Re: [PATCH 09/21] drm/i915: Stop mapping the scratch page into CPU space

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 03/06/16 17:08, Chris Wilson wrote:
> After the elimination of using the scratch page for Ironlake's
> breadcrumb, we no longer need to kmap the object. We therefore can move
> it into the high unmappable space and do not need to force the object to
> be coherent (i.e. snooped on !llc platforms).
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>   drivers/gpu/drm/i915/intel_ringbuffer.c | 40 +++++++++------------------------
>   drivers/gpu/drm/i915/intel_ringbuffer.h |  1 -
>   2 files changed, 11 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index bac496902c6d..106f40c52bb5 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -643,58 +643,40 @@ out:
>   	return ret;
>   }
>
> -void
> -intel_fini_pipe_control(struct intel_engine_cs *engine)
> +void intel_fini_pipe_control(struct intel_engine_cs *engine)
>   {
>   	if (engine->scratch.obj == NULL)
>   		return;
>
> -	if (INTEL_GEN(engine->i915) >= 5) {
> -		kunmap(sg_page(engine->scratch.obj->pages->sgl));
> -		i915_gem_object_ggtt_unpin(engine->scratch.obj);
> -	}
> -
> +	i915_gem_object_ggtt_unpin(engine->scratch.obj);
>   	drm_gem_object_unreference(&engine->scratch.obj->base);
>   	engine->scratch.obj = NULL;
>   }
>
> -int
> -intel_init_pipe_control(struct intel_engine_cs *engine)
> +int intel_init_pipe_control(struct intel_engine_cs *engine)
>   {
> +	struct drm_i915_gem_object *obj;
>   	int ret;
>
>   	WARN_ON(engine->scratch.obj);
>
> -	engine->scratch.obj = i915_gem_object_create(engine->i915->dev, 4096);
> -	if (IS_ERR(engine->scratch.obj)) {
> -		DRM_ERROR("Failed to allocate seqno page\n");
> -		ret = PTR_ERR(engine->scratch.obj);
> -		engine->scratch.obj = NULL;
> +	obj = i915_gem_object_create(engine->i915->dev, 4096);
> +	if (IS_ERR(obj)) {
> +		DRM_ERROR("Failed to allocate scratch page\n");
> +		ret = PTR_ERR(obj);
>   		goto err;
>   	}
>
> -	ret = i915_gem_object_set_cache_level(engine->scratch.obj,
> -					      I915_CACHE_LLC);
> +	ret = i915_gem_obj_ggtt_pin(obj, 4096, PIN_HIGH);
>   	if (ret)
>   		goto err_unref;
>
> -	ret = i915_gem_obj_ggtt_pin(engine->scratch.obj, 4096, 0);
> -	if (ret)
> -		goto err_unref;
> -
> -	engine->scratch.gtt_offset = i915_gem_obj_ggtt_offset(engine->scratch.obj);
> -	engine->scratch.cpu_page = kmap(sg_page(engine->scratch.obj->pages->sgl));
> -	if (engine->scratch.cpu_page == NULL) {
> -		ret = -ENOMEM;
> -		goto err_unpin;
> -	}
> -
> +	engine->scratch.obj = obj;
> +	engine->scratch.gtt_offset = i915_gem_obj_ggtt_offset(obj);
>   	DRM_DEBUG_DRIVER("%s pipe control offset: 0x%08x\n",
>   			 engine->name, engine->scratch.gtt_offset);
>   	return 0;
>
> -err_unpin:
> -	i915_gem_object_ggtt_unpin(engine->scratch.obj);
>   err_unref:
>   	drm_gem_object_unreference(&engine->scratch.obj->base);
>   err:
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
> index 785c9e5312ff..4b2f19decb30 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> @@ -338,7 +338,6 @@ struct intel_engine_cs {
>   	struct {
>   		struct drm_i915_gem_object *obj;
>   		u32 gtt_offset;
> -		volatile u32 *cpu_page;
>   	} scratch;
>
>   	bool needs_cmd_parser;
>

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko

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