netdev - [PATCH net-next] net: dsa: don't call ptp_classify_raw() if switch doesn't provide RX timestamping

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Message-Id: <20221209175840.390707-1-vladimir.oltean@nxp.com>
Date:   Fri,  9 Dec 2022 19:58:40 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Richard Cochran <richardcochran@...il.com>
Subject: [PATCH net-next] net: dsa: don't call ptp_classify_raw() if switch doesn't provide RX timestamping

ptp_classify_raw() is not exactly cheap, since it invokes a BPF program
for every skb in the receive path. For switches which do not provide
ds->ops->port_rxtstamp(), running ptp_classify_raw() provides precisely
nothing, so check for the presence of the function pointer first, since
that is much cheaper.

Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
 net/dsa/tag.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/dsa/tag.c b/net/dsa/tag.c
index 383721e167d6..b2fba1a003ce 100644
--- a/net/dsa/tag.c
+++ b/net/dsa/tag.c
@@ -33,6 +33,9 @@ static bool dsa_skb_defer_rx_timestamp(struct dsa_slave_priv *p,
 	struct dsa_switch *ds = p->dp->ds;
 	unsigned int type;
 
+	if (!ds->ops->port_rxtstamp)
+		return false;
+
 	if (skb_headroom(skb) < ETH_HLEN)
 		return false;
 
@@ -45,10 +48,7 @@ static bool dsa_skb_defer_rx_timestamp(struct dsa_slave_priv *p,
 	if (type == PTP_CLASS_NONE)
 		return false;
 
-	if (likely(ds->ops->port_rxtstamp))
-		return ds->ops->port_rxtstamp(ds, p->dp->index, skb, type);
-
-	return false;
+	return ds->ops->port_rxtstamp(ds, p->dp->index, skb, type);
 }
 
 static int dsa_switch_rcv(struct sk_buff *skb, struct net_device *dev,
-- 
2.34.1