linux-kernel - Re: [PATCH v5 3/4] drm/fence: add fence timeline to drm

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Message-ID: <20161021125446.GE20761@phenom.ffwll.local>
Date:   Fri, 21 Oct 2016 14:54:46 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Gustavo Padovan <gustavo@...ovan.org>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Daniel Stone <daniels@...labora.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Rob Clark <robdclark@...il.com>,
        Greg Hackmann <ghackmann@...gle.com>,
        John Harrison <John.C.Harrison@...el.com>,
        laurent.pinchart@...asonboard.com, seanpaul@...gle.com,
        marcheu@...gle.com, m.chehab@...sung.com,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Gustavo Padovan <gustavo.padovan@...labora.co.uk>
Subject: Re: [PATCH v5 3/4] drm/fence: add fence timeline to drm_crtc

On Thu, Oct 20, 2016 at 12:50:04PM -0200, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
> 
> Create one timeline context for each CRTC to be able to handle out-fences
> and signal them. It adds a few members to struct drm_crtc: fence_context,
> where we store the context we get from fence_context_alloc(), the
> fence seqno and the fence lock, that we pass in fence_init() to be
> used by the fence.
> 
> v2: Comment by Daniel Stone:
> 	- add BUG_ON() to fence_to_crtc() macro
> 
> v3: Comment by Ville Syrjälä
> 	- Use more meaningful name as crtc timeline name
> 
> Signed-off-by: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
> ---
>  drivers/gpu/drm/drm_crtc.c | 31 +++++++++++++++++++++++++++++++
>  include/drm/drm_crtc.h     | 19 +++++++++++++++++++
>  2 files changed, 50 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index fcb6453..b99090f 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -165,6 +165,32 @@ static void drm_crtc_crc_fini(struct drm_crtc *crtc)
>  #endif
>  }
>  
> +static const char *drm_crtc_fence_get_driver_name(struct fence *fence)
> +{
> +	struct drm_crtc *crtc = fence_to_crtc(fence);
> +
> +	return crtc->dev->driver->name;
> +}
> +
> +static const char *drm_crtc_fence_get_timeline_name(struct fence *fence)
> +{
> +	struct drm_crtc *crtc = fence_to_crtc(fence);
> +
> +	return crtc->timeline_name;
> +}
> +
> +static bool drm_crtc_fence_enable_signaling(struct fence *fence)
> +{
> +	return true;
> +}
> +
> +const struct fence_ops drm_crtc_fence_ops = {
> +	.get_driver_name = drm_crtc_fence_get_driver_name,
> +	.get_timeline_name = drm_crtc_fence_get_timeline_name,
> +	.enable_signaling = drm_crtc_fence_enable_signaling,
> +	.wait = fence_default_wait,
> +};
> +
>  /**
>   * drm_crtc_init_with_planes - Initialise a new CRTC object with
>   *    specified primary and cursor planes.
> @@ -222,6 +248,11 @@ int drm_crtc_init_with_planes(struct drm_device *dev, struct drm_crtc *crtc,
>  		return -ENOMEM;
>  	}
>  
> +	crtc->fence_context = fence_context_alloc(1);
> +	spin_lock_init(&crtc->fence_lock);
> +	snprintf(crtc->timeline_name, sizeof(crtc->timeline_name),
> +		 "drm_crtc-%d", crtc->base.id);
> +
>  	crtc->base.properties = &crtc->properties;
>  
>  	list_add_tail(&crtc->head, &config->crtc_list);
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 279132e..657a33a 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -32,6 +32,8 @@
>  #include <linux/fb.h>
>  #include <linux/hdmi.h>
>  #include <linux/media-bus-format.h>
> +#include <linux/srcu.h>
> +#include <linux/fence.h>
>  #include <uapi/drm/drm_mode.h>
>  #include <uapi/drm/drm_fourcc.h>
>  #include <drm/drm_modeset_lock.h>
> @@ -618,6 +620,9 @@ struct drm_crtc_funcs {
>   * @gamma_store: gamma ramp values
>   * @helper_private: mid-layer private data
>   * @properties: property tracking for this CRTC
> + * @fence_context: context for fence signalling
> + * @fence_lock: fence lock for the fence context
> + * @fence_seqno: seqno variable to create fences

For new stuff I much prefer in-line kerneldoc with structures, keeps the
comments much closer to the code ...
>   *
>   * Each CRTC may have one or more connectors associated with it.  This structure
>   * allows the CRTC to be controlled.
> @@ -726,8 +731,22 @@ struct drm_crtc {
>  	 */
>  	struct drm_crtc_crc crc;
>  #endif
> +
> +	/* fence timelines info for DRM out-fences */

... and avoids duplicated comments like this one here.

Otherwise lgtm.
-Daniel

> +	unsigned int fence_context;
> +	spinlock_t fence_lock;
> +	unsigned long fence_seqno;
> +	char timeline_name[32];
>  };
>  
> +extern const struct fence_ops drm_crtc_fence_ops;
> +
> +static inline struct drm_crtc *fence_to_crtc(struct fence *fence)
> +{
> +	BUG_ON(fence->ops != &drm_crtc_fence_ops);
> +	return container_of(fence->lock, struct drm_crtc, fence_lock);
> +}
> +
>  /**
>   * struct drm_mode_set - new values for a CRTC config change
>   * @fb: framebuffer to use for new config
> -- 
> 2.5.5
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch