drm: Use pgprot_writecombine in GEM GTT mapping to get the right bits for !PAT.

Otherwise, the PAGE_CACHE_WC would end up getting us a UC-only mapping, and
the write performance of GTT maps dropped 10x.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
[anholt: cleaned up unused var]
Signed-off-by: Eric Anholt <eric@anholt.net>

1 files changed, 1 insertions, 6 deletions

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index c1173d8c4588..4984aa89cf3d 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -505,7 +505,6 @@ int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
         struct drm_local_map *map = NULL;
         struct drm_gem_object *obj;
         struct drm_hash_item *hash;
-        unsigned long prot;
         int ret = 0;
 
         mutex_lock(&dev->struct_mutex);
@@ -538,11 +537,7 @@ int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
         vma->vm_ops = obj->dev->driver->gem_vm_ops;
         vma->vm_private_data = map->handle;
         /* FIXME: use pgprot_writecombine when available */
-        prot = pgprot_val(vma->vm_page_prot);
-#ifdef CONFIG_X86
-        prot |= _PAGE_CACHE_WC;
-#endif
-        vma->vm_page_prot = __pgprot(prot);
+        vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
 
         /* Take a ref for this mapping of the object, so that the fault
          * handler can dereference the mmap offset's pointer to the object.