drm/i915: Empty the circular buffer when asked for a new source

So we don't read out stale CRCs from a previous run left in the buffer.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 787c50d194d4..ec9151afa240 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1820,6 +1820,12 @@ static int pipe_crc_set_source(struct drm_device *dev, enum pipe pipe,
         if (pipe_crc->source && source)
                 return -EINVAL;
 
+        /* none -> real source transition */
+        if (source) {
+                atomic_set(&pipe_crc->head, 0);
+                atomic_set(&pipe_crc->tail, 0);
+        }
+
         pipe_crc->source = source;
 
         switch (source) {