[PATCH net-next v6 3/3] net: dsa: let user ports wait for a PHY that probes late

[Aleksei Sviridkin <f@lex.la>]

A user port connects its PHY once, when the switch sets up its ports.
If that PHY needs firmware from the host and its driver is a module not
loaded yet, the port gets no working PHY for the rest of the uptime.

Let a switch driver opt its user ports in to phylink waiting for such a
PHY, and opt in mt7530. Until the PHY attaches, .port_enable sees a NULL
phy, so the opt-in is per driver: qca8k dereferences that argument, and
gswip programs the PHY address from it at open, so a late attach leaves
it wrong until the next open. mt7530 does not use it. Shared ports are
left out.

Found on a Keenetic KN-1012 (MT7981B with an MT7531 switch), where the
EN8811H behind lan4 has its driver on the root filesystem and lan4 was
lost for the uptime.

Assisted-by: LLM
Signed-off-by: Aleksei Sviridkin <f@lex.la>
---
Changes in v6: the dsa.h comment says .port_enable must not use its
phy argument, rather than cope with a NULL one.

 drivers/net/dsa/mt7530.c | 1 +
 include/net/dsa.h        | 5 +++++
 net/dsa/user.c           | 1 +
 3 files changed, 7 insertions(+)

diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
index 7781a63b4e6f..e4c155605e27 100644
--- a/drivers/net/dsa/mt7530.c
+++ b/drivers/net/dsa/mt7530.c
@@ -3548,6 +3548,7 @@ mt7530_probe_common(struct mt7530_priv *priv)
 	priv->ds->priv = priv;
 	priv->ds->ops = &mt7530_switch_ops;
 	priv->ds->phylink_mac_ops = &mt753x_phylink_mac_ops;
+	priv->ds->phy_may_probe_late = true;
 	mutex_init(&priv->reg_mutex);
 	spin_lock_init(&priv->stats_lock);
 	INIT_DELAYED_WORK(&priv->stats_work, mt7530_stats_poll);
diff --git a/include/net/dsa.h b/include/net/dsa.h
index 5d12191b6f6f..04b151cd52ce 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -455,6 +455,11 @@ struct dsa_switch {
 	 */
 	u32			dscp_prio_mapping_is_global:1;
 
+	/* Drivers whose .port_enable does not use its phy argument may set
+	 * this to let user ports wait for a PHY that needs host firmware.
+	 */
+	u32			phy_may_probe_late:1;
+
 	/* Listener for switch fabric events */
 	struct notifier_block	nb;
 
diff --git a/net/dsa/user.c b/net/dsa/user.c
index 041f9060c8ef..41075bb74193 100644
--- a/net/dsa/user.c
+++ b/net/dsa/user.c
@@ -2661,6 +2661,7 @@ static int dsa_user_phy_setup(struct net_device *user_dev)
 
 	dp->pl_config.dev = &user_dev->dev;
 	dp->pl_config.type = PHYLINK_NETDEV;
+	dp->pl_config.phy_may_probe_late = ds->phy_may_probe_late;
 
 	/* The get_fixed_state callback takes precedence over polling the
 	 * link GPIO in PHYLINK (see phylink_get_fixed_state).  Only set
-- 
2.53.0