Re: [Freedreno] [PATCH 1/2] drm/msm: use common display thread for dispatching vblank events

[Jeykumar Sankaran <jsanka@codeaurora.org>]

On 2018-11-01 12:09, Sean Paul wrote:
> On Wed, Oct 31, 2018 at 05:19:04PM -0700, Jeykumar Sankaran wrote:
>> DPU was using one thread per display to dispatch async
>> commits and vblank requests. Since clean up already happened
>> in msm to use the common thread for all the display commits,
>> display threads are only used to cater vblank requests. Single
>> thread is sufficient to do the job without any performance hits.
>> 
>> Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>
>> ---
>>  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c |  6 +---
>>  drivers/gpu/drm/msm/msm_drv.c               | 50
> ++++++++++++-----------------
>>  drivers/gpu/drm/msm/msm_drv.h               |  2 +-
>>  3 files changed, 23 insertions(+), 35 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> index 82c55ef..aff20f5 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> @@ -753,11 +753,7 @@ static int dpu_encoder_resource_control(struct
> drm_encoder *drm_enc,
>>  	is_vid_mode = dpu_enc->disp_info.capabilities &
>>  						MSM_DISPLAY_CAP_VID_MODE;
>> 
>> -	if (drm_enc->crtc->index >= ARRAY_SIZE(priv->disp_thread)) {
>> -		DPU_ERROR("invalid crtc index\n");
>> -		return -EINVAL;
>> -	}
>> -	disp_thread = &priv->disp_thread[drm_enc->crtc->index];
>> +	disp_thread = &priv->disp_thread;
>> 
>>  	/*
>>  	 * when idle_pc is not supported, process only KICKOFF, STOP and
> MODESET
>> diff --git a/drivers/gpu/drm/msm/msm_drv.c
> b/drivers/gpu/drm/msm/msm_drv.c
>> index 9c9f7ff..1f384b3 100644
>> --- a/drivers/gpu/drm/msm/msm_drv.c
>> +++ b/drivers/gpu/drm/msm/msm_drv.c
>> @@ -257,8 +257,7 @@ static int vblank_ctrl_queue_work(struct
> msm_drm_private *priv,
>>  	list_add_tail(&vbl_ev->node, &vbl_ctrl->event_list);
>>  	spin_unlock_irqrestore(&vbl_ctrl->lock, flags);
>> 
>> -	kthread_queue_work(&priv->disp_thread[crtc_id].worker,
>> -			&vbl_ctrl->work);
>> +	kthread_queue_work(&priv->disp_thread.worker, &vbl_ctrl->work);
>> 
>>  	return 0;
>>  }
>> @@ -284,14 +283,12 @@ static int msm_drm_uninit(struct device *dev)
>>  		kfree(vbl_ev);
>>  	}
>> 
>> +	kthread_flush_worker(&priv->disp_thread.worker);
>> +	kthread_stop(priv->disp_thread.thread);
> 
> I realize this is moving existing code, but is there a race here? You
> can't have
> work enqueued in between the flush and stop?
Yes. I see only priv->kms is checked before queuing the work.

I can move the thread cleanup after the drm_mode_config_cleanup which
releases the CRTC objects. This way no one can make any further vblank 
requests.

Thanks and Regards,
Jeykumar S.
> 
> You might also want to use kthread_destroy_worker to do this work (in a
> follow-up patch including the event threads too).
> 
>> +	priv->disp_thread.thread = NULL;
>> +
>>  	/* clean up display commit/event worker threads */
> 
> This comment needs updating now
> 
>>  	for (i = 0; i < priv->num_crtcs; i++) {
>> -		if (priv->disp_thread[i].thread) {
>> -
> kthread_flush_worker(&priv->disp_thread[i].worker);
>> -			kthread_stop(priv->disp_thread[i].thread);
>> -			priv->disp_thread[i].thread = NULL;
>> -		}
>> -
>>  		if (priv->event_thread[i].thread) {
>> 
> kthread_flush_worker(&priv->event_thread[i].worker);
>>  			kthread_stop(priv->event_thread[i].thread);
>> @@ -537,6 +534,22 @@ static int msm_drm_init(struct device *dev, 
>> struct
> drm_driver *drv)
>>  	ddev->mode_config.funcs = &mode_config_funcs;
>>  	ddev->mode_config.helper_private = &mode_config_helper_funcs;
>> 
>> +	/* initialize display thread */
>> +	kthread_init_worker(&priv->disp_thread.worker);
>> +	priv->disp_thread.dev = ddev;
>> +	priv->disp_thread.thread = kthread_run(kthread_worker_fn,
>> +					       &priv->disp_thread.worker,
>> +					       "disp_thread");
>> +	if (IS_ERR(priv->disp_thread.thread)) {
>> +		DRM_DEV_ERROR(dev, "failed to create crtc_commit
> kthread\n");
>> +		priv->disp_thread.thread = NULL;
>> +		goto err_msm_uninit;
>> +	}
>> +
>> +	ret = sched_setscheduler(priv->disp_thread.thread, SCHED_FIFO,
> &param);
>> +	if (ret)
>> +		pr_warn("display thread priority update failed: %d\n",
> ret);
>> +
>>  	/**
>>  	 * this priority was found during empiric testing to have
> appropriate
>>  	 * realtime scheduling to process display updates and interact
> with
>> @@ -544,27 +557,6 @@ static int msm_drm_init(struct device *dev, 
>> struct
> drm_driver *drv)
>>  	 */
>>  	param.sched_priority = 16;
>>  	for (i = 0; i < priv->num_crtcs; i++) {
>> -
>> -		/* initialize display thread */
>> -		priv->disp_thread[i].crtc_id = priv->crtcs[i]->base.id;
>> -		kthread_init_worker(&priv->disp_thread[i].worker);
>> -		priv->disp_thread[i].dev = ddev;
>> -		priv->disp_thread[i].thread =
>> -			kthread_run(kthread_worker_fn,
>> -				&priv->disp_thread[i].worker,
>> -				"crtc_commit:%d",
> priv->disp_thread[i].crtc_id);
>> -		if (IS_ERR(priv->disp_thread[i].thread)) {
>> -			DRM_DEV_ERROR(dev, "failed to create crtc_commit
> kthread\n");
>> -			priv->disp_thread[i].thread = NULL;
>> -			goto err_msm_uninit;
>> -		}
>> -
>> -		ret = sched_setscheduler(priv->disp_thread[i].thread,
>> -					 SCHED_FIFO, &param);
>> -		if (ret)
>> -			dev_warn(dev, "disp_thread set priority failed:
> %d\n",
>> -				 ret);
>> -
>>  		/* initialize event thread */
>>  		priv->event_thread[i].crtc_id = priv->crtcs[i]->base.id;
>>  		kthread_init_worker(&priv->event_thread[i].worker);
>> diff --git a/drivers/gpu/drm/msm/msm_drv.h
> b/drivers/gpu/drm/msm/msm_drv.h
>> index 9d11f32..e81b1fa 100644
>> --- a/drivers/gpu/drm/msm/msm_drv.h
>> +++ b/drivers/gpu/drm/msm/msm_drv.h
>> @@ -197,7 +197,7 @@ struct msm_drm_private {
>>  	unsigned int num_crtcs;
>>  	struct drm_crtc *crtcs[MAX_CRTCS];
>> 
>> -	struct msm_drm_thread disp_thread[MAX_CRTCS];
>> +	struct msm_drm_thread disp_thread;
>>  	struct msm_drm_thread event_thread[MAX_CRTCS];
>> 
>>  	unsigned int num_encoders;
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> Forum,
>> a Linux Foundation Collaborative Project
>> 
>> _______________________________________________
>> Freedreno mailing list
>> Freedreno@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/freedreno

-- 
Jeykumar S
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