linux-kernel - [PATCH] igbvf: Remove useless DMA-32 fallback configuration

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Message-Id: <dc75b24883381a060eaad21cb0deffb5a027b05f.1641753812.git.christophe.jaillet@wanadoo.fr>
Date:   Sun,  9 Jan 2022 19:43:40 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org
Subject: [PATCH] igbvf: 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@...adoo.fr>
---
This patch was not part of the 1st serie I've sent. So there is no
Reviewed-by tag.
---
 drivers/net/ethernet/intel/igbvf/netdev.c | 22 ++++++----------------
 1 file changed, 6 insertions(+), 16 deletions(-)

diff --git a/drivers/net/ethernet/intel/igbvf/netdev.c b/drivers/net/ethernet/intel/igbvf/netdev.c
index b78407289741..43ced78c3a2e 100644
--- a/drivers/net/ethernet/intel/igbvf/netdev.c
+++ b/drivers/net/ethernet/intel/igbvf/netdev.c
@@ -2684,25 +2684,18 @@ static int igbvf_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	struct igbvf_adapter *adapter;
 	struct e1000_hw *hw;
 	const struct igbvf_info *ei = igbvf_info_tbl[ent->driver_data];
-
 	static int cards_found;
-	int err, pci_using_dac;
+	int err;
 
 	err = pci_enable_device_mem(pdev);
 	if (err)
 		return err;
 
-	pci_using_dac = 0;
 	err = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
-	if (!err) {
-		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;
-		}
+	if (err) {
+		dev_err(&pdev->dev,
+			"No usable DMA configuration, aborting\n");
+		goto err_dma;
 	}
 
 	err = pci_request_regions(pdev, igbvf_driver_name);
@@ -2783,10 +2776,7 @@ static int igbvf_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	netdev->hw_features |= NETIF_F_GSO_PARTIAL |
 			       IGBVF_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_HW_CSUM;
-- 
2.32.0