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

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Date:	Thu, 31 Mar 2016 09:25:43 +0800
From:	Mark yao <mark.yao@...k-chips.com>
To:	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	linux-kernel@...r.kernel.org
CC:	David Airlie <airlied@...ux.ie>, Heiko Stuebner <heiko@...ech.de>,
	dri-devel@...ts.freedesktop.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH] drm/rockchip: Return -EBUSY if there's already a pending
 flip event

On 2016年03月30日 21:48, Tomeu Vizoso wrote:
> As per the docs, atomic_commit should return -EBUSY "if an asycnhronous
> updated is requested and there is an earlier updated pending".
>
> Also wait for the pending event to complete when a sync update is
> requested.
>
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
> ---
>   drivers/gpu/drm/rockchip/rockchip_drm_drv.h |  1 +
>   drivers/gpu/drm/rockchip/rockchip_drm_fb.c  | 14 +++++++++++++-
>   drivers/gpu/drm/rockchip/rockchip_drm_vop.c |  6 ++++++
>   3 files changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.h b/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
> index 3529f692edb8..37952eefd33d 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
> @@ -69,6 +69,7 @@ int rockchip_register_crtc_funcs(struct drm_crtc *crtc,
>   void rockchip_unregister_crtc_funcs(struct drm_crtc *crtc);
>   int rockchip_drm_crtc_mode_config(struct drm_crtc *crtc, int connector_type,
>   				  int out_mode);
> +bool rockchip_drm_crtc_has_pending_event(struct drm_crtc *crtc);
>   int rockchip_drm_dma_attach_device(struct drm_device *drm_dev,
>   				   struct device *dev);
>   void rockchip_drm_dma_detach_device(struct drm_device *drm_dev,
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> index 3b8f652698f8..028fd2f8f47b 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> @@ -280,7 +280,19 @@ int rockchip_drm_atomic_commit(struct drm_device *dev,
>   {
>   	struct rockchip_drm_private *private = dev->dev_private;
>   	struct rockchip_atomic_commit *commit = &private->commit;
> -	int ret;
> +	struct drm_crtc_state *crtc_state;
> +	struct drm_crtc *crtc;
> +	int i, ret;
> +
> +	for_each_crtc_in_state(state, crtc, crtc_state, i) {
> +		if (crtc->state->event ||
> +		    rockchip_drm_crtc_has_pending_event(crtc)) {
> +			if (async)
> +				return -EBUSY;
> +			else
> +				rockchip_crtc_wait_for_update(crtc);

> +		}
> +	}
>   
>   	ret = drm_atomic_helper_prepare_planes(dev, state);
>   	if (ret)
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> index e2118e62345b..5240bc8fe088 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> @@ -848,6 +848,12 @@ int rockchip_drm_crtc_mode_config(struct drm_crtc *crtc,
>   }
>   EXPORT_SYMBOL_GPL(rockchip_drm_crtc_mode_config);
>   
> +bool rockchip_drm_crtc_has_pending_event(struct drm_crtc *crtc)
> +{
> +	return to_vop(crtc)->event;
> +}
> +EXPORT_SYMBOL_GPL(rockchip_drm_crtc_has_pending_event);
> +

No need to do EXPORT_SYMBOL_GPL, rockchip_drm_vop.c and rockchip_drm_fb.c will build into same object.


>   static int vop_crtc_enable_vblank(struct drm_crtc *crtc)
>   {
>   	struct vop *vop = to_vop(crtc);
Hi Tomeu

Since rockchip atomic async use "serialize outstanding asynchronous 
commits", async commit will wait on "flush_work(&commit->work);" to 
ensure last pending event is done, so vop->event should be NULL after 
flush. if not, it should be a BUG.

Anyway, serialize async commits is not a good way, but I don't think 
your patch is better way.

I think maybe we can check the "commit->work" status(finish or running) 
to judge return BUSY or not, instead of flush it.

Thanks.

-- 
Ｍark Yao