linux-kernel - [PATCH 4.2.y-ckt 018/305] drm/radeon: Disable uncacheable CPU mappings of GTT with RV6xx

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Message-Id: <1452902519-2754-19-git-send-email-kamal@canonical.com>
Date:	Fri, 15 Jan 2016 15:57:12 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Michel Dänzer <michel.daenzer@....com>,
	Alex Deucher <alexander.deucher@....com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 018/305] drm/radeon: Disable uncacheable CPU mappings of GTT with RV6xx

4.2.8-ckt2 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: =?UTF-8?q?Michel=20D=C3=A4nzer?= <michel.daenzer@....com>

commit 96ea47c0ec8c012509116bee8c57414281428fc4 upstream.

They reportedly cause random GPU hangs.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91268

Reviewed-by: Christian König <christian.koenig@....com>
Signed-off-by: Michel Dänzer <michel.daenzer@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/gpu/drm/radeon/radeon_object.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/radeon/radeon_object.c b/drivers/gpu/drm/radeon/radeon_object.c
index 6763627..6e88c1b0 100644
--- a/drivers/gpu/drm/radeon/radeon_object.c
+++ b/drivers/gpu/drm/radeon/radeon_object.c
@@ -221,6 +221,12 @@ int radeon_bo_create(struct radeon_device *rdev,
 	if (!(rdev->flags & RADEON_IS_PCIE))
 		bo->flags &= ~(RADEON_GEM_GTT_WC | RADEON_GEM_GTT_UC);
 
+	/* Write-combined CPU mappings of GTT cause GPU hangs with RV6xx
+	 * See https://bugs.freedesktop.org/show_bug.cgi?id=91268
+	 */
+	if (rdev->family >= CHIP_RV610 && rdev->family <= CHIP_RV635)
+		bo->flags &= ~(RADEON_GEM_GTT_WC | RADEON_GEM_GTT_UC);
+
 #ifdef CONFIG_X86_32
 	/* XXX: Write-combined CPU mappings of GTT seem broken on 32-bit
 	 * See https://bugs.freedesktop.org/show_bug.cgi?id=84627
-- 
1.9.1