Re: [PATCH v8 01/15] drm/msm/disp/dpu: clear dpu_assign_crtc and get crtc from connector state instead of dpu_enc

[Dmitry Baryshkov]

On 12/10/2022 15:02, Vinod Polimera wrote:
> Update crtc retrieval from dpu_enc to dpu_enc connector state,
> since new links get set as part of the dpu enc virt mode set.
> The dpu_enc->crtc cache is no more needed, hence cleaning it as
> part of this change.
>
> Signed-off-by: Vinod Polimera <quic_vpolimer@xxxxxxxxxxx>
> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c    |  4 ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 42 +++++++++--------------------
>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h |  8 ------
>   3 files changed, 13 insertions(+), 41 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> index 13ce321..8ec9a13 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> @@ -1029,7 +1029,6 @@ static void dpu_crtc_disable(struct drm_crtc *crtc,
>   		 */
>   		if (dpu_encoder_get_intf_mode(encoder) == INTF_MODE_VIDEO)
>   			release_bandwidth = true;
> -		dpu_encoder_assign_crtc(encoder, NULL);
>   	}
>   
>   	/* wait for frame_event_done completion */
> @@ -1099,9 +1098,6 @@ static void dpu_crtc_enable(struct drm_crtc *crtc,
>   	trace_dpu_crtc_enable(DRMID(crtc), true, dpu_crtc);
>   	dpu_crtc->enabled = true;
>   
> -	drm_for_each_encoder_mask(encoder, crtc->dev, crtc->state->encoder_mask)
> -		dpu_encoder_assign_crtc(encoder, crtc);
> -
>   	/* Enable/restore vblank irq handling */
>   	drm_crtc_vblank_on(crtc);
>   }
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index 9c6817b..d05b353 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -132,11 +132,6 @@ enum dpu_enc_rc_states {
>    * @intfs_swapped:	Whether or not the phys_enc interfaces have been swapped
>    *			for partial update right-only cases, such as pingpong
>    *			split where virtual pingpong does not generate IRQs
> - * @crtc:		Pointer to the currently assigned crtc. Normally you
> - *			would use crtc->state->encoder_mask to determine the
> - *			link between encoder/crtc. However in this case we need
> - *			to track crtc in the disable() hook which is called
> - *			_after_ encoder_mask is cleared.
>    * @connector:		If a mode is set, cached pointer to the active connector
>    * @crtc_kickoff_cb:		Callback into CRTC that will flush & start
>    *				all CTL paths
> @@ -181,7 +176,6 @@ struct dpu_encoder_virt {
>   
>   	bool intfs_swapped;
>   
> -	struct drm_crtc *crtc;
>   	struct drm_connector *connector;
>   
>   	struct dentry *debugfs_root;
> @@ -1288,7 +1282,7 @@ static void dpu_encoder_vblank_callback(struct drm_encoder *drm_enc,
>   		struct dpu_encoder_phys *phy_enc)
>   {
>   	struct dpu_encoder_virt *dpu_enc = NULL;
> -	unsigned long lock_flags;
> +	struct drm_crtc *crtc;
>   
>   	if (!drm_enc || !phy_enc)
>   		return;
> @@ -1296,12 +1290,13 @@ static void dpu_encoder_vblank_callback(struct drm_encoder *drm_enc,
>   	DPU_ATRACE_BEGIN("encoder_vblank_callback");
>   	dpu_enc = to_dpu_encoder_virt(drm_enc);
>   
> -	atomic_inc(&phy_enc->vsync_cnt);
> +	if (!dpu_enc->connector || !dpu_enc->connector->state ||
> +	    !dpu_enc->connector->state->crtc)
> +		return;
>   
> -	spin_lock_irqsave(&dpu_enc->enc_spinlock, lock_flags);
> -	if (dpu_enc->crtc)
> -		dpu_crtc_vblank_callback(dpu_enc->crtc);
> -	spin_unlock_irqrestore(&dpu_enc->enc_spinlock, lock_flags);
> +	atomic_inc(&phy_enc->vsync_cnt);
> +	crtc = dpu_enc->connector->state->crtc;
> +	dpu_crtc_vblank_callback(crtc);

So, what if the user commits the mode setting change on another CPU, 
while we are handling the vblank callback here? Can this happen?

>   
>   	DPU_ATRACE_END("encoder_vblank_callback");
>   }
--
With best wishes
Dmitry