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>

drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c

@@ -869,6 +869,13 @@ void dpu_crtc_commit_kickoff(struct drm_crtc *crtc)
 
 	DPU_ATRACE_BEGIN("crtc_commit");
 
+	drm_for_each_encoder_mask(encoder, crtc->dev,
+			crtc->state->encoder_mask) {
+		if (!dpu_encoder_is_valid_for_commit(encoder)) {
+			DRM_DEBUG_ATOMIC("invalid FB not kicking off crtc\n");
+			goto end;
+		}
+	}
 	/*
 	 * Encoder will flush/start now, unless it has a tx pending. If so, it
 	 * may delay and flush at an irq event (e.g. ppdone)
@@ -891,6 +898,8 @@ void dpu_crtc_commit_kickoff(struct drm_crtc *crtc)
 		dpu_encoder_kickoff(encoder);
 
 	reinit_completion(&dpu_crtc->frame_done_comp);
+
+end:
 	DPU_ATRACE_END("crtc_commit");
 }
 

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;

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h

@@ -196,4 +196,10 @@ void dpu_encoder_prepare_wb_job(struct drm_encoder *drm_enc,
 void dpu_encoder_cleanup_wb_job(struct drm_encoder *drm_enc,
 		struct drm_writeback_job *job);
 
+/**
+ * dpu_encoder_is_valid_for_commit - check if encode has valid parameters for commit.
+ * @drm_enc:    Pointer to drm encoder structure
+ */
+bool dpu_encoder_is_valid_for_commit(struct drm_encoder *drm_enc);
+
 #endif /* __DPU_ENCODER_H__ */

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h

@@ -142,6 +142,7 @@ struct dpu_encoder_phys_ops {
 			struct drm_writeback_job *job);
 	void (*cleanup_wb_job)(struct dpu_encoder_phys *phys_enc,
 			struct drm_writeback_job *job);
+	bool (*is_valid_for_commit)(struct dpu_encoder_phys *phys_enc);
 };
 
 /**

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c

@@ -667,6 +667,16 @@ static void dpu_encoder_phys_wb_cleanup_wb_job(struct dpu_encoder_phys *phys_enc
 	wb_enc->wb_conn = NULL;
 }
 
+static bool dpu_encoder_phys_wb_is_valid_for_commit(struct dpu_encoder_phys *phys_enc)
+{
+	struct dpu_encoder_phys_wb *wb_enc = to_dpu_encoder_phys_wb(phys_enc);
+
+	if (wb_enc->wb_job)
+		return true;
+	else
+		return false;
+}
+
 /**
  * dpu_encoder_phys_wb_init_ops - initialize writeback operations
  * @ops:	Pointer to encoder operation table
@@ -687,6 +697,8 @@ static void dpu_encoder_phys_wb_init_ops(struct dpu_encoder_phys_ops *ops)
 	ops->prepare_wb_job = dpu_encoder_phys_wb_prepare_wb_job;
 	ops->cleanup_wb_job = dpu_encoder_phys_wb_cleanup_wb_job;
 	ops->irq_control = dpu_encoder_phys_wb_irq_ctrl;
+	ops->is_valid_for_commit = dpu_encoder_phys_wb_is_valid_for_commit;
+
 }
 
 /**