Re: [PATCH 1/4] drm/i915: Clearing buffer objects via CPU/GTT

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

On 09/15/2015 09:33 AM, ankitprasad.r.sharma@intel.com wrote:
> From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
>
> This patch adds support for clearing buffer objects via CPU/GTT. This
> is particularly useful for clearing out the non shmem backed objects.
> Currently intend to use this only for buffers allocated from stolen
> region.
>
> v2: Added kernel doc for i915_gem_clear_object(), corrected/removed
> variable assignments (Tvrtko)
>
> Testcase: igt/gem_stolen
>
> Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_drv.h |  1 +
>   drivers/gpu/drm/i915/i915_gem.c | 39 +++++++++++++++++++++++++++++++++++++++
>   2 files changed, 40 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index e0f3f05..8db905a 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2820,6 +2820,7 @@ int i915_gem_obj_prepare_shmem_read(struct drm_i915_gem_object *obj,
>   				    int *needs_clflush);
>
>   int __must_check i915_gem_object_get_pages(struct drm_i915_gem_object *obj);
> +int i915_gem_clear_object(struct drm_i915_gem_object *obj);
>
>   static inline int __sg_page_count(struct scatterlist *sg)
>   {
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 1ac57ec..94533bf 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -5139,3 +5139,42 @@ fail:
>   	drm_gem_object_unreference(&obj->base);
>   	return ERR_PTR(ret);
>   }
> +
> +/**
> + * i915_gem_clear_object() - Clear buffer object via CPU/GTT
> + * @obj: Buffer object to be cleared
> + *
> + * Return: 0 - success, non-zero - failure
> + */
> +int i915_gem_clear_object(struct drm_i915_gem_object *obj)
> +{
> +	int ret;
> +	char __iomem *base;
> +	size_t size = obj->base.size;
> +	struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
> +
> +	WARN_ON(!mutex_is_locked(&obj->base.dev->struct_mutex));
> +	ret = i915_gem_obj_ggtt_pin(obj, 0, PIN_MAPPABLE);
> +	if (ret)
> +		return ret;
> +
> +	ret = i915_gem_object_put_fence(obj);
> +	if (ret)
> +		goto unpin;
> +
> +	/* Get the CPU virtual address of the buffer */
> +	base = ioremap_wc(dev_priv->gtt.mappable_base +
> +				i915_gem_obj_ggtt_offset(obj), size);
> +	if (base == NULL) {
> +		DRM_ERROR("Mapping of gem object to CPU failed!\n");
> +		ret = -ENOSPC;
> +		goto unpin;
> +	}
> +
> +	memset_io(base, 0, size);
> +
> +	iounmap(base);
> +unpin:
> +	i915_gem_object_ggtt_unpin(obj);
> +	return ret;
> +}
>

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

Regards,

Tvrtko
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