[PATCH 2.6.38-10-generic] device driver: fix oops in radeon driverdue to incorrect value from hardware

From: Mayank Rungta
Date: Tue Aug 09 2011 - 14:23:04 EST

Added a check for the radeon ring buffer write index in r600.c which reads 0xffffffff on resume. This results in an Oops during radeon_ring_write. Masking the value averts this.

This problem is not seen to be fixed in 3.0 r600.c as well.

Detailed analysis of the problem can be found at -



BUG: unable to handle kernel paging request at fa501ffc - Oops at r600_cp_start+0x48/0x380 in r600_cp_resume+0x345/0x580 [radeon]


--- linux-2.6.38/drivers/gpu/drm/radeon/r600.c.orig 2011-08-05 15:39:40.824612700 +0530
+++ linux-2.6.38/drivers/gpu/drm/radeon/r600.c 2011-08-08 05:29:21.744417857 +0530
@@ -2218,6 +2218,8 @@ int r600_cp_resume(struct radeon_device

rdev->cp.rptr = RREG32(CP_RB_RPTR);
rdev->cp.wptr = RREG32(CP_RB_WPTR);
+ /* protect against crazy HW on resume */
+ rdev->cp.wptr &= rdev->cp.ptr_mask;

rdev->cp.ready = true;

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Signed-off-by: A R Karthick <a.r.karthick@xxxxxxxxx>

Reported-by: Mayank Rungta <mr.mynk@xxxxxxxxx>

Tested-by: Mayank Rungta <mr.mynk@xxxxxxxxx>
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