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authorEgbert Eich <eich@suse.de>2012-10-13 11:36:14 +0000
committerDave Airlie <airlied@redhat.com>2012-11-20 16:07:49 +1000
commit0355cf3a0f49e26f4b84d9da7189b2324cf1df6d (patch)
treee0693690f5c6633c7be9a967914e0d5dd83fe743 /drivers
parenta4f968d8e50cb7810e08ebb9bf4c8f2b769fdac7 (diff)
DRM/KMS: Add Bail-Out Conditions for Loop.
When trying to obtain an accurate timestamp for the last vsync interrupt in vblank_disable_and_save() we loop until the vsync counter after reading the time stamp is identical to the one before. In the case where no hardware timestamp can be obtained there is probably no point in trying to make sure we remain within the same vsync during the time we obtain the counter. Furthermore we should make sure there's an 'emergency exit' so that we don't end up in an endless loop when the driver get_vblank_timestamp() function doesn't manage to return within the same vsync. This may happen when this function prints out debugging information over a slow (ie serial) line. Signed-off-by: Egbert Eich <eich@suse.de> Signed-off-by: Dave Airlie <airlied@redhat.com>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/gpu/drm/drm_irq.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index c0f0046d807..2ba9d7fac34 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -106,6 +106,7 @@ static void vblank_disable_and_save(struct drm_device *dev, int crtc)
s64 diff_ns;
int vblrc;
struct timeval tvblank;
+ int count = DRM_TIMESTAMP_MAXRETRIES;
/* Prevent vblank irq processing while disabling vblank irqs,
* so no updates of timestamps or count can happen after we've
@@ -131,7 +132,10 @@ static void vblank_disable_and_save(struct drm_device *dev, int crtc)
do {
dev->last_vblank[crtc] = dev->driver->get_vblank_counter(dev, crtc);
vblrc = drm_get_last_vbltimestamp(dev, crtc, &tvblank, 0);
- } while (dev->last_vblank[crtc] != dev->driver->get_vblank_counter(dev, crtc));
+ } while (dev->last_vblank[crtc] != dev->driver->get_vblank_counter(dev, crtc) && (--count) && vblrc);
+
+ if (!count)
+ vblrc = 0;
/* Compute time difference to stored timestamp of last vblank
* as updated by last invocation of drm_handle_vblank() in vblank irq.