From: Russell King <rmk+kernel@armlinux.org.uk>
Date: Fri, 8 Nov 2019 17:39:29 +0000
Subject: net: sfp: rework upstream interface
Patch-mainline: v5.5-rc1
Git-commit: 727b3668b730634228fc65c336c2a7a080e02885
References: bsc#1154353

The current upstream interface is an all-or-nothing, which is
sub-optimal for future changes, as it doesn't allow the upstream driver
to prepare for the SFP module becoming available, as it is at boot.

Switch to a find-sfp-bus, add-upstream, del-upstream, put-sfp-bus
interface structure instead, which allows the upstream driver to
prepare for a module being available as soon as add-upstream is called.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/phy/phylink.c |   10 +++--
 drivers/net/phy/sfp-bus.c |   92 ++++++++++++++++++++++++++++++++--------------
 include/linux/sfp.h       |   25 ++++++++----
 3 files changed, 88 insertions(+), 39 deletions(-)

--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -567,7 +567,7 @@ static int phylink_register_sfp(struct p
 	struct sfp_bus *bus;
 	int ret;
 
-	bus = sfp_register_upstream_node(fwnode, pl, &sfp_phylink_ops);
+	bus = sfp_bus_find_fwnode(fwnode);
 	if (IS_ERR(bus)) {
 		ret = PTR_ERR(bus);
 		phylink_err(pl, "unable to attach SFP bus: %d\n", ret);
@@ -576,7 +576,10 @@ static int phylink_register_sfp(struct p
 
 	pl->sfp_bus = bus;
 
-	return 0;
+	ret = sfp_bus_add_upstream(bus, pl, &sfp_phylink_ops);
+	sfp_bus_put(bus);
+
+	return ret;
 }
 
 /**
@@ -674,8 +677,7 @@ EXPORT_SYMBOL_GPL(phylink_create);
  */
 void phylink_destroy(struct phylink *pl)
 {
-	if (pl->sfp_bus)
-		sfp_unregister_upstream(pl->sfp_bus);
+	sfp_bus_del_upstream(pl->sfp_bus);
 	if (pl->link_gpio)
 		gpiod_put(pl->link_gpio);
 
--- a/drivers/net/phy/sfp-bus.c
+++ b/drivers/net/phy/sfp-bus.c
@@ -329,10 +329,19 @@ static void sfp_bus_release(struct kref
 	kfree(bus);
 }
 
-static void sfp_bus_put(struct sfp_bus *bus)
+/**
+ * sfp_bus_put() - put a reference on the &struct sfp_bus
+ * bus: the &struct sfp_bus found via sfp_bus_find_fwnode()
+ *
+ * Put a reference on the &struct sfp_bus and free the underlying structure
+ * if this was the last reference.
+ */
+void sfp_bus_put(struct sfp_bus *bus)
 {
-	kref_put_mutex(&bus->kref, sfp_bus_release, &sfp_mutex);
+	if (bus)
+		kref_put_mutex(&bus->kref, sfp_bus_release, &sfp_mutex);
 }
+EXPORT_SYMBOL_GPL(sfp_bus_put);
 
 static int sfp_register_bus(struct sfp_bus *bus)
 {
@@ -348,11 +357,11 @@ static int sfp_register_bus(struct sfp_b
 				return ret;
 		}
 	}
+	bus->registered = true;
 	bus->socket_ops->attach(bus->sfp);
 	if (bus->started)
 		bus->socket_ops->start(bus->sfp);
 	bus->upstream_ops->attach(bus->upstream, bus);
-	bus->registered = true;
 	return 0;
 }
 
@@ -446,13 +455,12 @@ static void sfp_upstream_clear(struct sf
 }
 
 /**
- * sfp_register_upstream_node() - parse and register the neighbouring device
+ * sfp_bus_find_fwnode() - parse and locate the SFP bus from fwnode
  * @fwnode: firmware node for the parent device (MAC or PHY)
- * @upstream: the upstream private data
- * @ops: the upstream's &struct sfp_upstream_ops
  *
- * Parse the parent device's firmware node for a SFP bus, and register the
- * SFP bus using sfp_register_upstream().
+ * Parse the parent device's firmware node for a SFP bus, and locate
+ * the sfp_bus structure, incrementing its reference count.  This must
+ * be put via sfp_bus_put() when done.
  *
  * Returns: on success, a pointer to the sfp_bus structure,
  *	    %NULL if no SFP is specified,
@@ -462,9 +470,7 @@ static void sfp_upstream_clear(struct sf
  * 	        %-ENOMEM if we failed to allocate the bus.
  *		an error from the upstream's connect_phy() method.
  */
-struct sfp_bus *sfp_register_upstream_node(struct fwnode_handle *fwnode,
-					   void *upstream,
-					   const struct sfp_upstream_ops *ops)
+struct sfp_bus *sfp_bus_find_fwnode(struct fwnode_handle *fwnode)
 {
 	struct fwnode_reference_args ref;
 	struct sfp_bus *bus;
@@ -482,7 +488,39 @@ struct sfp_bus *sfp_register_upstream_no
 	if (!bus)
 		return ERR_PTR(-ENOMEM);
 
+	return bus;
+}
+EXPORT_SYMBOL_GPL(sfp_bus_find_fwnode);
+
+/**
+ * sfp_bus_add_upstream() - parse and register the neighbouring device
+ * @bus: the &struct sfp_bus found via sfp_bus_find_fwnode()
+ * @upstream: the upstream private data
+ * @ops: the upstream's &struct sfp_upstream_ops
+ *
+ * Add upstream driver for the SFP bus, and if the bus is complete, register
+ * the SFP bus using sfp_register_upstream().  This takes a reference on the
+ * bus, so it is safe to put the bus after this call.
+ *
+ * Returns: on success, a pointer to the sfp_bus structure,
+ *	    %NULL if no SFP is specified,
+ * 	    on failure, an error pointer value:
+ * 		corresponding to the errors detailed for
+ * 		fwnode_property_get_reference_args().
+ * 	        %-ENOMEM if we failed to allocate the bus.
+ *		an error from the upstream's connect_phy() method.
+ */
+int sfp_bus_add_upstream(struct sfp_bus *bus, void *upstream,
+			 const struct sfp_upstream_ops *ops)
+{
+	int ret;
+
+	/* If no bus, return success */
+	if (!bus)
+		return 0;
+
 	rtnl_lock();
+	kref_get(&bus->kref);
 	bus->upstream_ops = ops;
 	bus->upstream = upstream;
 
@@ -495,33 +533,33 @@ struct sfp_bus *sfp_register_upstream_no
 	}
 	rtnl_unlock();
 
-	if (ret) {
+	if (ret)
 		sfp_bus_put(bus);
-		bus = ERR_PTR(ret);
-	}
 
-	return bus;
+	return ret;
 }
-EXPORT_SYMBOL_GPL(sfp_register_upstream_node);
+EXPORT_SYMBOL_GPL(sfp_bus_add_upstream);
 
 /**
- * sfp_unregister_upstream() - Unregister sfp bus
+ * sfp_bus_del_upstream() - Delete a sfp bus
  * @bus: a pointer to the &struct sfp_bus structure for the sfp module
  *
- * Unregister a previously registered upstream connection for the SFP
- * module. @bus is returned from sfp_register_upstream().
+ * Delete a previously registered upstream connection for the SFP
+ * module. @bus should have been added by sfp_bus_add_upstream().
  */
-void sfp_unregister_upstream(struct sfp_bus *bus)
+void sfp_bus_del_upstream(struct sfp_bus *bus)
 {
-	rtnl_lock();
-	if (bus->sfp)
-		sfp_unregister_bus(bus);
-	sfp_upstream_clear(bus);
-	rtnl_unlock();
+	if (bus) {
+		rtnl_lock();
+		if (bus->sfp)
+			sfp_unregister_bus(bus);
+		sfp_upstream_clear(bus);
+		rtnl_unlock();
 
-	sfp_bus_put(bus);
+		sfp_bus_put(bus);
+	}
 }
-EXPORT_SYMBOL_GPL(sfp_unregister_upstream);
+EXPORT_SYMBOL_GPL(sfp_bus_del_upstream);
 
 /* Socket driver entry points */
 int sfp_add_phy(struct sfp_bus *bus, struct phy_device *phydev)
--- a/include/linux/sfp.h
+++ b/include/linux/sfp.h
@@ -508,10 +508,11 @@ int sfp_get_module_eeprom(struct sfp_bus
 			  u8 *data);
 void sfp_upstream_start(struct sfp_bus *bus);
 void sfp_upstream_stop(struct sfp_bus *bus);
-struct sfp_bus *sfp_register_upstream_node(struct fwnode_handle *fwnode,
-					   void *upstream,
-					   const struct sfp_upstream_ops *ops);
-void sfp_unregister_upstream(struct sfp_bus *bus);
+void sfp_bus_put(struct sfp_bus *bus);
+struct sfp_bus *sfp_bus_find_fwnode(struct fwnode_handle *fwnode);
+int sfp_bus_add_upstream(struct sfp_bus *bus, void *upstream,
+			 const struct sfp_upstream_ops *ops);
+void sfp_bus_del_upstream(struct sfp_bus *bus);
 #else
 static inline int sfp_parse_port(struct sfp_bus *bus,
 				 const struct sfp_eeprom_id *id,
@@ -553,14 +554,22 @@ static inline void sfp_upstream_stop(str
 {
 }
 
-static inline struct sfp_bus *sfp_register_upstream_node(
-	struct fwnode_handle *fwnode, void *upstream,
-	const struct sfp_upstream_ops *ops)
+static inline void sfp_bus_put(struct sfp_bus *bus)
+{
+}
+
+static inline struct sfp_bus *sfp_bus_find_fwnode(struct fwnode_handle *fwnode)
 {
 	return NULL;
 }
 
-static inline void sfp_unregister_upstream(struct sfp_bus *bus)
+static int sfp_bus_add_upstream(struct sfp_bus *bus, void *upstream,
+				const struct sfp_upstream_ops *ops)
+{
+	return 0;
+}
+
+static inline void sfp_bus_del_upstream(struct sfp_bus *bus)
 {
 }
 #endif