net: mscc: ocelot: install MAC addresses in .ndo_set_rx_mode from process context

Currently ocelot_set_rx_mode calls ocelot_mact_learn directly, which has
a very nice ocelot_mact_wait_for_completion at the end. Introduced in
commit 639c1b2625 ("net: mscc: ocelot: Register poll timeout should be
wall time not attempts"), this function uses readx_poll_timeout which
triggers a lot of lockdep warnings and is also dangerous to use from
atomic context, potentially leading to lockups and panics.

Steen Hegelund added a poll timeout of 100 ms for checking the MAC
table, a duration which is clearly absurd to poll in atomic context.
So we need to defer the MAC table access to process context, which we do
via a dynamically allocated workqueue which contains all there is to
know about the MAC table operation it has to do.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20201212191612.222019-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mscc/ocelot.c

@@ -1513,6 +1513,12 @@ int ocelot_init(struct ocelot *ocelot)
 	if (!ocelot->stats_queue)
 		return -ENOMEM;
 
+	ocelot->owq = alloc_ordered_workqueue("ocelot-owq", 0);
+	if (!ocelot->owq) {
+		destroy_workqueue(ocelot->stats_queue);
+		return -ENOMEM;
+	}
+
 	INIT_LIST_HEAD(&ocelot->multicast);
 	INIT_LIST_HEAD(&ocelot->pgids);
 	ocelot_mact_init(ocelot);
@@ -1619,6 +1625,7 @@ void ocelot_deinit(struct ocelot *ocelot)
 {
 	cancel_delayed_work(&ocelot->stats_work);
 	destroy_workqueue(ocelot->stats_queue);
+	destroy_workqueue(ocelot->owq);
 	mutex_destroy(&ocelot->stats_lock);
 }
 EXPORT_SYMBOL(ocelot_deinit);

drivers/net/ethernet/mscc/ocelot_net.c

@@ -414,13 +414,81 @@ static int ocelot_port_xmit(struct sk_buff *skb, struct net_device *dev)
 	return NETDEV_TX_OK;
 }
 
+enum ocelot_action_type {
+	OCELOT_MACT_LEARN,
+	OCELOT_MACT_FORGET,
+};
+
+struct ocelot_mact_work_ctx {
+	struct work_struct work;
+	struct ocelot *ocelot;
+	enum ocelot_action_type type;
+	union {
+		/* OCELOT_MACT_LEARN */
+		struct {
+			unsigned char addr[ETH_ALEN];
+			u16 vid;
+			enum macaccess_entry_type entry_type;
+			int pgid;
+		} learn;
+		/* OCELOT_MACT_FORGET */
+		struct {
+			unsigned char addr[ETH_ALEN];
+			u16 vid;
+		} forget;
+	};
+};
+
+#define ocelot_work_to_ctx(x) \
+	container_of((x), struct ocelot_mact_work_ctx, work)
+
+static void ocelot_mact_work(struct work_struct *work)
+{
+	struct ocelot_mact_work_ctx *w = ocelot_work_to_ctx(work);
+	struct ocelot *ocelot = w->ocelot;
+
+	switch (w->type) {
+	case OCELOT_MACT_LEARN:
+		ocelot_mact_learn(ocelot, w->learn.pgid, w->learn.addr,
+				  w->learn.vid, w->learn.entry_type);
+		break;
+	case OCELOT_MACT_FORGET:
+		ocelot_mact_forget(ocelot, w->forget.addr, w->forget.vid);
+		break;
+	default:
+		break;
+	};
+
+	kfree(w);
+}
+
+static int ocelot_enqueue_mact_action(struct ocelot *ocelot,
+				      const struct ocelot_mact_work_ctx *ctx)
+{
+	struct ocelot_mact_work_ctx *w = kmemdup(ctx, sizeof(*w), GFP_ATOMIC);
+
+	if (!w)
+		return -ENOMEM;
+
+	w->ocelot = ocelot;
+	INIT_WORK(&w->work, ocelot_mact_work);
+	queue_work(ocelot->owq, &w->work);
+
+	return 0;
+}
+
 static int ocelot_mc_unsync(struct net_device *dev, const unsigned char *addr)
 {
 	struct ocelot_port_private *priv = netdev_priv(dev);
 	struct ocelot_port *ocelot_port = &priv->port;
 	struct ocelot *ocelot = ocelot_port->ocelot;
+	struct ocelot_mact_work_ctx w;
 
-	return ocelot_mact_forget(ocelot, addr, ocelot_port->pvid_vlan.vid);
+	ether_addr_copy(w.forget.addr, addr);
+	w.forget.vid = ocelot_port->pvid_vlan.vid;
+	w.type = OCELOT_MACT_FORGET;
+
+	return ocelot_enqueue_mact_action(ocelot, &w);
 }
 
 static int ocelot_mc_sync(struct net_device *dev, const unsigned char *addr)
@@ -428,9 +496,15 @@ static int ocelot_mc_sync(struct net_device *dev, const unsigned char *addr)
 	struct ocelot_port_private *priv = netdev_priv(dev);
 	struct ocelot_port *ocelot_port = &priv->port;
 	struct ocelot *ocelot = ocelot_port->ocelot;
+	struct ocelot_mact_work_ctx w;
 
-	return ocelot_mact_learn(ocelot, PGID_CPU, addr,
-				 ocelot_port->pvid_vlan.vid, ENTRYTYPE_LOCKED);
+	ether_addr_copy(w.learn.addr, addr);
+	w.learn.vid = ocelot_port->pvid_vlan.vid;
+	w.learn.pgid = PGID_CPU;
+	w.learn.entry_type = ENTRYTYPE_LOCKED;
+	w.type = OCELOT_MACT_LEARN;
+
+	return ocelot_enqueue_mact_action(ocelot, &w);
 }
 
 static void ocelot_set_rx_mode(struct net_device *dev)

include/soc/mscc/ocelot.h

@@ -650,6 +650,8 @@ struct ocelot {
 	struct delayed_work		stats_work;
 	struct workqueue_struct		*stats_queue;
 
+	struct workqueue_struct		*owq;
+
 	u8				ptp:1;
 	struct ptp_clock		*ptp_clock;
 	struct ptp_clock_info		ptp_info;