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

[Deng, Emily]

> -----Original Message-----
> From: amd-gfx [mailto:amd-gfx-bounces at lists.freedesktop.org] On Behalf Of
> Michel D?nzer
> Sent: Tuesday, August 16, 2016 2:43 PM
> To: Deng, Emily <Emily.Deng at amd.com>
> Cc: dri-devel at lists.freedesktop.org; amd-gfx at lists.freedesktop.org
> Subject: Re: [PATCH] drm/amdgpu: For virtual_display feature, define a variable
> for vblank count of cpu vsync timer.
> 
> 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 .
> 
[[EmilyD]] Hi Michel, I means can you detail the reasons or cases that we should communicate with drm layer 
when don't have the vblank counter instead of pretending a hardware vblank counter in virtual DCE case.
> 
> --
> Earthling Michel Dänzer               |               http://www.amd.com
> Libre software enthusiast             |             Mesa and X developer
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