[PATCH 07/40] drm/i915: Consolidate checks for memcpy-from-wc support

[Tvrtko Ursulin]

On 05/01/2017 14:54, Chris Wilson wrote:
> In order to silence sparse:
>
> ../drivers/gpu/drm/i915/i915_gpu_error.c:200:39: warning: Using plain integer as NULL pointer
>
> add a helper to check whether we have sse4.1 and that the desired
> alignment is valid for acceleration.
>
> Reported-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_cmd_parser.c     |  2 +-
>  drivers/gpu/drm/i915/i915_drv.h            | 16 ++++++++++++++++
>  drivers/gpu/drm/i915/i915_gpu_error.c      |  2 +-
>  drivers/gpu/drm/i915/i915_guc_submission.c |  2 +-
>  4 files changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c
> index 6c310a8a97a7..21b1cd917d81 100644
> --- a/drivers/gpu/drm/i915/i915_cmd_parser.c
> +++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
> @@ -1079,7 +1079,7 @@ static u32 *copy_batch(struct drm_i915_gem_object *dst_obj,
>
>  	src = ERR_PTR(-ENODEV);
>  	if (src_needs_clflush &&
> -	    i915_memcpy_from_wc((void *)(uintptr_t)batch_start_offset, NULL, 0)) {
> +	    i915_can_memcpy_from_wc(NULL, batch_start_offset, 0)) {
>  		src = i915_gem_object_pin_map(src_obj, I915_MAP_WC);
>  		if (!IS_ERR(src)) {
>  			i915_memcpy_from_wc(dst,
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 7b436621d038..618c81b2726c 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -4032,6 +4032,22 @@ __i915_request_irq_complete(struct drm_i915_gem_request *req)
>  void i915_memcpy_init_early(struct drm_i915_private *dev_priv);
>  bool i915_memcpy_from_wc(void *dst, const void *src, unsigned long len);
>
> +/* The movntdqa instructions used for memcpy-from-wc require 16-byte alignment,
> + * as well as SSE4.1 support. i915_memcpy_from_wc() will report if it cannot
> + * perform the operation. To check beforehand, pass in the parameters to
> + * to i915_can_memcpy_from_wc() - since we only care about the low 4 bits,
> + * you only need to pass in the minor offsets, page-aligned pointers are
> + * always valid.
> + *
> + * For just checking for SSE4.1, in the foreknowlege that the future use

Just a typo in foreknowledge.

> + * will be correctly aligned, just use i915_has_memcpy_from_wc().
> + */
> +#define i915_can_memcpy_from_wc(dst, src, len) \
> +	i915_memcpy_from_wc((void *)((uintptr_t)(dst) | (uintptr_t)(src) | (len)), NULL, 0)

Minor, but why do you need uintptr_t casts here? I never like to see 
these types in the kernel. Could you cast len to void * just as well?

> +
> +#define i915_has_memcpy_from_wc() \
> +	i915_memcpy_from_wc(NULL, NULL, 0)
> +
>  /* i915_mm.c */
>  int remap_io_mapping(struct vm_area_struct *vma,
>  		     unsigned long addr, unsigned long pfn, unsigned long size,
> diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
> index e34532d98004..396c6f0fd033 100644
> --- a/drivers/gpu/drm/i915/i915_gpu_error.c
> +++ b/drivers/gpu/drm/i915/i915_gpu_error.c
> @@ -197,7 +197,7 @@ static bool compress_init(struct compress *c)
>  	}
>
>  	c->tmp = NULL;
> -	if (i915_memcpy_from_wc(NULL, 0, 0))
> +	if (i915_has_memcpy_from_wc())
>  		c->tmp = (void *)__get_free_page(GFP_ATOMIC | __GFP_NOWARN);
>
>  	return true;
> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
> index 30e012b9e93c..710fbb9fc63f 100644
> --- a/drivers/gpu/drm/i915/i915_guc_submission.c
> +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
> @@ -1197,7 +1197,7 @@ static void guc_log_create(struct intel_guc *guc)
>  		 * it should be present on the chipsets supporting GuC based
>  		 * submisssions.
>  		 */
> -		if (WARN_ON(!i915_memcpy_from_wc(NULL, NULL, 0))) {
> +		if (WARN_ON(!i915_has_memcpy_from_wc())) {
>  			/* logging will not be enabled */
>  			i915.guc_log_level = -1;
>  			return;
>

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

Regards,

Tvrtko