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 --- drivers/gpu/drm/drm_irq.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index 3a3d0ce..580cdeb 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.