Extract the PTP timestamp handling logic from ocelot_port_xmit() into a
separate ocelot_xmit_timestamp() helper function. This is a pure
refactor with no behavioral change.

The helper returns false if the skb was consumed (freed) due to a
timestamp request failure, and true if the caller should continue with
frame injection. The rew_op value is returned via pointer.

This prepares for splitting ocelot_port_xmit() into separate FDMA and
register injection paths in a subsequent patch.

Signed-off-by: Ziyi Guo <n7l8m4@u.northwestern.edu>
---
 drivers/net/ethernet/mscc/ocelot_net.c | 36 ++++++++++++++++----------
 1 file changed, 22 insertions(+), 14 deletions(-)

diff --git a/drivers/net/ethernet/mscc/ocelot_net.c b/drivers/net/ethernet/mscc/ocelot_net.c
index 469784d3a1a6..ef4a6c768de9 100644
--- a/drivers/net/ethernet/mscc/ocelot_net.c
+++ b/drivers/net/ethernet/mscc/ocelot_net.c
@@ -551,33 +551,41 @@ static int ocelot_port_stop(struct net_device *dev)
 	return 0;
 }
 
-static netdev_tx_t ocelot_port_xmit(struct sk_buff *skb, struct net_device *dev)
+static bool ocelot_xmit_timestamp(struct ocelot *ocelot, int port,
+				  struct sk_buff *skb, u32 *rew_op)
 {
-	struct ocelot_port_private *priv = netdev_priv(dev);
-	struct ocelot_port *ocelot_port = &priv->port;
-	struct ocelot *ocelot = ocelot_port->ocelot;
-	int port = priv->port.index;
-	u32 rew_op = 0;
-
-	if (!static_branch_unlikely(&ocelot_fdma_enabled) &&
-	    !ocelot_can_inject(ocelot, 0))
-		return NETDEV_TX_BUSY;
-
-	/* Check if timestamping is needed */
 	if (ocelot->ptp && (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)) {
 		struct sk_buff *clone = NULL;
 
 		if (ocelot_port_txtstamp_request(ocelot, port, skb, &clone)) {
 			kfree_skb(skb);
-			return NETDEV_TX_OK;
+			return false;
 		}
 
 		if (clone)
 			OCELOT_SKB_CB(skb)->clone = clone;
 
-		rew_op = ocelot_ptp_rew_op(skb);
+		*rew_op = ocelot_ptp_rew_op(skb);
 	}
 
+	return true;
+}
+
+static netdev_tx_t ocelot_port_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct ocelot_port_private *priv = netdev_priv(dev);
+	struct ocelot_port *ocelot_port = &priv->port;
+	struct ocelot *ocelot = ocelot_port->ocelot;
+	int port = priv->port.index;
+	u32 rew_op = 0;
+
+	if (!static_branch_unlikely(&ocelot_fdma_enabled) &&
+	    !ocelot_can_inject(ocelot, 0))
+		return NETDEV_TX_BUSY;
+
+	if (!ocelot_xmit_timestamp(ocelot, port, skb, &rew_op))
+		return NETDEV_TX_OK;
+
 	if (static_branch_unlikely(&ocelot_fdma_enabled)) {
 		ocelot_fdma_inject_frame(ocelot, port, rew_op, skb, dev);
 	} else {
-- 
2.34.1