[PATCH] drm/vkms: use the gamma LUT of the state being composed

[Oarora Etimis <oaroraetimis@gmail.com>]

Compose a frame from crtc_state, but take the gamma LUT from crtc->state,
which may already be newer: the worker runs from the vblank timer and can
fall behind a commit. Such a frame combines the planes of one state with
the LUT of another; the CRC and the writeback output can then be wrong.

Read crtc_state->base.gamma_lut instead, and clear the derived fields when
there is no LUT.

Fixes: db1f254f2cfa ("drm/vkms: Add support to 1D gamma LUT")
Signed-off-by: Oarora Etimis <oaroraetimis@gmail.com>
---
 drivers/gpu/drm/vkms/vkms_composer.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
index 0fc915a954ba..ed3c8f1a8db6 100644
--- a/drivers/gpu/drm/vkms/vkms_composer.c
+++ b/drivers/gpu/drm/vkms/vkms_composer.c
@@ -609,6 +609,7 @@ void vkms_composer_worker(struct work_struct *work)
 							  struct vkms_crtc_state,
 							  composer_work);
 	struct drm_crtc *crtc = crtc_state->base.crtc;
+	struct drm_property_blob *gamma_lut = crtc_state->base.gamma_lut;
 	struct vkms_writeback_job *active_wb = crtc_state->active_writeback;
 	struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
 	bool crc_pending, wb_pending;
@@ -625,19 +626,22 @@ void vkms_composer_worker(struct work_struct *work)
 	crtc_state->frame_end = 0;
 	crtc_state->crc_pending = false;
 
-	if (crtc->state->gamma_lut) {
+	/* crtc->state may be newer than the state this frame is built from. */
+	if (gamma_lut && gamma_lut->length) {
 		s64 max_lut_index_fp;
 		s64 u16_max_fp = drm_int2fixp(0xffff);
 
-		crtc_state->gamma_lut.base = (struct drm_color_lut *)crtc->state->gamma_lut->data;
+		crtc_state->gamma_lut.base = (struct drm_color_lut *)gamma_lut->data;
 		crtc_state->gamma_lut.lut_length =
-			crtc->state->gamma_lut->length / sizeof(struct drm_color_lut);
+			gamma_lut->length / sizeof(struct drm_color_lut);
 		max_lut_index_fp = drm_int2fixp(crtc_state->gamma_lut.lut_length - 1);
-		crtc_state->gamma_lut.channel_value2index_ratio = drm_fixp_div(max_lut_index_fp,
-									       u16_max_fp);
+		crtc_state->gamma_lut.channel_value2index_ratio =
+			drm_fixp_div(max_lut_index_fp, u16_max_fp);
 
 	} else {
 		crtc_state->gamma_lut.base = NULL;
+		crtc_state->gamma_lut.lut_length = 0;
+		crtc_state->gamma_lut.channel_value2index_ratio = 0;
 	}
 
 	spin_unlock_irq(&out->composer_lock);
-- 
2.55.0