thunderbolt: Scan for downstream switches

Add utility methods tb_port_state and tb_wait_for_port. Add
tb_scan_switch which recursively checks for downstream switches.
Signed-off-by: Andreas Noever <andreas.noever@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/thunderbolt/switch.c

@@ -52,6 +52,92 @@ static void tb_dump_port(struct tb *tb, struct tb_regs_port_header *port)
 	tb_info(tb, "  NFC Credits: %#x\n", port->nfc_credits);
 }
 
+/**
+ * tb_port_state() - get connectedness state of a port
+ *
+ * The port must have a TB_CAP_PHY (i.e. it should be a real port).
+ *
+ * Return: Returns an enum tb_port_state on success or an error code on failure.
+ */
+static int tb_port_state(struct tb_port *port)
+{
+	struct tb_cap_phy phy;
+	int res;
+	if (port->cap_phy == 0) {
+		tb_port_WARN(port, "does not have a PHY\n");
+		return -EINVAL;
+	}
+	res = tb_port_read(port, &phy, TB_CFG_PORT, port->cap_phy, 2);
+	if (res)
+		return res;
+	return phy.state;
+}
+
+/**
+ * tb_wait_for_port() - wait for a port to become ready
+ *
+ * Wait up to 1 second for a port to reach state TB_PORT_UP. If
+ * wait_if_unplugged is set then we also wait if the port is in state
+ * TB_PORT_UNPLUGGED (it takes a while for the device to be registered after
+ * switch resume). Otherwise we only wait if a device is registered but the link
+ * has not yet been established.
+ *
+ * Return: Returns an error code on failure. Returns 0 if the port is not
+ * connected or failed to reach state TB_PORT_UP within one second. Returns 1
+ * if the port is connected and in state TB_PORT_UP.
+ */
+int tb_wait_for_port(struct tb_port *port, bool wait_if_unplugged)
+{
+	int retries = 10;
+	int state;
+	if (!port->cap_phy) {
+		tb_port_WARN(port, "does not have PHY\n");
+		return -EINVAL;
+	}
+	if (tb_is_upstream_port(port)) {
+		tb_port_WARN(port, "is the upstream port\n");
+		return -EINVAL;
+	}
+
+	while (retries--) {
+		state = tb_port_state(port);
+		if (state < 0)
+			return state;
+		if (state == TB_PORT_DISABLED) {
+			tb_port_info(port, "is disabled (state: 0)\n");
+			return 0;
+		}
+		if (state == TB_PORT_UNPLUGGED) {
+			if (wait_if_unplugged) {
+				/* used during resume */
+				tb_port_info(port,
+					     "is unplugged (state: 7), retrying...\n");
+				msleep(100);
+				continue;
+			}
+			tb_port_info(port, "is unplugged (state: 7)\n");
+			return 0;
+		}
+		if (state == TB_PORT_UP) {
+			tb_port_info(port,
+				     "is connected, link is up (state: 2)\n");
+			return 1;
+		}
+
+		/*
+		 * After plug-in the state is TB_PORT_CONNECTING. Give it some
+		 * time.
+		 */
+		tb_port_info(port,
+			     "is connected, link is not up (state: %d), retrying...\n",
+			     state);
+		msleep(100);
+	}
+	tb_port_warn(port,
+		     "failed to reach state TB_PORT_UP. Ignoring port...\n");
+	return 0;
+}
+
 /**
  * tb_init_port() - initialize a port
  *
@@ -63,6 +149,7 @@ static void tb_dump_port(struct tb *tb, struct tb_regs_port_header *port)
 static int tb_init_port(struct tb_switch *sw, u8 port_nr)
 {
 	int res;
+	int cap;
 	struct tb_port *port = &sw->ports[port_nr];
 	port->sw = sw;
 	port->port = port_nr;
@@ -71,6 +158,16 @@ static int tb_init_port(struct tb_switch *sw, u8 port_nr)
 	if (res)
 		return res;
 
+	/* Port 0 is the switch itself and has no PHY. */
+	if (port->config.type == TB_TYPE_PORT && port_nr != 0) {
+		cap = tb_find_cap(port, TB_CFG_PORT, TB_CAP_PHY);
+
+		if (cap > 0)
+			port->cap_phy = cap;
+		else
+			tb_port_WARN(port, "non switch port without a PHY\n");
+	}
+
 	tb_dump_port(sw->tb, &port->config);
 
 	/* TODO: Read dual link port, DP port and more from EEPROM. */

drivers/thunderbolt/tb.c

@@ -11,6 +11,47 @@
 #include "tb.h"
 #include "tb_regs.h"
 
+
+/* enumeration & hot plug handling */
+
+
+static void tb_scan_port(struct tb_port *port);
+
+/**
+ * tb_scan_switch() - scan for and initialize downstream switches
+ */
+static void tb_scan_switch(struct tb_switch *sw)
+{
+	int i;
+	for (i = 1; i <= sw->config.max_port_number; i++)
+		tb_scan_port(&sw->ports[i]);
+}
+
+/**
+ * tb_scan_port() - check for and initialize switches below port
+ */
+static void tb_scan_port(struct tb_port *port)
+{
+	struct tb_switch *sw;
+	if (tb_is_upstream_port(port))
+		return;
+	if (port->config.type != TB_TYPE_PORT)
+		return;
+	if (tb_wait_for_port(port, false) <= 0)
+		return;
+	if (port->remote) {
+		tb_port_WARN(port, "port already has a remote!\n");
+		return;
+	}
+	sw = tb_switch_alloc(port->sw->tb, tb_downstream_route(port));
+	if (!sw)
+		return;
+	port->remote = tb_upstream_port(sw);
+	tb_upstream_port(sw)->remote = port;
+	tb_scan_switch(sw);
+}
+
+
 /* hotplug handling */
 
 struct tb_hotplug_event {
@@ -134,6 +175,9 @@ struct tb *thunderbolt_alloc_and_start(struct tb_nhi *nhi)
 	if (!tb->root_switch)
 		goto err_locked;
 
+	/* Full scan to discover devices added before the driver was loaded. */
+	tb_scan_switch(tb->root_switch);
+
 	/* Allow tb_handle_hotplug to progress events */
 	tb->hotplug_active = true;
 	mutex_unlock(&tb->lock);

drivers/thunderbolt/tb.h

@@ -29,6 +29,7 @@ struct tb_port {
 	struct tb_regs_port_header config;
 	struct tb_switch *sw;
 	struct tb_port *remote; /* remote port, NULL if not connected */
+	int cap_phy; /* offset, zero if not found */
 	u8 port; /* port number on switch */
 };
 
@@ -160,6 +161,8 @@ void thunderbolt_shutdown_and_free(struct tb *tb);
 struct tb_switch *tb_switch_alloc(struct tb *tb, u64 route);
 void tb_switch_free(struct tb_switch *sw);
 
+int tb_wait_for_port(struct tb_port *port, bool wait_if_unplugged);
+
 int tb_find_cap(struct tb_port *port, enum tb_cfg_space space, u32 value);
 
 
@@ -173,4 +176,17 @@ static inline bool tb_is_upstream_port(struct tb_port *port)
 	return port == tb_upstream_port(port->sw);
 }
 
+/**
+ * tb_downstream_route() - get route to downstream switch
+ *
+ * Port must not be the upstream port (otherwise a loop is created).
+ *
+ * Return: Returns a route to the switch behind @port.
+ */
+static inline u64 tb_downstream_route(struct tb_port *port)
+{
+	return tb_route(port->sw)
+	       | ((u64) port->port << (port->sw->config.depth * 8));
+}
+
 #endif