[PATCH 3/4] drm/vmwgfx: fix the check when to use dma_alloc_coherent

[Thomas Hellstrom]

From: Christoph Hellwig <hch at lst.de>

Since Linux 4.21 we merged the swiotlb ops into the DMA direct ops,
so they would always have a the sync_single methods.  But late in
the cicle we also removed the direct ops entirely, so we'd see NULL
DMA ops.  Switch vmw_dma_select_mode to only detect swiotlb presence
using swiotlb_nr_tbl() instead.

Fixes: 55897af630 ("dma-direct: merge swiotlb_dma_ops into the dma_direct code")
Fixes: 356da6d0cd ("dma-mapping: bypass indirect calls for dma-direct")
Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
index b7777b5b4a81..1456101e67a9 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
@@ -565,7 +565,6 @@ static int vmw_dma_select_mode(struct vmw_private *dev_priv)
 		[vmw_dma_alloc_coherent] = "Using coherent TTM pages.",
 		[vmw_dma_map_populate] = "Keeping DMA mappings.",
 		[vmw_dma_map_bind] = "Giving up DMA mappings early."};
-	const struct dma_map_ops *dma_ops = get_dma_ops(dev_priv->dev->dev);
 
 	if (intel_iommu_enabled) {
 		dev_priv->map_mode = vmw_dma_map_populate;
@@ -578,14 +577,12 @@ static int vmw_dma_select_mode(struct vmw_private *dev_priv)
 		return 0;
 	}
 
-	dev_priv->map_mode = vmw_dma_map_populate;
-
-	if (dma_ops && dma_ops->sync_single_for_cpu)
-		dev_priv->map_mode = vmw_dma_alloc_coherent;
 #ifdef CONFIG_SWIOTLB
-	if (swiotlb_nr_tbl() == 0)
-		dev_priv->map_mode = vmw_dma_map_populate;
+	if (swiotlb_nr_tbl())
+		dev_priv->map_mode = vmw_dma_alloc_coherent;
+	else
 #endif
+		dev_priv->map_mode = vmw_dma_map_populate;
 
 out_fixup:
 	if (dev_priv->map_mode == vmw_dma_map_populate &&
-- 
2.19.0.rc1