1 files changed, 8 insertions, 1 deletions

diff --git a/drivers/char/drm/via_dma.c b/drivers/char/drm/via_dma.c
index a691ae74129d..c0539c6299cf 100644
--- a/drivers/char/drm/via_dma.c
+++ b/drivers/char/drm/via_dma.c
@@ -190,6 +190,11 @@ static int via_initialize(drm_device_t * dev,
                 return DRM_ERR(EFAULT);
         }
 
+        if (dev_priv->chipset == VIA_DX9_0) {
+                DRM_ERROR("AGP DMA is not supported on this chip\n");
+                return DRM_ERR(EINVAL);
+        }
+
         dev_priv->ring.map.offset = dev->agp->base + init->offset;
         dev_priv->ring.map.size = init->size;
         dev_priv->ring.map.type = 0;
@@ -480,6 +485,7 @@ static int via_hook_segment(drm_via_private_t * dev_priv,
                         VIA_WRITE(VIA_REG_TRANSET, (HC_ParaType_PreCR << 16));
                         VIA_WRITE(VIA_REG_TRANSPACE, pause_addr_hi);
                         VIA_WRITE(VIA_REG_TRANSPACE, pause_addr_lo);
+                        VIA_READ(VIA_REG_TRANSPACE);
                 }
         }
         return paused;
@@ -557,8 +563,9 @@ static void via_cmdbuf_start(drm_via_private_t * dev_priv)
 
         VIA_WRITE(VIA_REG_TRANSPACE, pause_addr_hi);
         VIA_WRITE(VIA_REG_TRANSPACE, pause_addr_lo);
-
+        DRM_WRITEMEMORYBARRIER();
         VIA_WRITE(VIA_REG_TRANSPACE, command | HC_HAGPCMNT_MASK);
+        VIA_READ(VIA_REG_TRANSPACE);
 }
 
 static void via_pad_cache(drm_via_private_t * dev_priv, int qwords)