drm/radeon: Fix sideport problems on certain RS690 boards

Some RS690 boards with 64MB of sideport memory show up as
having 128MB sideport + 256MB of UMA.  In this case,
just skip the sideport memory and use UMA.  This fixes
rendering corruption and should improve performance.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=35457

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

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/gpu/drm/radeon/rs690.c b/drivers/gpu/drm/radeon/rs690.c
index 1c560629575a..e7dab069cccf 100644
--- a/drivers/gpu/drm/radeon/rs690.c
+++ b/drivers/gpu/drm/radeon/rs690.c
@@ -162,6 +162,16 @@ static void rs690_mc_init(struct radeon_device *rdev)
         base = RREG32_MC(R_000100_MCCFG_FB_LOCATION);
         base = G_000100_MC_FB_START(base) << 16;
         rdev->mc.igp_sideport_enabled = radeon_atombios_sideport_present(rdev);
+        /* Some boards seem to be configured for 128MB of sideport memory,
+         * but really only have 64MB.  Just skip the sideport and use
+         * UMA memory.
+         */
+        if (rdev->mc.igp_sideport_enabled &&
+            (rdev->mc.real_vram_size == (384 * 1024 * 1024))) {
+                base += 128 * 1024 * 1024;
+                rdev->mc.real_vram_size -= 128 * 1024 * 1024;
+                rdev->mc.mc_vram_size = rdev->mc.real_vram_size;
+        }
 
         /* Use K8 direct mapping for fast fb access. */ 
         rdev->fastfb_working = false;