sfc: simplify DMA mask setting

Christoph says[1] that dma_set_mask_and_coherent() is smart enough to
 truncate the mask itself if it's too long.  So we can get rid of our
 "lop off one bit and retry" loop in efx_init_io().

[1]: https://www.spinics.net/lists/netdev/msg677266.html

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/sfc/efx_common.c b/drivers/net/ethernet/sfc/efx_common.c
index 9eda54e..80a23de 100644 (file)
--- a/drivers/net/ethernet/sfc/efx_common.c
+++ b/drivers/net/ethernet/sfc/efx_common.c
@@ -1086,17 +1086,7 @@ int efx_init_io(struct efx_nic *efx, int bar, dma_addr_t dma_mask,
 
        pci_set_master(pci_dev);
 
-       /* Set the PCI DMA mask.  Try all possibilities from our
-        * genuine mask down to 32 bits, because some architectures
-        * (e.g. x86_64 with iommu_sac_force set) will allow 40 bit
-        * masks event though they reject 46 bit masks.
-        */
-       while (dma_mask > 0x7fffffffUL) {
-               rc = dma_set_mask_and_coherent(&pci_dev->dev, dma_mask);
-               if (rc == 0)
-                       break;
-               dma_mask >>= 1;
-       }
+       rc = dma_set_mask_and_coherent(&pci_dev->dev, dma_mask);
        if (rc) {
                netif_err(efx, probe, efx->net_dev,
                          "could not find a suitable DMA mask\n");