linux-kernel - Re: [PATCH v8 2/3] drm: writeback: Add out-fences for writeback connectors

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Message-ID: <87a7ssu91a.fsf@anholt.net>
Date:   Mon, 21 May 2018 12:02:25 -0700
From:   Eric Anholt <eric@...olt.net>
To:     Liviu Dudau <Liviu.Dudau@....com>,
        Gustavo Padovan <gustavo@...ovan.org>
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Sean Paul <seanpaul@...omium.org>,
        Jonathan Corbet <corbet@....net>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        David Airlie <airlied@...ux.ie>,
        Brian Starkey <brian.starkey@....com>,
        Alexandru-Cosmin Gheorghe <alexandru-cosmin.gheorghe@....com>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Daniel Stone <daniels@...labora.com>,
        Mihail Atanassov <mihail.atanassov@....com>,
        Liviu Dudau <liviu.dudau@....com>
Subject: Re: [PATCH v8 2/3] drm: writeback: Add out-fences for writeback connectors

Liviu Dudau <Liviu.Dudau@....com> writes:

> From: Brian Starkey <brian.starkey@....com>
>
> Add the WRITEBACK_OUT_FENCE_PTR property to writeback connectors, to
> enable userspace to get a fence which will signal once the writeback is
> complete. It is not allowed to request an out-fence without a
> framebuffer attached to the connector.
>
> A timeline is added to drm_writeback_connector for use by the writeback
> out-fences.


> diff --git a/include/drm/drm_writeback.h b/include/drm/drm_writeback.h
> index cf3a28676006a..6a7462c1821ad 100644
> --- a/include/drm/drm_writeback.h
> +++ b/include/drm/drm_writeback.h
> @@ -49,6 +49,32 @@ struct drm_writeback_connector {
>  	 * drm_writeback_signal_completion()
>  	 */
>  	struct list_head job_queue;
> +
> +	/**
> +	 * @fence_context:
> +	 *
> +	 * timeline context used for fence operations.
> +	 */
> +	unsigned int fence_context;
> +	/**
> +	 * @fence_lock:
> +	 *
> +	 * spinlock to protect the fences in the fence_context.
> +	 */
> +	spinlock_t fence_lock;
> +	/**
> +	 * @fence_seqno:
> +	 *
> +	 * Seqno variable used as monotonic counter for the fences
> +	 * created on the connector's timeline.
> +	 */
> +	unsigned long fence_seqno;
> +	/**
> +	 * @timeline_name:
> +	 *
> +	 * The name of the connector's fence timeline.
> +	 */
> +	char timeline_name[32];
>  };
>  
>  struct drm_writeback_job {
> @@ -59,12 +85,14 @@ struct drm_writeback_job {
>  	 * framebuffer reference to a workqueue.
>  	 */
>  	struct work_struct cleanup_work;
> +
>  	/**
>  	 * @list_entry:
>  	 *
>  	 * List item for the connector's @job_queue
>  	 */
>  	struct list_head list_entry;
> +
>  	/**
>  	 * @fb:
>  	 *

Move this hunk into patch 1?

Other than that, the series is:

Reviewed-by: Eric Anholt <eric@...olt.net>

It's pretty clean and makes sense to me.  I only had some questions
about the job_queue, which seems superfluous if we aren't supporting
firing off a new writeback while an old one is outstanding (and maybe we
should throw an error in that case).  Still, I think this is ready to land.

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