[ 3.8.y.z extended stable ] Patch "drm: Don't pass negative delta to ktime_sub_ns()" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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>From d14ed8af97925140c9e53dfada0b38e1a37b0e27 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michel=20D=C3=A4nzer?= <michel.daenzer at amd.com>
Date: Wed, 12 Jun 2013 11:58:44 +0200
Subject: drm: Don't pass negative delta to ktime_sub_ns()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit e91abf80a0998f326107874c88d549f94839f13c upstream.

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]

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 at intel.com>
Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
Reviewed-by: Imre Deak <imre.deak at intel.com>
Signed-off-by: Dave Airlie <airlied at redhat.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/gpu/drm/drm_irq.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 570dac6..0f3cdda 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -704,7 +704,10 @@ 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",
--
1.8.1.2