[PATCHv4 2/3] Add documentation for g762 driver

[Guenter Roeck]

On Tue, Jun 04, 2013 at 09:14:47AM +0200, Arnaud Ebalard wrote:
> 
> Signed-off-by: Arnaud Ebalard <arno at natisbad.org>

Please merge the patches into one. I don't see the benefit of having three
patches as it is all part of one driver.

Thanks,
Guenter

> ---
>  Documentation/hwmon/g762 |   62 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 62 insertions(+)
>  create mode 100644 Documentation/hwmon/g762
> 
> diff --git a/Documentation/hwmon/g762 b/Documentation/hwmon/g762
> new file mode 100644
> index 0000000..8cdb0dc
> --- /dev/null
> +++ b/Documentation/hwmon/g762
> @@ -0,0 +1,62 @@
> +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_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 is also usable).
> +
> +  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.
> -- 
> 1.7.10.4
> 
>