drm/ttm: fix caching problem on non-PAT systems.

http://bugzilla.kernel.org/show_bug.cgi?id=15328

This fixes a serious regression on AGP/non-PAT systems, where
pages were ending up in the wrong state and slowing down the
whole system.

[airlied: taken this from the bug as the other option is to revert
the change which caused it].

Tested-by: John W. Linville (in bug).
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
index e2123af..3d47a2c 100644 (file)
--- a/drivers/gpu/drm/ttm/ttm_tt.c
+++ b/drivers/gpu/drm/ttm/ttm_tt.c
@@ -196,14 +196,15 @@ EXPORT_SYMBOL(ttm_tt_populate);
 
 #ifdef CONFIG_X86
 static inline int ttm_tt_set_page_caching(struct page *p,
-                                         enum ttm_caching_state c_state)
+                                         enum ttm_caching_state c_old,
+                                         enum ttm_caching_state c_new)
 {
        int ret = 0;
 
        if (PageHighMem(p))
                return 0;
 
-       if (get_page_memtype(p) != -1) {
+       if (c_old != tt_cached) {
                /* p isn't in the default caching state, set it to
                 * writeback first to free its current memtype. */
 
@@ -212,16 +213,17 @@ static inline int ttm_tt_set_page_caching(struct page *p,
                        return ret;
        }
 
-       if (c_state == tt_wc)
+       if (c_new == tt_wc)
                ret = set_memory_wc((unsigned long) page_address(p), 1);
-       else if (c_state == tt_uncached)
+       else if (c_new == tt_uncached)
                ret = set_pages_uc(p, 1);
 
        return ret;
 }
 #else /* CONFIG_X86 */
 static inline int ttm_tt_set_page_caching(struct page *p,
-                                         enum ttm_caching_state c_state)
+                                         enum ttm_caching_state c_old,
+                                         enum ttm_caching_state c_new)
 {
        return 0;
 }
@@ -254,7 +256,9 @@ static int ttm_tt_set_caching(struct ttm_tt *ttm,
        for (i = 0; i < ttm->num_pages; ++i) {
                cur_page = ttm->pages[i];
                if (likely(cur_page != NULL)) {
-                       ret = ttm_tt_set_page_caching(cur_page, c_state);
+                       ret = ttm_tt_set_page_caching(cur_page,
+                                                     ttm->caching_state,
+                                                     c_state);
                        if (unlikely(ret != 0))
                                goto out_err;
                }
@@ -268,7 +272,7 @@ out_err:
        for (j = 0; j < i; ++j) {
                cur_page = ttm->pages[j];
                if (likely(cur_page != NULL)) {
-                       (void)ttm_tt_set_page_caching(cur_page,
+                       (void)ttm_tt_set_page_caching(cur_page, c_state,
                                                      ttm->caching_state);
                }
        }