netdev - [PATCH net v2 2/2] gianfar: Account for Tx PTP timestamp in the skb headroom

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Date:   Thu, 29 Oct 2020 10:10:57 +0200
From:   Claudiu Manoil <claudiu.manoil@....com>
To:     netdev@...r.kernel.org
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, james.jurack@...tek.com
Subject: [PATCH net v2 2/2] gianfar: Account for Tx PTP timestamp in the skb headroom

When PTP timestamping is enabled on Tx, the controller
inserts the Tx timestamp at the beginning of the frame
buffer, between SFD and the L2 frame header.  This means
that the skb provided by the stack is required to have
enough headroom otherwise it needs to be reallocated.
This patch is requesting enough headroom from the stack to
accommodate PTP frames in order to avoid reallocation whenever
possible.
There's no reason not to set needed_headroom to a large enough
value to accommodate PTP frames, so in this regard this patch
is a fix.

Fixes: bee9e58c9e98 ("gianfar:don't add FCB length to hard_header_len")
Signed-off-by: Claudiu Manoil <claudiu.manoil@....com>
---
v2: rephrased message after adding patch 1/2

 drivers/net/ethernet/freescale/gianfar.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index 7b735fe65334..d391a45cebb6 100644
--- a/drivers/net/ethernet/freescale/gianfar.c
+++ b/drivers/net/ethernet/freescale/gianfar.c
@@ -3372,7 +3372,7 @@ static int gfar_probe(struct platform_device *ofdev)

 	if (dev->features & NETIF_F_IP_CSUM ||
 	    priv->device_flags & FSL_GIANFAR_DEV_HAS_TIMER)
-		dev->needed_headroom = GMAC_FCB_LEN;
+		dev->needed_headroom = GMAC_FCB_LEN + GMAC_TXPAL_LEN;

 	/* Initializing some of the rx/tx queue level parameters */
 	for (i = 0; i < priv->num_tx_queues; i++) {
-- 
2.17.1