drm/radeon: work around a hw bug in MGCG on CIK

Always need to set bit 0 of RLC_CGTT_MGCG_OVERRIDE
to avoid unreliable doorbell updates in some cases.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

diff --git a/drivers/gpu/drm/radeon/cik.c b/drivers/gpu/drm/radeon/cik.c
index bce73b6..cef4cb7 100644 (file)
--- a/drivers/gpu/drm/radeon/cik.c
+++ b/drivers/gpu/drm/radeon/cik.c
@@ -6344,6 +6344,7 @@ static void cik_enable_mgcg(struct radeon_device *rdev, bool enable)
                }
 
                orig = data = RREG32(RLC_CGTT_MGCG_OVERRIDE);
+               data |= 0x00000001;
                data &= 0xfffffffd;
                if (orig != data)
                        WREG32(RLC_CGTT_MGCG_OVERRIDE, data);
@@ -6377,7 +6378,7 @@ static void cik_enable_mgcg(struct radeon_device *rdev, bool enable)
                }
        } else {
                orig = data = RREG32(RLC_CGTT_MGCG_OVERRIDE);
-               data |= 0x00000002;
+               data |= 0x00000003;
                if (orig != data)
                        WREG32(RLC_CGTT_MGCG_OVERRIDE, data);