netdev - [net-next 15/15] ixgbe: don't set RXDCTL.RLPML for 82599

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Message-Id: <20180126182626.23462-16-jeffrey.t.kirsher@intel.com>
Date:   Fri, 26 Jan 2018 10:26:26 -0800
From:   Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:     davem@...emloft.net
Cc:     Emil Tantilov <emil.s.tantilov@...el.com>, netdev@...r.kernel.org,
        nhorman@...hat.com, sassmann@...hat.com, jogreene@...hat.com,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: [net-next 15/15] ixgbe: don't set RXDCTL.RLPML for 82599

From: Emil Tantilov <emil.s.tantilov@...el.com>

commit 2de6aa3a666e ("ixgbe: Add support for padding packet")

Uses RXDCTL.RLPML to limit the maximum frame size on Rx when using
build_skb. Unfortunately that register does not work on 82599.

Added an explicit check to avoid setting this register on 82599 MAC.

Extended the comment related to the setting of RXDCTL.RLPML to better
explain its purpose.

Signed-off-by: Emil Tantilov <emil.s.tantilov@...el.com>
Tested-by: Andrew Bowers <andrewx.bowers@...el.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
---
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 643c7288ea0f..0da5aa2c8aba 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -4133,11 +4133,15 @@ void ixgbe_configure_rx_ring(struct ixgbe_adapter *adapter,
 		rxdctl &= ~0x3FFFFF;
 		rxdctl |=  0x080420;
 #if (PAGE_SIZE < 8192)
-	} else {
+	/* RXDCTL.RLPML does not work on 82599 */
+	} else if (hw->mac.type != ixgbe_mac_82599EB) {
 		rxdctl &= ~(IXGBE_RXDCTL_RLPMLMASK |
 			    IXGBE_RXDCTL_RLPML_EN);
 
-		/* Limit the maximum frame size so we don't overrun the skb */
+		/* Limit the maximum frame size so we don't overrun the skb.
+		 * This can happen in SRIOV mode when the MTU of the VF is
+		 * higher than the MTU of the PF.
+		 */
 		if (ring_uses_build_skb(ring) &&
 		    !test_bit(__IXGBE_RX_3K_BUFFER, &ring->state))
 			rxdctl |= IXGBE_MAX_2K_FRAME_BUILD_SKB |
-- 
2.14.3