[PATCH net] net: bcmgenet: add hwtstamp callbacks to restore PHY timestamping

[James Clark <jjc@jclark.com>]

Hardware timestamp configuration fails with EOPNOTSUPP on BCMGENET
interfaces connected to a timestamp-capable PHY. On a Raspberry Pi
CM4, "hwstamp_ctl -i eth0 -t 1 -r 12" fails with "SIOCSHWTSTAMP failed:
Operation not supported", preventing ptp4l from using hardware
timestamping.

Commit 5062245a5a7f ("net: remove legacy way to get/set HW timestamp
config") removed the legacy ioctl fallback, assuming that all MAC
drivers supporting hardware timestamping implement ndo_hwtstamp_get()
and ndo_hwtstamp_set(), even when timestamping is provided only by
an attached PHY. BCMGENET does not implement these callbacks, so the
core rejects timestamp configuration requests before they reach
the PHY.

Add ndo_hwtstamp_get() and ndo_hwtstamp_set() callbacks so the core
can dispatch timestamp configuration requests through its phylib
helpers. Both callbacks return -EOPNOTSUPP because the MAC itself
does not support hardware timestamping; requests for the PHY are
handled by the core without invoking these callbacks.

Fixes: 5062245a5a7f ("net: remove legacy way to get/set HW timestamp config")
Assisted-by: LLM
Signed-off-by: James Clark <jjc@jclark.com>
---
 drivers/net/ethernet/broadcom/genet/bcmgenet.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
index a2305e642..8ead37ff9 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
@@ -3712,6 +3712,19 @@ static int bcmgenet_change_carrier(struct net_device *dev, bool new_carrier)
 	return 0;
 }
 
+static int bcmgenet_hwtstamp_get(struct net_device *dev,
+				 struct kernel_hwtstamp_config *cfg)
+{
+	return -EOPNOTSUPP;
+}
+
+static int bcmgenet_hwtstamp_set(struct net_device *dev,
+				 struct kernel_hwtstamp_config *cfg,
+				 struct netlink_ext_ack *extack)
+{
+	return -EOPNOTSUPP;
+}
+
 static const struct net_device_ops bcmgenet_netdev_ops = {
 	.ndo_open		= bcmgenet_open,
 	.ndo_stop		= bcmgenet_close,
@@ -3723,6 +3736,8 @@ static const struct net_device_ops bcmgenet_netdev_ops = {
 	.ndo_set_features	= bcmgenet_set_features,
 	.ndo_get_stats64	= bcmgenet_get_stats64,
 	.ndo_change_carrier	= bcmgenet_change_carrier,
+	.ndo_hwtstamp_get	= bcmgenet_hwtstamp_get,
+	.ndo_hwtstamp_set	= bcmgenet_hwtstamp_set,
 };
 
 /* GENET hardware parameters/characteristics */
-- 
2.55.0