fan II
164------------
165
166W83792D also provides a special mode for fan. Four temperature points are
167available. When related temperature sensors detects the temperature in preset
168temperature region (sf2_point@_fan# +- tolerance#) it will cause fans to run
169on programmed value from sf2_level@_fan#. You need to set four temperatures
170for each fan.
171
172
173/sys files
174----------
175
176pwm[1-7]
177	- this file stores PWM duty cycle or DC value (fan speed) in range:
178
179	    0 (stop) to 255 (full)
180pwm[1-3]_enable
181	- this file controls mode of fan/temperature control:
182
183	    * 0 Disabled
184	    * 1 Manual mode
185	    * 2 Smart Fan II
186	    * 3 Thermal Cruise
187pwm[1-7]_mode
188	- Select PWM or DC mode
189
190	    * 0 DC
191	    * 1 PWM
192thermal_cruise[1-3]
193	- Selects the desired temperature for cruise (degC)
194tolerance[1-3]
195	- Value in degrees of Celsius (degC) for +- T
196sf2_point[1-4]_fan[1-3]
197	- four temperature points for each fan for Smart Fan II
198sf2_level[1-3]_fan[1-3]
199	- three PWM/DC levels for each fan for Smart Fan II