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>

diff --git a/drivers/net/ethernet/qualcomm/emac/emac.c b/drivers/net/ethernet/qualcomm/emac/emac.c
index f477ba2..ee6f2d2 100644 (file)
--- 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));