[Intel-gfx] [PATCH 7/7] drm/i915/vlv: Use Blitter Engine to clear out contents of Stolen frame buffers

[Daniel Vetter]

On Thu, Jan 09, 2014 at 11:01:56AM +0530, akash.goel at intel.com wrote:
> From: Akash Goel <akash.goel at intel.com>
> 
> On VLV, to clear out the contents of Frame buffers allocated from
> stolen area, Blitter engine is being used, to avoid the waste of
> CPU cycles in doing a sw based memset.
> 
> Signed-off-by: Akash Goel <akash.goel at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem_stolen.c | 87 ++++++++++++++++++++++++++++++++--
>  1 file changed, 84 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
> index 253a39a..10237c8 100644
> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
> @@ -371,7 +371,84 @@ i915_gem_object_create_stolen(struct drm_device *dev, u32 size)
>  	return NULL;
>  }
>  
> -static void i915_memset_stolen_obj(struct drm_i915_gem_object *obj)
> +static int i915_add_clear_obj_cmd(struct drm_i915_gem_object *obj)
> +{
> +	struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
> +	struct intel_ring_buffer *ring = &dev_priv->ring[BCS];

Pre-gen6 has the blitter on the RCS ring.

> +	uint32_t obj_height = (obj->base.size / obj->stride);

obj->stride is 0 for untiled buffers, so for more robustness I'd just use
4096 (page size) as stride. For even more robustness I think we should
have checks here to make sure that we don't overflow blitter hw limits
here.

> +	u32 offset = i915_gem_obj_ggtt_offset(obj);
> +	int ret;
> +
> +#define	COLOR_BLIT_OP		((0x2 << 29) | (0x40 << 22) | (0x3 << 20) | 0x3)
> +#define	COLOR_BLIT_OP_DW1	((0x3 << 24) | (0xF0 << 16) | (obj->stride))
> +#define	COLOR_BLIT_OP_DW2	((obj_height << 16) | (obj->stride))
> +#define	COLOR_BLIT_OP_DW3	(offset)
> +#define	COLOR_BLIT_OP_DW4	(0x0)

These #defines imo don't help readability, everywhere else
(kernel/userspace) we construct the cmd dwords in-line in the
OUT_BATCH/intel_ring_emit calls. Also please use the existing XY_ blt cmd
#defines in i915_reg.h.
- Daniel

> +
> +	ret = intel_ring_begin(ring, 6);
> +	if (ret)
> +		return ret;
> +	intel_ring_emit(ring, COLOR_BLIT_OP);
> +	intel_ring_emit(ring, COLOR_BLIT_OP_DW1);
> +	intel_ring_emit(ring, COLOR_BLIT_OP_DW2);
> +	intel_ring_emit(ring, COLOR_BLIT_OP_DW3);
> +	intel_ring_emit(ring, COLOR_BLIT_OP_DW4);
> +	intel_ring_emit(ring, MI_NOOP);
> +	intel_ring_advance(ring);
> +
> +	return 0;
> +}
> +
> +static int i915_memset_stolen_obj_hw(struct drm_i915_gem_object *obj)
> +{
> +	struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
> +	struct intel_ring_buffer *ring = &dev_priv->ring[BCS];
> +	unsigned alignment = 0;
> +	bool map_and_fenceable =  true;
> +	bool nonblocking = false;
> +	u32 seqno;
> +	int ret;
> +
> +	ret = i915_gem_obj_ggtt_pin(obj, alignment, map_and_fenceable,
> +		nonblocking);
> +	if (ret) {
> +		DRM_ERROR("Mapping of User FB to GTT failed\n");
> +		return ret;
> +	}
> +
> +	/* Adding commands to the blitter ring to
> +	 * clear out the contents of the buffer object
> +	 */
> +	ret = i915_add_clear_obj_cmd(obj);
> +	if (ret) {
> +		DRM_ERROR("couldn't add commands in blitter ring\n");
> +		i915_gem_object_ggtt_unpin(obj);
> +		return ret;
> +	}
> +
> +	seqno = intel_ring_get_seqno(ring);
> +
> +	/* Object now in render domain */
> +	obj->base.read_domains = I915_GEM_DOMAIN_RENDER;
> +	obj->base.write_domain = I915_GEM_DOMAIN_RENDER;
> +
> +	i915_vma_move_to_active(i915_gem_obj_to_ggtt(obj), ring);
> +
> +	obj->dirty = 1;
> +	obj->last_write_seqno = seqno;
> +
> +	/* Unconditionally force add_request to emit a full flush. */
> +	ring->gpu_caches_dirty = true;
> +
> +	/* Add a breadcrumb for the completion of the clear request */
> +	(void)i915_add_request(ring, NULL);
> +
> +	i915_gem_object_ggtt_unpin(obj);
> +
> +	return 0;
> +}
> +
> +static void i915_memset_stolen_obj_sw(struct drm_i915_gem_object *obj)
>  {
>  	int ret;
>  	char __iomem *base;
> @@ -490,9 +567,13 @@ i915_gem_object_move_to_stolen(struct drm_i915_gem_object *obj)
>  	obj->cache_level = HAS_LLC(dev) ? I915_CACHE_LLC : I915_CACHE_NONE;
>  
>  	/* Zero-out the contents of the stolen object, otherwise we observe
> -	 * corruptions in the display.
> +	 * corruptions in the display. First try using the blitter engine
> +	 * to clear the buffer contents
>  	 */
> -	i915_memset_stolen_obj(obj);
> +	ret = i915_memset_stolen_obj_hw(obj);
> +	/* fallback to Sw based memset if Hw memset fails */
> +	if (ret)
> +		i915_memset_stolen_obj_sw(obj);
>  	return;
>  
>  cleanup:
> -- 
> 1.8.5.2
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch