[PATCH 11/12] drm/msm/dpu: gracefully handle null fb commits for writeback

[Dmitry Baryshkov]

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_abhinavk at 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