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

[Martin Peres <martin.peres@free.fr>]

On 13/04/2015 02:42, Alex Deucher wrote:
> On Sat, Apr 11, 2015 at 5:52 AM, Martin Peres <martin.peres@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@amd.com>
>>> Yeah, using 100 on a 8bit pwm timer sounds rather obviously wrong.
>>>
>>> Patch is Reviewed-by: Christian König <christian.koenig@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
Wonderful!
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