drm/radeon: fixup bad vram size on SI

Some boards seem to have garbage in the upper
16 bits of the vram size register.  Check for
this and clamp the size properly.  Fixes
boards reporting bogus amounts of vram.

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

1 files changed, 9 insertions, 2 deletions

diff --git a/drivers/gpu/drm/radeon/si.c b/drivers/gpu/drm/radeon/si.c
index 6a64ccaa0695..a36736dab5e0 100644
--- a/drivers/gpu/drm/radeon/si.c
+++ b/drivers/gpu/drm/radeon/si.c
@@ -3882,8 +3882,15 @@ static int si_mc_init(struct radeon_device *rdev)
         rdev->mc.aper_base = pci_resource_start(rdev->pdev, 0);
         rdev->mc.aper_size = pci_resource_len(rdev->pdev, 0);
         /* size in MB on si */
-        rdev->mc.mc_vram_size = RREG32(CONFIG_MEMSIZE) * 1024ULL * 1024ULL;
-        rdev->mc.real_vram_size = RREG32(CONFIG_MEMSIZE) * 1024ULL * 1024ULL;
+        tmp = RREG32(CONFIG_MEMSIZE);
+        /* some boards may have garbage in the upper 16 bits */
+        if (tmp & 0xffff0000) {
+                DRM_INFO("Probable bad vram size: 0x%08x\n", tmp);
+                if (tmp & 0xffff)
+                        tmp &= 0xffff;
+        }
+        rdev->mc.mc_vram_size = tmp * 1024ULL * 1024ULL;
+        rdev->mc.real_vram_size = rdev->mc.mc_vram_size;
         rdev->mc.visible_vram_size = rdev->mc.aper_size;
         si_vram_gtt_location(rdev, &rdev->mc);
         radeon_update_bandwidth_info(rdev);