linux-kernel - [PATCH 3.16.y-ckt 046/118] drm/radeon: Don't flush the GART TLB if rdev->gart.ptr == NULL

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Date:	Wed, 12 Aug 2015 09:55:48 +0100
From:	Luis Henriques <luis.henriques@...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>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 046/118] drm/radeon: Don't flush the GART TLB if rdev->gart.ptr == NULL

3.16.7-ckt16 -stable review patch.  If anyone has any objections, please let me know.

------------------

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

commit 233709d2cd6bbaaeda0aeb8d11f6ca7f98563b39 upstream.

This can be the case when the GPU is powered off, e.g. via vgaswitcheroo
or runpm. When the GPU is powered up again, radeon_gart_table_vram_pin
flushes the TLB after setting rdev->gart.ptr to non-NULL.

Fixes panic on powering off R7xx GPUs.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=61529
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: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/gpu/drm/radeon/radeon_gart.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_gart.c b/drivers/gpu/drm/radeon/radeon_gart.c
index 2e723651069b..4259a1fa323f 100644
--- a/drivers/gpu/drm/radeon/radeon_gart.c
+++ b/drivers/gpu/drm/radeon/radeon_gart.c
@@ -249,8 +249,10 @@ void radeon_gart_unbind(struct radeon_device *rdev, unsigned offset,
 			}
 		}
 	}
-	mb();
-	radeon_gart_tlb_flush(rdev);
+	if (rdev->gart.ptr) {
+		mb();
+		radeon_gart_tlb_flush(rdev);
+	}
 }
 
 /**
@@ -292,8 +294,10 @@ int radeon_gart_bind(struct radeon_device *rdev, unsigned offset,
 			}
 		}
 	}
-	mb();
-	radeon_gart_tlb_flush(rdev);
+	if (rdev->gart.ptr) {
+		mb();
+		radeon_gart_tlb_flush(rdev);
+	}
 	return 0;
 }
 
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