Chris Wilson writes:
> On Wed, Sep 24, 2014 at 08:17:59AM +0200, Egbert Eich wrote:
> > From: Egbert Eich <[email protected]>
> >
> > copy_front() calls sna_pixmap_force_to_gpu() which may fail. If we pretend
> > to have been successful and continue the caller sna_mode_resize() may
> > finish
> > successfully pretending a mode change has succeeded which might leave a
> > mode
> > behind which is unusable.
>
> Show me the actual bug. If the copy fails, the new framebuffer contents
> are just left uninitialised (normal X behaviour) until they get
> "immediately" redrawn. The subsequent modeset does not depend upon the screen
> Pixmap fitting into GPU memory, but that it can fit individual CRTC into
> the GTT.
Then the mode should have failed somewhere else maybe.
The underlying issue of the problem was fixed by the other
patch I have sent today. This problem caused kgem_surface_size()
to return NULL and thus kgem_create_2d() and ulitmately
sna_pixmap_force_to_gpu() to fail.
With the the other fix applied kgem_surface_size() doesn't
fail any longer for my test case - still it may fail for other
reasons.
Here is the test scenario:
Pineview Chipset, start a bare X server (without the other patch applied
to the driver), start xterm on it.
On my system 'xrandr -q' gives:
Screen 0: minimum 8 x 8, current 1366 x 768, maximum 32767 x 32767
LVDS1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 222mm x
125mm
1366x768 60.0*+
1024x768 60.0
800x600 60.3 56.2
640x480 59.9
VGA1 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)
now run 'xrandr --output LVDS1 --panning 3048x768' (or whatever
other output it uses).
Without the other patch applied kgem_surface_size() fails, without
*both* patches applied the mode set succeeds and 'xandr -q' now gives:
Screen 0: minimum 8 x 8, current 3048 x 768, maximum 32767 x 32767
LVDS1 connected 3048x768+0+0 (normal left inverted right x axis y axis) 222mm x
125mm panning 3048x768+0+0
1366x768 60.0*+
1024x768 60.0
800x600 60.3 56.2
640x480 59.9
VGA1 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)
Observation 1:
Screen doesn't pan: when moving the cursor to the right edge,
screen and cursor become out of sync, screen content doesnt get
update ie. starting a new application (like xclock) succeeds but
nothing is drawn).
Observation 2:
Terminating xterm makes the server reset which fails with
intel(0): [intel] Failed to allocate video resources for front buffer 3048x768
at depth 24
in sna_create_screen_resources() due to sna_pixmap_force_to_gpu()
failing. The reason for the failure is the same as described above.
As I said: these failures go away with the other patch I posted today
and which you OKed and the code in this patch is no longer triggered.
Still there are other conditions under which kgem_surface_size() may
return 0.
For panning one needs to be able to draw into the screen pixmap outside
of the area exposed by the crtc.
Cheers,
Egbert.
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