linux-kernel - Re: [RFC 5/8] drm/fence: add fence to drm_pending

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Message-ID: <20160415080948.GS2510@phenom.ffwll.local>
Date:	Fri, 15 Apr 2016 10:09:48 +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>,
	Arve Hjønnevåg <arve@...roid.com>,
	Riley Andrews <riandrews@...roid.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,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Gustavo Padovan <gustavo.padovan@...labora.co.uk>
Subject: Re: [RFC 5/8] drm/fence: add fence to drm_pending_event

On Thu, Apr 14, 2016 at 06:29:38PM -0700, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
> 
> Now a drm_pending_event can either send a real drm_event or signal a
> fence, or both. It allow us to signal via fences when the buffer is
> displayed on the screen. Which in turn means that the previous buffer
> is not in use anymore and can be freed or sent back to another driver
> for processing.
> 
> Signed-off-by: Gustavo Padovan <gustavo.padovan@...labora.co.uk>

Do you have atomic igt testcase that exercise all the combinations of
drm_event and in/out-fences and make sure it all keeps working? Tomeu
already converted that over to be a generic testcase.

> ---
>  drivers/gpu/drm/drm_atomic.c | 19 +++++++++++++------
>  drivers/gpu/drm/drm_fops.c   |  5 +++--
>  drivers/gpu/drm/drm_irq.c    |  7 +++++++
>  include/drm/drmP.h           |  1 +
>  4 files changed, 24 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 6702502..0b95526 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1431,7 +1431,8 @@ EXPORT_SYMBOL(drm_atomic_async_commit);
>   */
>  
>  static struct drm_pending_vblank_event *create_vblank_event(
> -		struct drm_device *dev, struct drm_file *file_priv, uint64_t user_data)
> +		struct drm_device *dev, struct drm_file *file_priv,
> +		struct fence *fence, uint64_t user_data)
>  {
>  	struct drm_pending_vblank_event *e = NULL;
>  	int ret;
> @@ -1444,12 +1445,17 @@ static struct drm_pending_vblank_event *create_vblank_event(
>  	e->event.base.length = sizeof(e->event);
>  	e->event.user_data = user_data;
>  
> -	ret = drm_event_reserve_init(dev, file_priv, &e->base, &e->event.base);
> -	if (ret) {
> -		kfree(e);
> -		return NULL;
> +	if (file_priv) {
> +		ret = drm_event_reserve_init(dev, file_priv, &e->base,
> +					     &e->event.base);
> +		if (ret) {
> +			kfree(e);
> +			return NULL;
> +		}
>  	}
>  
> +	e->base.fence = fence;
> +
>  	return e;
>  }
>  
> @@ -1676,7 +1682,8 @@ retry:
>  		for_each_crtc_in_state(state, crtc, crtc_state, i) {
>  			struct drm_pending_vblank_event *e;
>  
> -			e = create_vblank_event(dev, file_priv, arg->user_data);
> +			e = create_vblank_event(dev, file_priv, NULL,
> +						arg->user_data);
>  			if (!e) {
>  				ret = -ENOMEM;
>  				goto out;
> diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
> index aeef58e..38def49 100644
> --- a/drivers/gpu/drm/drm_fops.c
> +++ b/drivers/gpu/drm/drm_fops.c
> @@ -801,8 +801,9 @@ void drm_send_event_locked(struct drm_device *dev, struct drm_pending_event *e)
>  {
>  	assert_spin_locked(&dev->event_lock);
>  
> -	if (!e->file_priv) {
> -		e->destroy(e);
> +	if (!e->file_priv || !e->event) {

This would be a bug: e->file_priv != NULL iff e->event != NULL. How did
this happen?

> +		if (e->destroy)
> +			e->destroy(e);
>  		return;
>  	}
>  
> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> index 3c1a6f1..0c5d7cb 100644
> --- a/drivers/gpu/drm/drm_irq.c
> +++ b/drivers/gpu/drm/drm_irq.c
> @@ -41,6 +41,7 @@
>  
>  #include <linux/vgaarb.h>
>  #include <linux/export.h>
> +#include <linux/fence.h>
>  
>  /* Access macro for slots in vblank timestamp ringbuffer. */
>  #define vblanktimestamp(dev, pipe, count) \
> @@ -1124,6 +1125,12 @@ void drm_send_vblank_event(struct drm_device *dev, unsigned int pipe,
>  		now = get_drm_timestamp();
>  	}
>  	e->pipe = pipe;
> +
> +	if (e->base.fence) {
> +		fence_signal(e->base.fence);
> +		fence_put(e->base.fence);
> +	}

I'd put this into drm_send_event_locked even. In case we send out fences
for other events too (e.g. exynos uses drm_event for rendering ...).
-Daniel

> +
>  	send_vblank_event(dev, e, seq, &now);
>  }
>  EXPORT_SYMBOL(drm_send_vblank_event);
> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
> index 3c8422c..8f83c2a 100644
> --- a/include/drm/drmP.h
> +++ b/include/drm/drmP.h
> @@ -282,6 +282,7 @@ struct drm_ioctl_desc {
>  /* Event queued up for userspace to read */
>  struct drm_pending_event {
>  	struct drm_event *event;
> +	struct fence *fence;
>  	struct list_head link;
>  	struct list_head pending_link;
>  	struct drm_file *file_priv;
> -- 
> 2.5.5
> 

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