On 05/02/2022 00:17, Abhinav Kumar wrote:
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.

Signed-off-by: Abhinav Kumar <quic_abhin...@quicinc.com>
---
  drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c            |  9 +++++++++
  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c         | 21 +++++++++++++++++++++
  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h         |  6 ++++++
  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h    |  1 +
  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c | 12 ++++++++++++
  5 files changed, 49 insertions(+)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c 
b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
index e7c9fe1..f7963b0 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
+++ b/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_has_valid_fb(encoder)) {

Two small comments here. First, let's probably rename the function to dpu_encoder_is_valid() or dpu_encoder_is_valid_for_commit() (ugh, too long). There might be other cases (in theory), why encoder is invalid at this moment.

Also (a minor nit): I think that we should commit if at least one of encoders is valid. So we might want to create an encoder_valid_mask basing on the calls to dpu_encoder. And then use it later for calling dpu_encoder_prepare_for_kickoff() and dpu_encoder_kickoff().

+                       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");
  }
diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
index 3746432..e990dbc 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
@@ -1832,6 +1832,27 @@ void dpu_encoder_prepare_for_kickoff(struct drm_encoder 
*drm_enc)
        }
  }
+bool dpu_encoder_has_valid_fb(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.has_valid_output_fb && 
!phys->ops.has_valid_output_fb(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;
diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h 
b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
index da5b6d6..63d90b8 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
@@ -187,4 +187,10 @@ 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_has_valid_fb - cleanup writeback job for the encoder.
+ * @drm_enc:    Pointer to drm encoder structure
+ */
+bool dpu_encoder_has_valid_fb(struct drm_encoder *drm_enc);
+
  #endif /* __DPU_ENCODER_H__ */
diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h 
b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h
index 80da0a9..5b45b3c 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h
@@ -151,6 +151,7 @@ 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 (*has_valid_output_fb)(struct dpu_encoder_phys *phys_enc);
  };
/**
diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c 
b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c
index 783f83e..7eeed79 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c
@@ -717,6 +717,16 @@ 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_has_valid_fb(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
@@ -738,6 +748,8 @@ 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->has_valid_output_fb = dpu_encoder_phys_wb_has_valid_fb;
+
  }
/**


--
With best wishes
Dmitry

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