[PATCH] drm/ttm: do not try to preserve caching state

[j.glisse at gmail.com]

From: Jerome Glisse <jglisse at redhat.com>

It make no sense to preserve caching state especialy when
moving from vram to system. It burden the page allocator to
match the vram caching (often WC) which just burn CPU cycle
for no good reasons.

Signed-off-by: Jerome Glisse <jglisse at redhat.com>
---
 drivers/gpu/drm/ttm/ttm_bo.c | 15 +++------------
 1 file changed, 3 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index bf6e4b5..39dcc58 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -896,19 +896,12 @@ static int ttm_bo_mem_force_space(struct ttm_buffer_object *bo,
 }
 
 static uint32_t ttm_bo_select_caching(struct ttm_mem_type_manager *man,
-				      uint32_t cur_placement,
 				      uint32_t proposed_placement)
 {
 	uint32_t caching = proposed_placement & TTM_PL_MASK_CACHING;
 	uint32_t result = proposed_placement & ~TTM_PL_MASK_CACHING;
 
-	/**
-	 * Keep current caching if possible.
-	 */
-
-	if ((cur_placement & caching) != 0)
-		result |= (cur_placement & caching);
-	else if ((man->default_caching & caching) != 0)
+	if ((man->default_caching & caching) != 0)
 		result |= man->default_caching;
 	else if ((TTM_PL_FLAG_CACHED & caching) != 0)
 		result |= TTM_PL_FLAG_CACHED;
@@ -978,8 +971,7 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo,
 		if (!type_ok)
 			continue;
 
-		cur_flags = ttm_bo_select_caching(man, bo->mem.placement,
-						  cur_flags);
+		cur_flags = ttm_bo_select_caching(man, cur_flags);
 		/*
 		 * Use the access and other non-mapping-related flag bits from
 		 * the memory placement flags to the current flags
@@ -1023,8 +1015,7 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo,
 						&cur_flags))
 			continue;
 
-		cur_flags = ttm_bo_select_caching(man, bo->mem.placement,
-						  cur_flags);
+		cur_flags = ttm_bo_select_caching(man, cur_flags);
 		/*
 		 * Use the access and other non-mapping-related flag bits from
 		 * the memory placement flags to the current flags
-- 
1.7.11.7