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net: qcom/emac: specify the correct DMA mask

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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>
This commit is contained in:
Timur Tabi 2017-10-11 14:52:23 -05:00 committed by David S. Miller
parent c7c64bca62
commit d7e6b34756
1 changed files with 4 additions and 13 deletions
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17
drivers/net/ethernet/qualcomm/emac/emac.c
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@ -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));