[Intel-gfx] [PATCH 4/8] drm/i915: Before accessing an object via the cpu, flush GTT writes

[Joonas Lahtinen]

On to, 2016-06-09 at 12:29 +0100, Chris Wilson wrote:
> If we want to read the pages directly via the CPU, we have to be sure
> that we have to flush the writes via the GTT (as the CPU can not see
> the address aliasing).
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>

Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

> ---
>  drivers/gpu/drm/i915/i915_gem.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index c6d06cb21191..18b4a684ddde 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -571,6 +571,8 @@ int i915_gem_obj_prepare_shmem_read(struct drm_i915_gem_object *obj,
>  	if ((obj->ops->flags & I915_GEM_OBJECT_HAS_STRUCT_PAGE) == 0)
>  		return -EINVAL;
>  
> +	i915_gem_object_flush_gtt_write_domain(obj);
> +
>  	if (!(obj->base.read_domains & I915_GEM_DOMAIN_CPU)) {
>  		ret = i915_gem_object_wait_rendering(obj, true);
>  		if (ret)
> @@ -611,6 +613,8 @@ int i915_gem_obj_prepare_shmem_write(struct drm_i915_gem_object *obj,
>  	if ((obj->ops->flags & I915_GEM_OBJECT_HAS_STRUCT_PAGE) == 0)
>  		return -EINVAL;
>  
> +	i915_gem_object_flush_gtt_write_domain(obj);
> +
>  	if (obj->base.write_domain != I915_GEM_DOMAIN_CPU) {
>  		ret = i915_gem_object_wait_rendering(obj, false);
>  		if (ret)
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation