[PATCH 1/4] drm/amd/display: Check return code for CRC drm_crtc_vblank_get

[Nicholas Kazlauskas]

[Why]
The call to drm_crtc_vblank_get can fail if vblank is disabled and
we try to increment the reference.

Since drm_crtc_vblank_get internally drops the reference when it fails
it means the subsequent drm_crtc_vblank_put(...) when closing the file
drops a zero reference.

This was found via igt at kms_plane@pixel-format-pipe-A-planes.

[How]
Check the return code and return it on failure.

We wouldn't have been able to enable CRC reading anyway since vblank
wasn't enabled.

Cc: David Francis <David.Francis at amd.com>
Cc: Bhawanpreet Lakha <Bhawanpreet.Lakha at amd.com>
Cc: Leo Li <sunpeng.li at amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c
index b01256a4692e..f675626ef56b 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c
@@ -105,6 +105,7 @@ int amdgpu_dm_crtc_set_crc_source(struct drm_crtc *crtc, const char *src_name)
 	struct drm_dp_aux *aux = NULL;
 	bool enable = false;
 	bool enabled = false;
+	int ret;
 
 	enum amdgpu_dm_pipe_crc_source source = dm_parse_crc_source(src_name);
 
@@ -175,7 +176,10 @@ int amdgpu_dm_crtc_set_crc_source(struct drm_crtc *crtc, const char *src_name)
 	 */
 	enabled = amdgpu_dm_is_valid_crc_source(crtc_state->crc_src);
 	if (!enabled && enable) {
-		drm_crtc_vblank_get(crtc);
+		ret = drm_crtc_vblank_get(crtc);
+		if (ret)
+			return ret;
+
 		if (dm_is_crc_source_dprx(source)) {
 			if (drm_dp_start_crc(aux, crtc)) {
 				DRM_DEBUG_DRIVER("dp start crc failed\n");
-- 
2.17.1