Commit e91abf80 authored Jun 12, 2013 by Michel Dänzer Committed by Dave Airlie Aug 08, 2013

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=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>

parent 16d5b272

drivers/gpu/drm/drm_irq.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -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);