[PATCH] drm/radeon: make 64bit fences more robust

[Christian König]

Only increase the higher 32bits if we really detect a wrap around.

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=54129
https://bugs.freedesktop.org/show_bug.cgi?id=54662

Possible fixes:
https://bugzilla.redhat.com/show_bug.cgi?id=846505
https://bugzilla.redhat.com/show_bug.cgi?id=845639

Signed-off-by: Christian König <deathsimple at vodafone.de>
Cc: stable at vger.kernel.org
---
 drivers/gpu/drm/radeon/radeon_fence.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_fence.c b/drivers/gpu/drm/radeon/radeon_fence.c
index 7b737b9..4781e13 100644
--- a/drivers/gpu/drm/radeon/radeon_fence.c
+++ b/drivers/gpu/drm/radeon/radeon_fence.c
@@ -160,7 +160,7 @@ void radeon_fence_process(struct radeon_device *rdev, int ring)
 	do {
 		seq = radeon_fence_read(rdev, ring);
 		seq |= last_seq & 0xffffffff00000000LL;
-		if (seq < last_seq) {
+		if (seq < (last_seq - 0x80000000LL)) {
 			seq += 0x100000000LL;
 		}
 
@@ -811,8 +811,8 @@ static void radeon_fence_driver_init_ring(struct radeon_device *rdev, int ring)
 	rdev->fence_drv[ring].cpu_addr = NULL;
 	rdev->fence_drv[ring].gpu_addr = 0;
 	for (i = 0; i < RADEON_NUM_RINGS; ++i)
-		rdev->fence_drv[ring].sync_seq[i] = 0;
-	atomic64_set(&rdev->fence_drv[ring].last_seq, 0);
+		rdev->fence_drv[ring].sync_seq[i] = 0x100000000LL;
+	atomic64_set(&rdev->fence_drv[ring].last_seq, 0x100000000LL);
 	rdev->fence_drv[ring].last_activity = jiffies;
 	rdev->fence_drv[ring].initialized = false;
 }
-- 
1.7.9.5