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

[Deng, Emily]

> -----Original Message-----
> From: Michel Dänzer [mailto:michel at daenzer.net]
> Sent: Tuesday, August 16, 2016 12:01 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 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.
> 
> --
> Earthling Michel Dänzer               |               http://www.amd.com
> Libre software enthusiast             |             Mesa and X developer