[PATCH] drm/amdgpu: For virtual_display feature, define a variable for vblank count of cpu vsync timer.

[Michel Dänzer]

On 16/08/16 03:28 PM, Deng, Emily wrote:
>> From: Michel Dänzer [mailto:michel at daenzer.net]
>> Sent: Tuesday, August 16, 2016 12:01 PM
>> On 16/08/16 12:49 PM, Deng, Emily wrote:
>>> Hi Michel, Thanks, I still couldn't see the issue that use a variable
>>> to calculate the vblank count when vsync timer interrupt occurs. I
>>> just think it only emulates the hardware behavior. And the code change
>>> will only in virtual display files which won't touch drm layer. I
>>> incline to not modify the code in drm layer or amdgpu other codes,
>>> because it may lead to other issues .
>>
>> I see it basically the other way around: We are currently pretending to the DRM
>> core code that we have a reliable hardware vblank counter and timing even in
>> the virtual DCE case, when we really don't. We should stop pretending and
>> instead communicate the lack of these hardware facilities in the virtual DCE case
>> as intended, otherwise we'll probably run into issues sooner or later.
>>
> [[EmilyD]] Hi Michel, yes, you are right, we are pretending a hardware vblank counter in virtual DCE case to drm
> layer. But can you specific some cases that we must communicate with drm layer that we don't have the vblank counter.

I described all the necessary steps (that I know of; there may be more)
in https://lists.freedesktop.org/archives/amd-gfx/2016-August/001342.html .


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer