66 lines
3.0 KiB
Plaintext
66 lines
3.0 KiB
Plaintext
Kernel driver g762
|
|
==================
|
|
|
|
The GMT G762 Fan Speed PWM Controller is connected directly to a fan
|
|
and performs closed-loop or open-loop control of the fan speed. Two
|
|
modes - PWM or DC - are supported by the device.
|
|
|
|
For additional information, a detailed datasheet is available at
|
|
http://natisbad.org/NAS/ref/GMT_EDS-762_763-080710-0.2.pdf. sysfs
|
|
bindings are described in Documentation/hwmon/sysfs-interface.
|
|
|
|
The following entries are available to the user in a subdirectory of
|
|
/sys/bus/i2c/drivers/g762/ to control the operation of the device.
|
|
This can be done manually using the following entries but is usually
|
|
done via a userland daemon like fancontrol.
|
|
|
|
Note that those entries do not provide ways to setup the specific
|
|
hardware characteristics of the system (reference clock, pulses per
|
|
fan revolution, ...); Those can be modified via devicetree bindings
|
|
documented in Documentation/devicetree/bindings/hwmon/g762.txt or
|
|
using a specific platform_data structure in board initialization
|
|
file (see include/linux/platform_data/g762.h).
|
|
|
|
fan1_target: set desired fan speed. This only makes sense in closed-loop
|
|
fan speed control (i.e. when pwm1_enable is set to 2).
|
|
|
|
fan1_input: provide current fan rotation value in RPM as reported by
|
|
the fan to the device.
|
|
|
|
fan1_div: fan clock divisor. Supported value are 1, 2, 4 and 8.
|
|
|
|
fan1_pulses: number of pulses per fan revolution. Supported values
|
|
are 2 and 4.
|
|
|
|
fan1_fault: reports fan failure, i.e. no transition on fan gear pin for
|
|
about 0.7s (if the fan is not voluntarily set off).
|
|
|
|
fan1_alarm: in closed-loop control mode, if fan RPM value is 25% out
|
|
of the programmed value for over 6 seconds 'fan1_alarm' is
|
|
set to 1.
|
|
|
|
pwm1_enable: set current fan speed control mode i.e. 1 for manual fan
|
|
speed control (open-loop) via pwm1 described below, 2 for
|
|
automatic fan speed control (closed-loop) via fan1_target
|
|
above.
|
|
|
|
pwm1_mode: set or get fan driving mode: 1 for PWM mode, 0 for DC mode.
|
|
|
|
pwm1: get or set PWM fan control value in open-loop mode. This is an
|
|
integer value between 0 and 255. 0 stops the fan, 255 makes
|
|
it run at full speed.
|
|
|
|
Both in PWM mode ('pwm1_mode' set to 1) and DC mode ('pwm1_mode' set to 0),
|
|
when current fan speed control mode is open-loop ('pwm1_enable' set to 1),
|
|
the fan speed is programmed by setting a value between 0 and 255 via 'pwm1'
|
|
entry (0 stops the fan, 255 makes it run at full speed). In closed-loop mode
|
|
('pwm1_enable' set to 2), the expected rotation speed in RPM can be passed to
|
|
the chip via 'fan1_target'. In closed-loop mode, the target speed is compared
|
|
with current speed (available via 'fan1_input') by the device and a feedback
|
|
is performed to match that target value. The fan speed value is computed
|
|
based on the parameters associated with the physical characteristics of the
|
|
system: a reference clock source frequency, a number of pulses per fan
|
|
revolution, etc.
|
|
|
|
Note that the driver will update its values at most once per second.
|