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

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

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!

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