[PATCH] drm/radeon: use 0-255 rather than 0-100 for pwm fan range

[Alex Deucher]

On Sat, Apr 11, 2015 at 5:52 AM, Martin Peres <martin.peres at free.fr> wrote:
> On 05/02/2015 11:49, Christian König wrote:
>>
>> Am 04.02.2015 um 23:27 schrieb Alex Deucher:
>>>
>>> 0-255 seems to be the preferred range for the pwm interface.
>>>
>>> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
>>
>> Yeah, using 100 on a 8bit pwm timer sounds rather obviously wrong.
>>
>> Patch is Reviewed-by: Christian König <christian.koenig at amd.com>
>>
>>> ---
>>>    drivers/gpu/drm/radeon/radeon_pm.c | 8 ++++++--
>>>    1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/radeon/radeon_pm.c
>>> b/drivers/gpu/drm/radeon/radeon_pm.c
>>> index 91e1bd2..9f758d3 100644
>>> --- a/drivers/gpu/drm/radeon/radeon_pm.c
>>> +++ b/drivers/gpu/drm/radeon/radeon_pm.c
>>> @@ -585,7 +585,7 @@ static ssize_t radeon_hwmon_set_pwm1_enable(struct
>>> device *dev,
>>>         if (err)
>>>                 return err;
>>>    -    switch(value) {
>>> +       switch (value) {
>>>         case 1: /* manual, percent-based */
>>>                 rdev->asic->dpm.fan_ctrl_set_mode(rdev,
>>> FDO_PWM_MODE_STATIC);
>>>                 break;
>>> @@ -608,7 +608,7 @@ static ssize_t radeon_hwmon_get_pwm1_max(struct
>>> device *dev,
>>>                                          struct device_attribute *attr,
>>>                                          char *buf)
>>>    {
>>> -       return sprintf(buf, "%i\n", 100); /* pwm uses percent-based
>>> fan-control */
>>> +       return sprintf(buf, "%i\n", 255);
>>>    }
>
>
> This is not a standard name as it is not documented in
> https://www.kernel.org/doc/Documentation/hwmon/sysfs-interface
>
> Apparently, the pwm value should always have been exposed as 0-255 and I
> screwed it up in nouveau by having it be 0-100...
>
> Maybe we should ask pwm*_max to be defined so as new applications could do
> the right thing while not having nouveau change its ABI. I guess it is ok to
> change it for radeon as there are so few users currently but the interface
> has been in nouveau for multiple years already!
>

IIRC, I changed it in the same kernel as the original patch went in.

Alex