[V3,31/37] drm/ttm: Replace kmap_atomic() usage

Commit Message

Thomas Gleixner Nov. 3, 2020, 9:27 a.m. UTC

There is no reason to disable pagefaults and preemption as a side effect of
kmap_atomic_prot().

Use kmap_local_page_prot() instead and document the reasoning for the
mapping usage with the given pgprot.

Remove the NULL pointer check for the map. These functions return a valid
address for valid pages and the return was bogus anyway as it would have
left preemption and pagefaults disabled.

Signed-off-by: Thomas Gleixner <[e-mail]>
Cc: Christian Koenig <[e-mail]>
Cc: Huang Rui <[e-mail]>
Cc: David Airlie <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: [e-mail]
---
V3: New patch
---
 drivers/gpu/drm/ttm/ttm_bo_util.c |   20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

Patch

--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -181,13 +181,15 @@  static int ttm_copy_io_ttm_page(struct t
 		return -ENOMEM;
 
 	src = (void *)((unsigned long)src + (page << PAGE_SHIFT));
-	dst = kmap_atomic_prot(d, prot);
-	if (!dst)
-		return -ENOMEM;
+	/*
+	 * Ensure that a highmem page is mapped with the correct
+	 * pgprot. For non highmem the mapping is already there.
+	 */
+	dst = kmap_local_page_prot(d, prot);
 
 	memcpy_fromio(dst, src, PAGE_SIZE);
 
-	kunmap_atomic(dst);
+	kunmap_local(dst);
 
 	return 0;
 }
@@ -203,13 +205,15 @@  static int ttm_copy_ttm_io_page(struct t
 		return -ENOMEM;
 
 	dst = (void *)((unsigned long)dst + (page << PAGE_SHIFT));
-	src = kmap_atomic_prot(s, prot);
-	if (!src)
-		return -ENOMEM;
+	/*
+	 * Ensure that a highmem page is mapped with the correct
+	 * pgprot. For non highmem the mapping is already there.
+	 */
+	src = kmap_local_page_prot(s, prot);
 
 	memcpy_toio(dst, src, PAGE_SIZE);
 
-	kunmap_atomic(src);
+	kunmap_local(src);
 
 	return 0;
 }