diff --git a/drivers/char/drm/radeon_cp.c b/drivers/char/drm/radeon_cp.c
index 9f2b4ef..95ae9e0 100644
--- a/drivers/char/drm/radeon_cp.c
+++ b/drivers/char/drm/radeon_cp.c
@@ -1312,6 +1312,8 @@
 static int radeon_do_init_cp(drm_device_t * dev, drm_radeon_init_t * init)
 {
 	drm_radeon_private_t *dev_priv = dev->dev_private;;
+	unsigned int mem_size;
+
 	DRM_DEBUG("\n");
 
 	dev_priv->is_pci = init->is_pci;
@@ -1521,8 +1523,11 @@
 					  + dev_priv->fb_location) >> 10));
 
 	dev_priv->gart_size = init->gart_size;
-	dev_priv->gart_vm_start = dev_priv->fb_location
-	    + RADEON_READ(RADEON_CONFIG_APER_SIZE) * 2;
+
+	mem_size = RADEON_READ(RADEON_CONFIG_MEMSIZE);
+	if (mem_size == 0)
+		mem_size = 0x800000;
+	dev_priv->gart_vm_start = dev_priv->fb_location + mem_size;
 
 #if __OS_HAS_AGP
 	if (!dev_priv->is_pci)
diff --git a/drivers/char/drm/radeon_drv.h b/drivers/char/drm/radeon_drv.h
index 7bda7e3..d92ccee 100644
--- a/drivers/char/drm/radeon_drv.h
+++ b/drivers/char/drm/radeon_drv.h
@@ -379,6 +379,7 @@
 #	define RADEON_PLL_WR_EN			(1 << 7)
 #define RADEON_CLOCK_CNTL_INDEX		0x0008
 #define RADEON_CONFIG_APER_SIZE		0x0108
+#define RADEON_CONFIG_MEMSIZE		0x00f8
 #define RADEON_CRTC_OFFSET		0x0224
 #define RADEON_CRTC_OFFSET_CNTL		0x0228
 #	define RADEON_CRTC_TILE_EN		(1 << 15)