net: sfp: add support for setting signalling rate

Add support to the SFP layer to allow phylink to set the signalling
rate for a SFP module. The rate given will be in units of kilo-baud
(1000 baud).
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/phylink.c

@@ -156,6 +156,23 @@ static const char *phylink_an_mode_str(unsigned int mode)
 	return mode < ARRAY_SIZE(modestr) ? modestr[mode] : "unknown";
 }
 
+static unsigned int phylink_interface_signal_rate(phy_interface_t interface)
+{
+	switch (interface) {
+	case PHY_INTERFACE_MODE_SGMII:
+	case PHY_INTERFACE_MODE_1000BASEX: /* 1.25Mbd */
+		return 1250;
+	case PHY_INTERFACE_MODE_2500BASEX: /* 3.125Mbd */
+		return 3125;
+	case PHY_INTERFACE_MODE_5GBASER: /* 5.15625Mbd */
+		return 5156;
+	case PHY_INTERFACE_MODE_10GBASER: /* 10.3125Mbd */
+		return 10313;
+	default:
+		return 0;
+	}
+}
+
 /**
  * phylink_interface_max_speed() - get the maximum speed of a phy interface
  * @interface: phy interface mode defined by &typedef phy_interface_t
@@ -1025,6 +1042,7 @@ static void phylink_major_config(struct phylink *pl, bool restart,
 {
 	struct phylink_pcs *pcs = NULL;
 	bool pcs_changed = false;
+	unsigned int rate_kbd;
 	int err;
 
 	phylink_dbg(pl, "major config %s\n", phy_modes(state->interface));
@@ -1084,6 +1102,12 @@ static void phylink_major_config(struct phylink *pl, bool restart,
 				    ERR_PTR(err));
 	}
 
+	if (pl->sfp_bus) {
+		rate_kbd = phylink_interface_signal_rate(state->interface);
+		if (rate_kbd)
+			sfp_upstream_set_signal_rate(pl->sfp_bus, rate_kbd);
+	}
+
 	phylink_pcs_poll_start(pl);
 }
 

drivers/net/phy/sfp-bus.c

@@ -575,6 +575,26 @@ static void sfp_upstream_clear(struct sfp_bus *bus)
 	bus->upstream = NULL;
 }
 
+/**
+ * sfp_upstream_set_signal_rate() - set data signalling rate
+ * @bus: a pointer to the &struct sfp_bus structure for the sfp module
+ * @rate_kbd: signalling rate in units of 1000 baud
+ *
+ * Configure the rate select settings on the SFP module for the signalling
+ * rate (not the same as the data rate).
+ *
+ * Locks that may be held:
+ *  Phylink's state_mutex
+ *  rtnl lock
+ *  SFP's sm_mutex
+ */
+void sfp_upstream_set_signal_rate(struct sfp_bus *bus, unsigned int rate_kbd)
+{
+	if (bus->registered)
+		bus->socket_ops->set_signal_rate(bus->sfp, rate_kbd);
+}
+EXPORT_SYMBOL_GPL(sfp_upstream_set_signal_rate);
+
 /**
  * sfp_bus_find_fwnode() - parse and locate the SFP bus from fwnode
  * @fwnode: firmware node for the parent device (MAC or PHY)

drivers/net/phy/sfp.c

@@ -2527,6 +2527,10 @@ static void sfp_stop(struct sfp *sfp)
 	sfp_sm_event(sfp, SFP_E_DEV_DOWN);
 }
 
+static void sfp_set_signal_rate(struct sfp *sfp, unsigned int rate_kbd)
+{
+}
+
 static int sfp_module_info(struct sfp *sfp, struct ethtool_modinfo *modinfo)
 {
 	/* locking... and check module is present */
@@ -2611,6 +2615,7 @@ static const struct sfp_socket_ops sfp_module_ops = {
 	.detach = sfp_detach,
 	.start = sfp_start,
 	.stop = sfp_stop,
+	.set_signal_rate = sfp_set_signal_rate,
 	.module_info = sfp_module_info,
 	.module_eeprom = sfp_module_eeprom,
 	.module_eeprom_by_page = sfp_module_eeprom_by_page,

drivers/net/phy/sfp.h

@@ -19,6 +19,7 @@ struct sfp_socket_ops {
 	void (*detach)(struct sfp *sfp);
 	void (*start)(struct sfp *sfp);
 	void (*stop)(struct sfp *sfp);
+	void (*set_signal_rate)(struct sfp *sfp, unsigned int rate_kbd);
 	int (*module_info)(struct sfp *sfp, struct ethtool_modinfo *modinfo);
 	int (*module_eeprom)(struct sfp *sfp, struct ethtool_eeprom *ee,
 			     u8 *data);

include/linux/sfp.h

@@ -556,6 +556,7 @@ int sfp_get_module_eeprom_by_page(struct sfp_bus *bus,
 				  struct netlink_ext_ack *extack);
 void sfp_upstream_start(struct sfp_bus *bus);
 void sfp_upstream_stop(struct sfp_bus *bus);
+void sfp_upstream_set_signal_rate(struct sfp_bus *bus, unsigned int rate_kbd);
 void sfp_bus_put(struct sfp_bus *bus);
 struct sfp_bus *sfp_bus_find_fwnode(const struct fwnode_handle *fwnode);
 int sfp_bus_add_upstream(struct sfp_bus *bus, void *upstream,
@@ -615,6 +616,11 @@ static inline void sfp_upstream_stop(struct sfp_bus *bus)
 {
 }
 
+static inline void sfp_upstream_set_signal_rate(struct sfp_bus *bus,
+						unsigned int rate_kbd)
+{
+}
+
 static inline void sfp_bus_put(struct sfp_bus *bus)
 {
 }