drm/msm/dpu: gracefully handle null fb commits for writeback

kms_writeback test cases also verify with a null fb for the
writeback connector job. In addition there are also other
commit paths which can result in kickoffs without a valid
framebuffer like while closing the fb which results in the
callback to drm_atomic_helper_dirtyfb() which internally
triggers a commit.

Add protection in the dpu driver to ensure that commits for
writeback encoders without a valid fb are gracefully skipped.

changes in v2:
	- rename dpu_encoder_has_valid_fb to dpu_encoder_is_valid_for_commit

changes in v3:
	- none

Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/483522/
Link: https://lore.kernel.org/r/1650984096-9964-17-git-send-email-quic_abhinavk@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
index cdd5d95aa2ce..1ff4e91603f1 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
@@ -1862,6 +1862,27 @@ void dpu_encoder_prepare_for_kickoff(struct drm_encoder *drm_enc)
 		dpu_encoder_prep_dsc(dpu_enc, dpu_enc->dsc);
 }
 
+bool dpu_encoder_is_valid_for_commit(struct drm_encoder *drm_enc)
+{
+	struct dpu_encoder_virt *dpu_enc;
+	unsigned int i;
+	struct dpu_encoder_phys *phys;
+
+	dpu_enc = to_dpu_encoder_virt(drm_enc);
+
+	if (drm_enc->encoder_type == DRM_MODE_ENCODER_VIRTUAL) {
+		for (i = 0; i < dpu_enc->num_phys_encs; i++) {
+			phys = dpu_enc->phys_encs[i];
+			if (phys->ops.is_valid_for_commit && !phys->ops.is_valid_for_commit(phys)) {
+				DPU_DEBUG("invalid FB not kicking off\n");
+				return false;
+			}
+		}
+	}
+
+	return true;
+}
+
 void dpu_encoder_kickoff(struct drm_encoder *drm_enc)
 {
 	struct dpu_encoder_virt *dpu_enc;