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drm: Don't pass negative delta to ktime_sub_ns()

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It takes an unsigned value. This happens not to blow up on 64-bit
architectures, but it does on 32-bit, causing
drm_calc_vbltimestamp_from_scanoutpos() to calculate totally bogus
timestamps for vblank events. Which in turn causes e.g. gnome-shell to
hang after a DPMS off cycle with current xf86-video-ati Git.

[airlied: regression introduced in drm: use monotonic time in drm_calc_vbltimestamp_from_scanoutpos]

Cc: stable@vger.kernel.org
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=59339
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=59836
Tested-by: shui yangwei <yangweix.shui@intel.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Michel Dänzer 2013-06-12 11:58:44 +02:00 committed by Dave Airlie
parent 16d5b27250
commit e91abf80a0
1 changed files with 4 additions and 1 deletions
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5
drivers/gpu/drm/drm_irq.c
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@ -708,7 +708,10 @@ int drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev, int crtc,
/* Subtract time delta from raw timestamp to get final
* vblank_time timestamp for end of vblank.
*/
etime = ktime_sub_ns(etime, delta_ns);
if (delta_ns < 0)
etime = ktime_add_ns(etime, -delta_ns);
else
etime = ktime_sub_ns(etime, delta_ns);
*vblank_time = ktime_to_timeval(etime);
DRM_DEBUG("crtc %d : v %d p(%d,%d)@ %ld.%ld -> %ld.%ld [e %d us, %d rep]\n",