[v2,net-next,08/12] net: dsa: tag_ocelot: single out PTP-related transmit tag processing

Commit Message

Vladimir Oltean Feb. 13, 2021, 10:37 p.m. UTC

From: Vladimir Oltean <[e-mail]>

There is one place where we cannot avoid accessing driver data, and that
is 2-step PTP TX timestamping, since the switch wants us to provide a
timestamp request ID through the injection header, which naturally must
come from a sequence number kept by the driver (it is generated by the
.port_txtstamp method prior to the tagger's xmit).

However, since other drivers like dsa_loop do not claim PTP support
anyway, the DSA_SKB_CB(skb)->clone will always be NULL anyway, so if we
move all PTP-related dereferences of struct ocelot and struct ocelot_port
into a separate function, we can effectively ensure that this is dead
code when the ocelot tagger is attached to non-ocelot switches, and the
stateful portion of the tagger is more self-contained.

Signed-off-by: Vladimir Oltean <[e-mail]>
---
Changes in v2:
None.

 net/dsa/tag_ocelot.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

Comments

Florian Fainelli Feb. 14, 2021, 1:26 a.m. UTC | #1

On 2/13/2021 14:37, Vladimir Oltean wrote:
> From: Vladimir Oltean <[e-mail]>
> 
> There is one place where we cannot avoid accessing driver data, and that
> is 2-step PTP TX timestamping, since the switch wants us to provide a
> timestamp request ID through the injection header, which naturally must
> come from a sequence number kept by the driver (it is generated by the
> .port_txtstamp method prior to the tagger's xmit).
> 
> However, since other drivers like dsa_loop do not claim PTP support
> anyway, the DSA_SKB_CB(skb)->clone will always be NULL anyway, so if we
> move all PTP-related dereferences of struct ocelot and struct ocelot_port
> into a separate function, we can effectively ensure that this is dead
> code when the ocelot tagger is attached to non-ocelot switches, and the
> stateful portion of the tagger is more self-contained.
> 
> Signed-off-by: Vladimir Oltean <[e-mail]>

Reviewed-by: Florian Fainelli <[e-mail]>

Patch

diff --git a/net/dsa/tag_ocelot.c b/net/dsa/tag_ocelot.c
index 8ce0b26f3520..fe00519229d7 100644
--- a/net/dsa/tag_ocelot.c
+++ b/net/dsa/tag_ocelot.c
@@ -5,6 +5,25 @@ 
 #include <soc/mscc/ocelot.h>
 #include "dsa_priv.h"
 
+static void ocelot_xmit_ptp(struct dsa_port *dp, void *injection,
+			    struct sk_buff *clone)
+{
+	struct ocelot *ocelot = dp->ds->priv;
+	struct ocelot_port *ocelot_port;
+	u64 rew_op;
+
+	ocelot_port = ocelot->ports[dp->index];
+	rew_op = ocelot_port->ptp_cmd;
+
+	/* Retrieve timestamp ID populated inside skb->cb[0] of the
+	 * clone by ocelot_port_add_txtstamp_skb
+	 */
+	if (ocelot_port->ptp_cmd == IFH_REW_OP_TWO_STEP_PTP)
+		rew_op |= clone->cb[0] << 3;
+
+	ocelot_ifh_set_rew_op(injection, rew_op);
+}
+
 static struct sk_buff *ocelot_xmit(struct sk_buff *skb,
 				   struct net_device *netdev)
 {
@@ -29,17 +48,8 @@  static struct sk_buff *ocelot_xmit(struct sk_buff *skb,
 	ocelot_ifh_set_qos_class(injection, skb->priority);
 
 	/* TX timestamping was requested */
-	if (clone) {
-		u64 rew_op = ocelot_port->ptp_cmd;
-
-		/* Retrieve timestamp ID populated inside skb->cb[0] of the
-		 * clone by ocelot_port_add_txtstamp_skb
-		 */
-		if (ocelot_port->ptp_cmd == IFH_REW_OP_TWO_STEP_PTP)
-			rew_op |= clone->cb[0] << 3;
-
-		ocelot_ifh_set_rew_op(injection, rew_op);
-	}
+	if (clone)
+		ocelot_xmit_ptp(dp, injection, clone);
 
 	return skb;
 }