[PATCH 2/3] drm: Skip the waitqueue setup for vblank queries

[Daniel Vetter]

On Wed, Mar 15, 2017 at 08:40:26PM +0000, Chris Wilson wrote:
> Avoid adding to the waitqueue and reprobing the current vblank if the
> caller is only querying the current vblank sequence and timestamp, where
> we know that the wait would return immediately.
> 
> v2: Add CRTC identifier to debug messages
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Michel Dänzer <michel at daenzer.net>
> Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> Cc: Dave Airlie <airlied at redhat.com>,
> Cc: Mario Kleiner <mario.kleiner.de at gmail.com>
> Reviewed-by: Michel Dänzer <michel at daenzer.net>
> Reviewed-and-tested-by: Mario Kleiner <mario.kleiner.de at gmail.com>

Merged the first two from this series, thanks.
-Daniel

> ---
>  drivers/gpu/drm/drm_irq.c | 24 +++++++++++++-----------
>  1 file changed, 13 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> index e64b05ea95ea..53a526c7b24d 100644
> --- a/drivers/gpu/drm/drm_irq.c
> +++ b/drivers/gpu/drm/drm_irq.c
> @@ -1610,7 +1610,7 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
>  
>  	ret = drm_vblank_get(dev, pipe);
>  	if (ret) {
> -		DRM_DEBUG("failed to acquire vblank counter, %d\n", ret);
> +		DRM_DEBUG("crtc %d failed to acquire vblank counter, %d\n", pipe, ret);
>  		return ret;
>  	}
>  	seq = drm_vblank_count(dev, pipe);
> @@ -1638,13 +1638,15 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
>  		return drm_queue_vblank_event(dev, pipe, vblwait, file_priv);
>  	}
>  
> -	DRM_DEBUG("waiting on vblank count %u, crtc %u\n",
> -		  vblwait->request.sequence, pipe);
> -	DRM_WAIT_ON(ret, vblank->queue, 3 * HZ,
> -		    (((drm_vblank_count(dev, pipe) -
> -		       vblwait->request.sequence) <= (1 << 23)) ||
> -		     !vblank->enabled ||
> -		     !dev->irq_enabled));
> +	if (vblwait->request.sequence != seq) {
> +		DRM_DEBUG("waiting on vblank count %u, crtc %u\n",
> +			  vblwait->request.sequence, pipe);
> +		DRM_WAIT_ON(ret, vblank->queue, 3 * HZ,
> +			    (((drm_vblank_count(dev, pipe) -
> +			       vblwait->request.sequence) <= (1 << 23)) ||
> +			     !vblank->enabled ||
> +			     !dev->irq_enabled));
> +	}
>  
>  	if (ret != -EINTR) {
>  		struct timeval now;
> @@ -1653,10 +1655,10 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
>  		vblwait->reply.tval_sec = now.tv_sec;
>  		vblwait->reply.tval_usec = now.tv_usec;
>  
> -		DRM_DEBUG("returning %u to client\n",
> -			  vblwait->reply.sequence);
> +		DRM_DEBUG("crtc %d returning %u to client\n",
> +			  pipe, vblwait->reply.sequence);
>  	} else {
> -		DRM_DEBUG("vblank wait interrupted by signal\n");
> +		DRM_DEBUG("crtc %d vblank wait interrupted by signal\n", pipe);
>  	}
>  
>  done:
> -- 
> 2.11.0
> 

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