[PATCH v2] drm/i915: clear CRTC color blob pointers after dropping refs

[Guangshuo Li <lgs201920130244@gmail.com>]

intel_crtc_free_hw_state() drops the CRTC color blob references, but
leaves the corresponding pointers unchanged.

This can matter in intel_crtc_prepare_cleared_state(), which frees the
old CRTC hw state before calling intel_dp_tunnel_atomic_clear_stream_bw().
The latter can fail while looking up the DP tunnel group state, for
example with -EDEADLK.

If that happens, the function returns without completing the cleared
state preparation. The failed atomic state will then be cleared by the
atomic core and intel_crtc_free_hw_state() can be called again for the
same state, dropping the same blob references again.

Clear the blob pointers after dropping the references so repeated cleanup
of the same CRTC hw state is safe.

Fixes: fb69d0076e68 ("drm/i915/dp_tunnel: Fix error handling when clearing stream BW in atomic state")
Suggested-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
---
v2:
  - Keep the original ordering in intel_crtc_prepare_cleared_state().
  - Clear the blob reference pointers in intel_crtc_free_hw_state(), as
    suggested by Imre.

 drivers/gpu/drm/i915/display/intel_atomic.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_atomic.c b/drivers/gpu/drm/i915/display/intel_atomic.c
index 71b7325917b6..0cdae87e4bfc 100644
--- a/drivers/gpu/drm/i915/display/intel_atomic.c
+++ b/drivers/gpu/drm/i915/display/intel_atomic.c
@@ -294,6 +294,12 @@ static void intel_crtc_put_color_blobs(struct intel_crtc_state *crtc_state)
 void intel_crtc_free_hw_state(struct intel_crtc_state *crtc_state)
 {
 	intel_crtc_put_color_blobs(crtc_state);
+
+	crtc_state->hw.degamma_lut = NULL;
+	crtc_state->hw.gamma_lut = NULL;
+	crtc_state->hw.ctm = NULL;
+	crtc_state->pre_csc_lut = NULL;
+	crtc_state->post_csc_lut = NULL;
 }
 
 /**
-- 
2.43.0