Kernel driver amc6821

Supported chips:

Texas Instruments AMC6821

Prefix: ‘amc6821’

Addresses scanned: 0x18, 0x19, 0x1a, 0x2c, 0x2d, 0x2e, 0x4c, 0x4d, 0x4e

Datasheet: http://focus.ti.com/docs/prod/folders/print/amc6821.html

Authors:

Tomaz Mertelj <tomaz.mertelj@guest.arnes.si>

Description

This driver implements support for the Texas Instruments amc6821 chip. The chip has one on-chip and one remote temperature sensor and one pwm fan regulator. The pwm can be controlled either from software or automatically.

The driver provides the following sensor accesses in sysfs:

temp1_input

ro

on-chip temperature

temp1_min

rw

temp1_max

rw

temp1_crit

rw

temp1_min_alarm

ro

temp1_max_alarm

ro

temp1_crit_alarm

ro

temp2_input

ro

remote temperature

temp2_min

rw

temp2_max

rw

temp2_crit

rw

temp2_min_alarm

ro

temp2_max_alarm

ro

temp2_crit_alarm

ro

temp2_fault

ro

fan1_input

ro

tachometer speed

fan1_min

rw

fan1_max

rw

fan1_fault

ro

fan1_pulses

rw

Pulses per revolution can be either 2 or 4.

fan1_target

rw

Target fan speed, to be used with pwm1_enable mode 4.

pwm1

rw

pwm1

pwm1_enable

rw

regulator mode, 1=open loop, 2=fan controlled by remote temperature, 3=fan controlled by combination of the on-chip temperature and remote-sensor temperature, 4=fan controlled by target rpm set with fan1_target attribute.

pwm1_mode

rw

Fan duty control mode (0=DC, 1=PWM)

pwm1_auto_channels_temp

ro

1 if pwm_enable==2, 3 if pwm_enable==3

pwm1_auto_point1_pwm

ro

Hardwired to 0, shared for both temperature channels.

pwm1_auto_point2_pwm

rw

This value is shared for both temperature channels.

pwm1_auto_point3_pwm

rw

Hardwired to 255, shared for both temperature channels.

temp1_auto_point1_temp

ro

Hardwired to temp2_auto_point1_temp which is rw. Below this temperature fan stops.

temp1_auto_point2_temp

rw

The low-temperature limit of the proportional range. Below this temperature pwm1 = pwm1_auto_point2_pwm. It can go from 0 degree C to 124 degree C in steps of 4 degree C. Read it out after writing to get the actual value.

temp1_auto_point3_temp

rw

Above this temperature fan runs at maximum speed. It can go from temp1_auto_point2_temp. It can only have certain discrete values which depend on temp1_auto_point2_temp and pwm1_auto_point2_pwm. Read it out after writing to get the actual value.

temp2_auto_point1_temp

rw

Must be between 0 degree C and 63 degree C and it defines the passive cooling temperature. Below this temperature the fan stops in the closed loop mode.

temp2_auto_point2_temp

rw

The low-temperature limit of the proportional range. Below this temperature pwm1 = pwm1_auto_point2_pwm. It can go from 0 degree C to 124 degree C in steps of 4 degree C.

temp2_auto_point3_temp

rw

Above this temperature fan runs at maximum speed. It can only have certain discrete values which depend on temp2_auto_point2_temp and pwm1_auto_point2_pwm. Read it out after writing to get actual value.

Module parameters

If your board has a BIOS that initializes the amc6821 correctly, you should load the module with: init=0.

If your board BIOS doesn’t initialize the chip, or you want different settings, you can set the following parameters:

  • init=1,

  • pwminv: 0 default pwm output, 1 inverts pwm output.