drm/radeon/kms: fix r300 vram width calculations

This was incorrect according to the docs and the UMS driver does
it like this.

Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/drivers/gpu/drm/radeon/r300.c b/drivers/gpu/drm/radeon/r300.c
index e699e6d053dd..43b55a030b4d 100644
--- a/drivers/gpu/drm/radeon/r300.c
+++ b/drivers/gpu/drm/radeon/r300.c
@@ -506,11 +506,14 @@ void r300_vram_info(struct radeon_device *rdev)
 
         /* DDR for all card after R300 & IGP */
         rdev->mc.vram_is_ddr = true;
+
         tmp = RREG32(RADEON_MEM_CNTL);
-        if (tmp & R300_MEM_NUM_CHANNELS_MASK) {
-                rdev->mc.vram_width = 128;
-        } else {
-                rdev->mc.vram_width = 64;
+        tmp &= R300_MEM_NUM_CHANNELS_MASK;
+        switch (tmp) {
+        case 0: rdev->mc.vram_width = 64; break;
+        case 1: rdev->mc.vram_width = 128; break;
+        case 2: rdev->mc.vram_width = 256; break;
+        default:  rdev->mc.vram_width = 128; break;
         }
 
         r100_vram_init_sizes(rdev);