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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jonathan Lemon <jonathan.lemon@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15 106/177] net: bcmgenet: hide status block before TX timestamping
Date:   Wed,  4 May 2022 18:44:59 +0200
Message-Id: <20220504153102.722994656@linuxfoundation.org>
In-Reply-To: <20220504153053.873100034@linuxfoundation.org>
References: <20220504153053.873100034@linuxfoundation.org>
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From: Jonathan Lemon <jonathan.lemon@gmail.com>

[ Upstream commit acac0541d1d65e81e599ec399d34d184d2424401 ]

The hardware checksum offloading requires use of a transmit
status block inserted before the outgoing frame data, this was
updated in '9a9ba2a4aaaa ("net: bcmgenet: always enable status blocks")'

However, skb_tx_timestamp() assumes that it is passed a raw frame
and PTP parsing chokes on this status block.

Fix this by calling __skb_pull(), which hides the TSB before calling
skb_tx_timestamp(), so an outgoing PTP packet is parsed correctly.

As the data in the skb has already been set up for DMA, and the
dma_unmap_* calls use a separately stored address, there is no
no effective change in the data transmission.

Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20220424165307.591145-1-jonathan.lemon@gmail.com
Fixes: d03825fba459 ("net: bcmgenet: add skb_tx_timestamp call")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/broadcom/genet/bcmgenet.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
index b4f99dd284e5..8bcc39b1575c 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
@@ -1991,6 +1991,11 @@ static struct sk_buff *bcmgenet_add_tsb(struct net_device *dev,
 	return skb;
 }
 
+static void bcmgenet_hide_tsb(struct sk_buff *skb)
+{
+	__skb_pull(skb, sizeof(struct status_64));
+}
+
 static netdev_tx_t bcmgenet_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct bcmgenet_priv *priv = netdev_priv(dev);
@@ -2097,6 +2102,8 @@ static netdev_tx_t bcmgenet_xmit(struct sk_buff *skb, struct net_device *dev)
 	}
 
 	GENET_CB(skb)->last_cb = tx_cb_ptr;
+
+	bcmgenet_hide_tsb(skb);
 	skb_tx_timestamp(skb);
 
 	/* Decrement total BD count and advance our write pointer */
-- 
2.35.1