linux-kernel - Re: [PATCH] drm/vc4: Return -EBUSY if there's already a pending flip event.

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Date:	Tue, 3 May 2016 09:11:34 +0200
From:	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
To:	robert.foss@...labora.com, daniel.vetter@...ll.ch,
	airlied@...ux.ie, eric@...olt.net, aniel.vetter@...ll.ch,
	fengguang.wu@...el.com, julia.lawall@...6.fr,
	alexander.deucher@....com, daniels@...labora.com,
	derekf@....samsung.com, varadgautam@...il.com
Cc:	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/vc4: Return -EBUSY if there's already a pending flip
 event.

Op 02-05-16 om 21:25 schreef robert.foss@...labora.com:
> From: Robert Foss <robert.foss@...labora.com>
>
> As per the docs, atomic_commit should return -EBUSY "if an asycnhronous
> update is requested and there is an earlier update pending".
>
> Signed-off-by: Robert Foss <robert.foss@...labora.com>
> ---
>  drivers/gpu/drm/vc4/vc4_crtc.c |  6 ++++++
>  drivers/gpu/drm/vc4/vc4_drv.h  |  1 +
>  drivers/gpu/drm/vc4/vc4_kms.c  | 20 ++++++++++++++++++--
>  3 files changed, 25 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
> index 355ee4b..43193a3 100644
> --- a/drivers/gpu/drm/vc4/vc4_crtc.c
> +++ b/drivers/gpu/drm/vc4/vc4_crtc.c
> @@ -802,3 +802,9 @@ struct platform_driver vc4_crtc_driver = {
>  		.of_match_table = vc4_crtc_dt_match,
>  	},
>  };
> +
> +bool vc4_crtc_has_pending_event(struct drm_crtc *crtc)
> +{
> +	assert_spin_locked(&crtc->dev->event_lock);
> +	return to_vc4_crtc(crtc)->event;
> +}
> diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
> index fa2ad15..54c1fb5 100644
> --- a/drivers/gpu/drm/vc4/vc4_drv.h
> +++ b/drivers/gpu/drm/vc4/vc4_drv.h
> @@ -414,6 +414,7 @@ extern struct platform_driver vc4_crtc_driver;
>  int vc4_enable_vblank(struct drm_device *dev, unsigned int crtc_id);
>  void vc4_disable_vblank(struct drm_device *dev, unsigned int crtc_id);
>  int vc4_crtc_debugfs_regs(struct seq_file *m, void *arg);
> +bool vc4_crtc_has_pending_event(struct drm_crtc *crtc);
>  
>  /* vc4_debugfs.c */
>  int vc4_debugfs_init(struct drm_minor *minor);
> diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
> index 4718ae5..dc157a1e 100644
> --- a/drivers/gpu/drm/vc4/vc4_kms.c
> +++ b/drivers/gpu/drm/vc4/vc4_kms.c
> @@ -107,10 +107,26 @@ static int vc4_atomic_commit(struct drm_device *dev,
>  			     bool async)
>  {
>  	struct vc4_dev *vc4 = to_vc4_dev(dev);
> -	int ret;
> -	int i;
>  	uint64_t wait_seqno = 0;
>  	struct vc4_commit *c;
> +	struct drm_crtc_state *crtc_state;
> +	struct drm_crtc *crtc;
> +	unsigned long flags;
> +	int i, ret;
> +
> +	if (async) {
> +		for_each_crtc_in_state(state, crtc, crtc_state, i) {
> +
> +			spin_lock_irqsave(&dev->event_lock, flags);
> +
> +			if (crtc->state->event || 
^What's this check for? How can this even happen if you remove the event from the crtc state in atomic_flush?

~Maarten