net: qcom/emac: specify the correct DMA mask

The 64/32-bit DMA mask hackery in the EMAC driver is not actually necessary,
and is technically not accurate.  The EMAC hardware is limted to a 45-bit
DMA address.  Although no EMAC-enabled system can have that much DDR,
an IOMMU could possible provide a larger address.  Rather than play games
with the DMA mappings, the driver should provide a correct value and
trust the DMA/IOMMU layers to do the right thing.

Signed-off-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 13 deletions

diff --git a/drivers/net/ethernet/qualcomm/emac/emac.c b/drivers/net/ethernet/qualcomm/emac/emac.c
index f477ba29c569..ee6f2d27502c 100644
--- a/drivers/net/ethernet/qualcomm/emac/emac.c
+++ b/drivers/net/ethernet/qualcomm/emac/emac.c
@@ -615,20 +615,11 @@ static int emac_probe(struct platform_device *pdev)
         u32 reg;
         int ret;
 
-        /* The EMAC itself is capable of 64-bit DMA, so try that first. */
-        ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
+        /* The TPD buffer address is limited to 45 bits. */
+        ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(45));
         if (ret) {
-                /* Some platforms may restrict the EMAC's address bus to less
-                 * then the size of DDR. In this case, we need to try a
-                 * smaller mask.  We could try every possible smaller mask,
-                 * but that's overkill.  Instead, just fall to 32-bit, which
-                 * should always work.
-                 */
-                ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
-                if (ret) {
-                        dev_err(&pdev->dev, "could not set DMA mask\n");
-                        return ret;
-                }
+                dev_err(&pdev->dev, "could not set DMA mask\n");
+                return ret;
         }
 
         netdev = alloc_etherdev(sizeof(struct emac_adapter));