This is a note to let you know that I've just added the patch titled
drm/radeon: Don't try to enable write-combining without PAT
to the 3.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-radeon-don-t-try-to-enable-write-combining-without-pat.patch
and it can be found in the queue-3.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a53fa43873b88bad15a2eb1f01dc5efa689625ce Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michel=20D=C3=A4nzer?= <michel.daenzer@xxxxxxx>
Date: Wed, 4 Feb 2015 10:19:51 +0900
Subject: drm/radeon: Don't try to enable write-combining without PAT
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From: =?UTF-8?q?Michel=20D=C3=A4nzer?= <michel.daenzer@xxxxxxx>
commit a53fa43873b88bad15a2eb1f01dc5efa689625ce upstream.
Doing so can cause things to become slow.
Print a warning at compile time and an informative message at runtime in
that case.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=88758
Reviewed-by: Christian König <christian.koenig@xxxxxxx>
Signed-off-by: Michel Dänzer <michel.daenzer@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/radeon/radeon_object.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
--- a/drivers/gpu/drm/radeon/radeon_object.c
+++ b/drivers/gpu/drm/radeon/radeon_object.c
@@ -238,6 +238,18 @@ int radeon_bo_create(struct radeon_devic
* See https://bugs.freedesktop.org/show_bug.cgi?id=84627
*/
bo->flags &= ~RADEON_GEM_GTT_WC;
+#elif defined(CONFIG_X86) && !defined(CONFIG_X86_PAT)
+ /* Don't try to enable write-combining when it can't work, or things
+ * may be slow
+ * See https://bugs.freedesktop.org/show_bug.cgi?id=88758
+ */
+
+#warning Please enable CONFIG_MTRR and CONFIG_X86_PAT for better performance \
+ thanks to write-combining
+
+ DRM_INFO_ONCE("Please enable CONFIG_MTRR and CONFIG_X86_PAT for "
+ "better performance thanks to write-combining\n");
+ bo->flags &= ~RADEON_GEM_GTT_WC;
#endif
radeon_ttm_placement_from_domain(bo, domain);
Patches currently in stable-queue which might be from michel.daenzer@xxxxxxx are
queue-3.19/drm-radeon-don-t-try-to-enable-write-combining-without-pat.patch
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