As stated in [1], dma_set_mask() with a 64-bit mask never fails if
dev->dma_mask is non-NULL.
So, if it fails, the 32 bits case will also fail for the same reason.

So, if dma_set_mask_and_coherent() succeeds, 'pci_using_dac' is known to be
1.

Simplify code and remove some dead code accordingly.

[1]: https://lkml.org/lkml/2021/6/7/398

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>
---
 .../net/ethernet/intel/ixgbevf/ixgbevf_main.c | 20 ++++++-------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
index 0015fcf1df2b..7c33be9074e9 100644
--- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
+++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
@@ -4511,22 +4511,17 @@ static int ixgbevf_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	struct ixgbevf_adapter *adapter = NULL;
 	struct ixgbe_hw *hw = NULL;
 	const struct ixgbevf_info *ii = ixgbevf_info_tbl[ent->driver_data];
-	int err, pci_using_dac;
 	bool disable_dev = false;
+	int err;
 
 	err = pci_enable_device(pdev);
 	if (err)
 		return err;
 
-	if (!dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64))) {
-		pci_using_dac = 1;
-	} else {
-		err = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
-		if (err) {
-			dev_err(&pdev->dev, "No usable DMA configuration, aborting\n");
-			goto err_dma;
-		}
-		pci_using_dac = 0;
+	err = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
+	if (err) {
+		dev_err(&pdev->dev, "No usable DMA configuration, aborting\n");
+		goto err_dma;
 	}
 
 	err = pci_request_regions(pdev, ixgbevf_driver_name);
@@ -4606,10 +4601,7 @@ static int ixgbevf_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	netdev->hw_features |= NETIF_F_GSO_PARTIAL |
 			       IXGBEVF_GSO_PARTIAL_FEATURES;
 
-	netdev->features = netdev->hw_features;
-
-	if (pci_using_dac)
-		netdev->features |= NETIF_F_HIGHDMA;
+	netdev->features = netdev->hw_features | NETIF_F_HIGHDMA;
 
 	netdev->vlan_features |= netdev->features | NETIF_F_TSO_MANGLEID;
 	netdev->mpls_features |= NETIF_F_SG |
-- 
2.32.0

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@osuosl.org> On Behalf Of
> Christophe JAILLET
> Sent: Sunday, January 9, 2022 10:52 PM
> To: Brandeburg, Jesse <jesse.brandeburg@intel.com>; Nguyen, Anthony L
> <anthony.l.nguyen@intel.com>; David S. Miller <davem@davemloft.net>;
> Jakub Kicinski <kuba@kernel.org>
> Cc: netdev@vger.kernel.org; kernel-janitors@vger.kernel.org; linux-
> kernel@vger.kernel.org; Christophe JAILLET
> <christophe.jaillet@wanadoo.fr>; intel-wired-lan@lists.osuosl.org; Christoph
> Hellwig <hch@lst.de>
> Subject: [Intel-wired-lan] [PATCH] ixgbevf: Remove useless DMA-32 fallback
> configuration
> 
> As stated in [1], dma_set_mask() with a 64-bit mask never fails if
> dev->dma_mask is non-NULL.
> So, if it fails, the 32 bits case will also fail for the same reason.
> 
> So, if dma_set_mask_and_coherent() succeeds, 'pci_using_dac' is known to
> be 1.
> 
> Simplify code and remove some dead code accordingly.
> 
> [1]: https://lkml.org/lkml/2021/6/7/398
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>
> ---
>  .../net/ethernet/intel/ixgbevf/ixgbevf_main.c | 20 ++++++-------------
>  1 file changed, 6 insertions(+), 14 deletions(-)
> 

Tested-by: Gurucharan G <gurucharanx.g@intel.com> (A Contingent worker at Intel)