[1/4] drm/i915: Drop wmb() inside pread_gtt
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Message ID 20190718145407.21352-1-chris@chris-wilson.co.uk
State New
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Series
  • [1/4] drm/i915: Drop wmb() inside pread_gtt
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Commit Message

Chris Wilson July 18, 2019, 2:54 p.m. UTC
Inside pread, we only ever read from the GTT so the serialising wmb()
instructions around the GGTT PTE updates are pointless.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem.c | 3 ---
 1 file changed, 3 deletions(-)

Comments

Ville Syrjala July 18, 2019, 6:23 p.m. UTC | #1
On Thu, Jul 18, 2019 at 03:54:04PM +0100, Chris Wilson wrote:
> Inside pread, we only ever read from the GTT so the serialising wmb()
> instructions around the GGTT PTE updates are pointless.

Hard to argue with that.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_gem.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index a207b90924e4..fed0bc421a55 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -395,11 +395,9 @@ i915_gem_gtt_pread(struct drm_i915_gem_object *obj,
>  		unsigned page_length = PAGE_SIZE - page_offset;
>  		page_length = remain < page_length ? remain : page_length;
>  		if (node.allocated) {
> -			wmb();
>  			ggtt->vm.insert_page(&ggtt->vm,
>  					     i915_gem_object_get_dma_address(obj, offset >> PAGE_SHIFT),
>  					     node.start, I915_CACHE_NONE, 0);
> -			wmb();
>  		} else {
>  			page_base += offset & PAGE_MASK;
>  		}
> @@ -419,7 +417,6 @@ i915_gem_gtt_pread(struct drm_i915_gem_object *obj,
>  out_unpin:
>  	mutex_lock(&i915->drm.struct_mutex);
>  	if (node.allocated) {
> -		wmb();
>  		ggtt->vm.clear_range(&ggtt->vm, node.start, node.size);
>  		remove_mappable_node(&node);
>  	} else {
> -- 
> 2.22.0
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

Patch
diff mbox series

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index a207b90924e4..fed0bc421a55 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -395,11 +395,9 @@  i915_gem_gtt_pread(struct drm_i915_gem_object *obj,
 		unsigned page_length = PAGE_SIZE - page_offset;
 		page_length = remain < page_length ? remain : page_length;
 		if (node.allocated) {
-			wmb();
 			ggtt->vm.insert_page(&ggtt->vm,
 					     i915_gem_object_get_dma_address(obj, offset >> PAGE_SHIFT),
 					     node.start, I915_CACHE_NONE, 0);
-			wmb();
 		} else {
 			page_base += offset & PAGE_MASK;
 		}
@@ -419,7 +417,6 @@  i915_gem_gtt_pread(struct drm_i915_gem_object *obj,
 out_unpin:
 	mutex_lock(&i915->drm.struct_mutex);
 	if (node.allocated) {
-		wmb();
 		ggtt->vm.clear_range(&ggtt->vm, node.start, node.size);
 		remove_mappable_node(&node);
 	} else {