Re: [PATCH] drm/i915: Refactor the wait_rendering completion into a common routine

[Daniel Vetter <daniel@ffwll.ch>]

On Sat, Jun 29, 2013 at 10:05:26PM +0100, Chris Wilson wrote:
> Harmonise the completion logic between the non-blocking and normal
> wait_rendering paths, and move that logic into a common function.
> 
> In the process, we note that the last_write_seqno is by definition the
> earlier of the two read/write seqnos and so all successful waits will
> have passed the last_write_seqno. Therefore we can unconditionally clear
> the write seqno and its domains in the completion logic.
> 
> v2: Add the missing ring parameter, because sometimes it is good to have
> things compile.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Queued for -next, thanks for the patch.
-Daniel
> ---
>  drivers/gpu/drm/i915/i915_gem.c | 48 ++++++++++++++++++++---------------------
>  1 file changed, 23 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 8e9e9d7..7c9ed3a 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1087,6 +1087,25 @@ i915_wait_seqno(struct intel_ring_buffer *ring, uint32_t seqno)
>  			    interruptible, NULL);
>  }
>  
> +static int
> +i915_gem_object_wait_rendering__tail(struct drm_i915_gem_object *obj,
> +				     struct intel_ring_buffer *ring)
> +{
> +	i915_gem_retire_requests_ring(ring);
> +
> +	/* Manually manage the write flush as we may have not yet
> +	 * retired the buffer.
> +	 *
> +	 * Note that the last_write_seqno is always the earlier of
> +	 * the two (read/write) seqno, so if we haved successfully waited,
> +	 * we know we have passed the last write.
> +	 */
> +	obj->last_write_seqno = 0;
> +	obj->base.write_domain &= ~I915_GEM_GPU_DOMAINS;
> +
> +	return 0;
> +}
> +
>  /**
>   * Ensures that all rendering to the object has completed and the object is
>   * safe to unbind from the GTT or access from the CPU.
> @@ -1107,18 +1126,7 @@ i915_gem_object_wait_rendering(struct drm_i915_gem_object *obj,
>  	if (ret)
>  		return ret;
>  
> -	i915_gem_retire_requests_ring(ring);
> -
> -	/* Manually manage the write flush as we may have not yet
> -	 * retired the buffer.
> -	 */
> -	if (obj->last_write_seqno &&
> -	    i915_seqno_passed(seqno, obj->last_write_seqno)) {
> -		obj->last_write_seqno = 0;
> -		obj->base.write_domain &= ~I915_GEM_GPU_DOMAINS;
> -	}
> -
> -	return 0;
> +	return i915_gem_object_wait_rendering__tail(obj, ring);
>  }
>  
>  /* A nonblocking variant of the above wait. This is a highly dangerous routine
> @@ -1154,20 +1162,10 @@ i915_gem_object_wait_rendering__nonblocking(struct drm_i915_gem_object *obj,
>  	mutex_unlock(&dev->struct_mutex);
>  	ret = __wait_seqno(ring, seqno, reset_counter, true, NULL);
>  	mutex_lock(&dev->struct_mutex);
> +	if (ret)
> +		return ret;
>  
> -	i915_gem_retire_requests_ring(ring);
> -
> -	/* Manually manage the write flush as we may have not yet
> -	 * retired the buffer.
> -	 */
> -	if (ret == 0 &&
> -	    obj->last_write_seqno &&
> -	    i915_seqno_passed(seqno, obj->last_write_seqno)) {
> -		obj->last_write_seqno = 0;
> -		obj->base.write_domain &= ~I915_GEM_GPU_DOMAINS;
> -	}
> -
> -	return ret;
> +	return i915_gem_object_wait_rendering__tail(obj, ring);
>  }
>  
>  /**
> -- 
> 1.8.3.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch