[PATCH v2] drm/amdgpu: Add DC feature mask to disable fractional pwm

[Li, Sun peng (Leo)]

On 2019-10-23 10:19 a.m., Lukáš Krejčí wrote:
> On Mon, 2019-10-21 at 15:44 -0400, sunpeng.li at amd.com wrote:
>> From: Leo Li <sunpeng.li at amd.com>
>>
>> [Why]
>>
>> Some LED panel drivers might not like fractional PWM. In such cases,
>> backlight flickering may be observed.
>>
>> [How]
>>
>> Add a DC feature mask to disable fractional PWM, and associate it with
>> the preexisting dc_config flag.
>>
>> The flag is only plumbed through the dmcu firmware, so plumb it through
>> the driver path as well.
>>
>> To disable, add the following to the linux cmdline:
>> amdgpu.dcfeaturemask=0x4
>>
>> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=204957
>> Signed-off-by: Leo Li <sunpeng.li at amd.com>
>> ---
>>
>> v2: Add bugzilla link
>>
>>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 3 +++
>>  drivers/gpu/drm/amd/display/dc/dce/dce_abm.c      | 4 ++++
>>  drivers/gpu/drm/amd/include/amd_shared.h          | 1 +
>>  3 files changed, 8 insertions(+)
> 
> Tested on Ubuntu 19.04, vanilla v5.3.7 kernel with the patch applied
> and amdgpu.dcfeaturemask=0x4 added to the kernel command line, no
> issues after 8 reboots. (The issue could be reproduced without
> amdgpu.dcfeaturemask=0x4 on first boot.)
> 
> Tested-by: Lukáš Krejčí <lskrejci at gmail.com>

Applied, thanks!
Leo