linux-kernel - Re: [PATCH v9 14/15] drm/msm/atomic: Switch to vblank

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Date:   Fri, 3 Mar 2023 12:04:05 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Rob Clark <robdclark@...il.com>, dri-devel@...ts.freedesktop.org
Cc:     freedreno@...ts.freedesktop.org, Daniel Vetter <daniel@...ll.ch>,
        Christian König <ckoenig.leichtzumerken@...il.com>,
        Michel Dänzer <michel@...nzer.net>,
        Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Alex Deucher <alexander.deucher@....com>,
        Pekka Paalanen <ppaalanen@...il.com>,
        Simon Ser <contact@...rsion.fr>,
        Luben Tuikov <luben.tuikov@....com>,
        Rob Clark <robdclark@...omium.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Vinod Polimera <quic_vpolimer@...cinc.com>,
        Liu Shixin <liushixin2@...wei.com>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 14/15] drm/msm/atomic: Switch to vblank_start helper

On 03/03/2023 01:53, Rob Clark wrote:
> From: Rob Clark <robdclark@...omium.org>
> 
> Drop our custom thing and switch to drm_crtc_next_vblank_start() for
> calculating the time of the start of the next vblank period.
> 
> Signed-off-by: Rob Clark <robdclark@...omium.org>

It took me a while to dig into the differences between old and proposed 
paths. Looks correct to me.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 15 ---------------
>   drivers/gpu/drm/msm/msm_atomic.c        |  8 +++++---
>   drivers/gpu/drm/msm/msm_kms.h           |  8 --------
>   3 files changed, 5 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> index a683bd9b5a04..43996aecaf8c 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> @@ -411,20 +411,6 @@ static void dpu_kms_disable_commit(struct msm_kms *kms)
>   	pm_runtime_put_sync(&dpu_kms->pdev->dev);
>   }
>   
> -static ktime_t dpu_kms_vsync_time(struct msm_kms *kms, struct drm_crtc *crtc)
> -{
> -	struct drm_encoder *encoder;
> -
> -	drm_for_each_encoder_mask(encoder, crtc->dev, crtc->state->encoder_mask) {
> -		ktime_t vsync_time;
> -
> -		if (dpu_encoder_vsync_time(encoder, &vsync_time) == 0)
> -			return vsync_time;
> -	}
> -
> -	return ktime_get();
> -}
> -
>   static void dpu_kms_prepare_commit(struct msm_kms *kms,
>   		struct drm_atomic_state *state)
>   {
> @@ -953,7 +939,6 @@ static const struct msm_kms_funcs kms_funcs = {
>   	.irq             = dpu_core_irq,
>   	.enable_commit   = dpu_kms_enable_commit,
>   	.disable_commit  = dpu_kms_disable_commit,
> -	.vsync_time      = dpu_kms_vsync_time,
>   	.prepare_commit  = dpu_kms_prepare_commit,
>   	.flush_commit    = dpu_kms_flush_commit,
>   	.wait_flush      = dpu_kms_wait_flush,
> diff --git a/drivers/gpu/drm/msm/msm_atomic.c b/drivers/gpu/drm/msm/msm_atomic.c
> index 1686fbb611fd..c5e71c05f038 100644
> --- a/drivers/gpu/drm/msm/msm_atomic.c
> +++ b/drivers/gpu/drm/msm/msm_atomic.c
> @@ -186,8 +186,7 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state)
>   	struct msm_kms *kms = priv->kms;
>   	struct drm_crtc *async_crtc = NULL;
>   	unsigned crtc_mask = get_crtc_mask(state);
> -	bool async = kms->funcs->vsync_time &&
> -			can_do_async(state, &async_crtc);
> +	bool async = can_do_async(state, &async_crtc);
>   
>   	trace_msm_atomic_commit_tail_start(async, crtc_mask);
>   
> @@ -231,7 +230,9 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state)
>   
>   			kms->pending_crtc_mask |= crtc_mask;
>   
> -			vsync_time = kms->funcs->vsync_time(kms, async_crtc);
> +			if (drm_crtc_next_vblank_start(async_crtc, &vsync_time))
> +				goto fallback;
> +
>   			wakeup_time = ktime_sub(vsync_time, ms_to_ktime(1));
>   
>   			msm_hrtimer_queue_work(&timer->work, wakeup_time,
> @@ -253,6 +254,7 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state)
>   		return;
>   	}
>   
> +fallback:
>   	/*
>   	 * If there is any async flush pending on updated crtcs, fold
>   	 * them into the current flush.
> diff --git a/drivers/gpu/drm/msm/msm_kms.h b/drivers/gpu/drm/msm/msm_kms.h
> index f8ed7588928c..086a3f1ff956 100644
> --- a/drivers/gpu/drm/msm/msm_kms.h
> +++ b/drivers/gpu/drm/msm/msm_kms.h
> @@ -59,14 +59,6 @@ struct msm_kms_funcs {
>   	void (*enable_commit)(struct msm_kms *kms);
>   	void (*disable_commit)(struct msm_kms *kms);
>   
> -	/**
> -	 * If the kms backend supports async commit, it should implement
> -	 * this method to return the time of the next vsync.  This is
> -	 * used to determine a time slightly before vsync, for the async
> -	 * commit timer to run and complete an async commit.
> -	 */
> -	ktime_t (*vsync_time)(struct msm_kms *kms, struct drm_crtc *crtc);
> -
>   	/**
>   	 * Prepare for atomic commit.  This is called after any previous
>   	 * (async or otherwise) commit has completed.

-- 
With best wishes
Dmitry