[Bug 91562] [SKL][Linux] : Xrandr is not working as expected

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Tue Sep 8 02:22:46 PDT 2015


https://bugs.freedesktop.org/show_bug.cgi?id=91562

--- Comment #17 from Chris Wilson <chris at chris-wilson.co.uk> ---
(In reply to Tvrtko Ursulin from comment #16)
> (In reply to Chris Wilson from comment #15)
> > (In reply to Tvrtko Ursulin from comment #14)
> > > Created attachment 118122 [details]
> > > ddx debug log in Y tiling mode
> > > 
> > > With the DDX rebuilt to default to Y tiling, this logs shows that when
> > > "xrandr -o left" it abandons the Y tiled FB and goes back to X tiled.
> > 
> > It sets the rotation, and then the kernel rejects the setcrtc and so it is
> > forced to use a shadowfb, X without rotation, and perform manual rotations
> > (using the GPU of course!) from the Y-tiled frontbuffer to the X-tiled
> > framebuffer.
> 
> Does it try to go Y tiled when attempting to rotate, in the default build? 

It's tricky. The buffer cannot be exported and Y-tiling is so much slower for
common operations that I am not convinced it is worth it. It is possible for
the client to provide a Y-tiled buffer that we will then use. But since the
setcrtc failed...


> Interestingly in the Y tiled build there seems to be a path where it doesn't
> use fb modifiers ("[drm:intel_framebuffer_init] No Y tiling for legacy
> addfb").

Right, during the start up it tests whether the interface is deliberately
broken.

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