[patch 020/100] drm: Use pgprot_writecombine in GEM GTT mapping to get the right bits for !PAT.

Chris Wright
2009-04-23T07:32:25Z

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-stable review patch. If anyone has any objections, please let us know.
---------------------

From: Jesse Barnes <jbarnes@virtuousgeek.org>

upstream commit: 1055f9ddad093f54dfd708a0f976582034d4ce1a

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>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---
drivers/gpu/drm/drm_gem.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)

--- 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, stru
struct drm_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, stru
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.