Commit e91abf80 authored by Michel Dänzer's avatar Michel Dänzer Committed by Dave Airlie

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

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=59836Tested-by: default avatarshui yangwei <yangweix.shui@intel.com>
Signed-off-by: default avatarMichel Dänzer <michel.daenzer@amd.com>
Reviewed-by: default avatarImre Deak <imre.deak@intel.com>
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
parent 16d5b272
......@@ -708,6 +708,9 @@ 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.
*/
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);
......
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