drm/radeon/kms: fix tiling reg on fusion

The location of MC_ARB_RAMCFG changed on fusion.
I've diffed all the other regs in evergreend.h and this
is the only other reg that changed.
Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/evergreen.c

@@ -1780,7 +1780,10 @@ static void evergreen_gpu_init(struct radeon_device *rdev)
 
 
 	mc_shared_chmap = RREG32(MC_SHARED_CHMAP);
-	mc_arb_ramcfg = RREG32(MC_ARB_RAMCFG);
+	if (rdev->flags & RADEON_IS_IGP)
+		mc_arb_ramcfg = RREG32(FUS_MC_ARB_RAMCFG);
+	else
+		mc_arb_ramcfg = RREG32(MC_ARB_RAMCFG);
 
 	switch (rdev->config.evergreen.max_tile_pipes) {
 	case 1:

drivers/gpu/drm/radeon/evergreend.h

@@ -200,6 +200,7 @@
 #define		BURSTLENGTH_SHIFT				9
 #define		BURSTLENGTH_MASK				0x00000200
 #define		CHANSIZE_OVERRIDE				(1 << 11)
+#define	FUS_MC_ARB_RAMCFG				0x2768
 #define	MC_VM_AGP_TOP					0x2028
 #define	MC_VM_AGP_BOT					0x202C
 #define	MC_VM_AGP_BASE					0x2030