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From:   =?UTF-8?q?St=C3=A9phane=20Graber?= <stgraber@ubuntu.com>
To:     netdev@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org,
        Iyappan Subramanian <iyappan@os.amperecomputing.com>,
        Keyur Chudgar <keyur@os.amperecomputing.com>,
        Quan Nguyen <quan@os.amperecomputing.com>,
        "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Toan Le <toan@os.amperecomputing.com>,
        Stephane Graber <stgraber@ubuntu.com>, stable@vger.kernel.org
Subject: [PATCH] drivers: net: xgene: Fix regression in CRC stripping
Date:   Thu, 17 Mar 2022 10:42:25 -0400
Message-Id: <20220317144225.4005500-1-stgraber@ubuntu.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
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From: Stephane Graber <stgraber@ubuntu.com>

All packets on ingress (except for jumbo) are terminated with a 4-bytes
CRC checksum. It's the responsability of the driver to strip those 4
bytes. Unfortunately a change dating back to March 2017 re-shuffled some
code and made the CRC stripping code effectively dead.

This change re-orders that part a bit such that the datalen is
immediately altered if needed.

Fixes: 4902a92270fb ("drivers: net: xgene: Add workaround for errata 10GE_8/ENET_11")
Signed-off-by: Stephane Graber <stgraber@ubuntu.com>
Tested-by: Stephane Graber <stgraber@ubuntu.com>
Cc: stable@vger.kernel.org
---
 drivers/net/ethernet/apm/xgene/xgene_enet_main.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
index ff2d099aab21..3892790f04e0 100644
--- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
+++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
@@ -696,6 +696,12 @@ static int xgene_enet_rx_frame(struct xgene_enet_desc_ring *rx_ring,
 	buf_pool->rx_skb[skb_index] = NULL;
 
 	datalen = xgene_enet_get_data_len(le64_to_cpu(raw_desc->m1));
+
+	/* strip off CRC as HW isn't doing this */
+	nv = GET_VAL(NV, le64_to_cpu(raw_desc->m0));
+	if (!nv)
+		datalen -= 4;
+
 	skb_put(skb, datalen);
 	prefetch(skb->data - NET_IP_ALIGN);
 	skb->protocol = eth_type_trans(skb, ndev);
@@ -717,10 +723,7 @@ static int xgene_enet_rx_frame(struct xgene_enet_desc_ring *rx_ring,
 		}
 	}
 
-	nv = GET_VAL(NV, le64_to_cpu(raw_desc->m0));
 	if (!nv) {
-		/* strip off CRC as HW isn't doing this */
-		datalen -= 4;
 		goto skip_jumbo;
 	}
 
-- 
2.34.1