thunderbolt: Add support for XDomain connections

Two domains (hosts) can be connected through a Thunderbolt cable and in
that case they can start software services such as networking over the
high-speed DMA paths. Now that we have all the basic building blocks in
place to create DMA tunnels over the Thunderbolt fabric we can add this
support to the software connection manager as well.

Signed-off-by: Mika Westerberg <[e-mail]>

drivers/thunderbolt/switch.c

···
 	for (i = 0; i <= sw->config.max_port_number; i++) {
 		if (tb_port_has_remote(&sw->ports[i]))
 			tb_sw_set_unplugged(sw->ports[i].remote->sw);
+		else if (sw->ports[i].xdomain)
+			sw->ports[i].xdomain->is_unplugged = true;
 	}
 }
 
···
 	 */
 	if (tb_route(sw)) {
 		u64 uid;
+
+		/*
+		 * Check first that we can still read the switch config
+		 * space. It may be that there is now another domain
+		 * connected.
+		 */
+		err = tb_cfg_get_upstream_port(sw->tb->ctl, tb_route(sw));
+		if (err < 0) {
+			tb_sw_info(sw, "switch not present anymore\n");
+			return err;
+		}
 
 		err = tb_drom_read_uid_only(sw, &uid);
 		if (err) {
···
 	for (i = 1; i <= sw->config.max_port_number; i++) {
 		struct tb_port *port = &sw->ports[i];
 
-		if (!tb_port_has_remote(port))
+		if (!tb_port_has_remote(port) && !port->xdomain)
 			continue;
 
-		if (tb_wait_for_port(port, true) <= 0
-			|| tb_switch_resume(port->remote->sw)) {
+		if (tb_wait_for_port(port, true) <= 0) {
 			tb_port_warn(port,
 				     "lost during suspend, disconnecting\n");
-			tb_sw_set_unplugged(port->remote->sw);
+			if (tb_port_has_remote(port))
+				tb_sw_set_unplugged(port->remote->sw);
+			else if (port->xdomain)
+				port->xdomain->is_unplugged = true;
+		} else if (tb_port_has_remote(port)) {
+			if (tb_switch_resume(port->remote->sw)) {
+				tb_port_warn(port,
+					     "lost during suspend, disconnecting\n");
+				tb_sw_set_unplugged(port->remote->sw);
+			}
 		}
 	}
 	return 0;

drivers/thunderbolt/tb.c

···
 	}
 }
 
+static void tb_scan_xdomain(struct tb_port *port)
+{
+	struct tb_switch *sw = port->sw;
+	struct tb *tb = sw->tb;
+	struct tb_xdomain *xd;
+	u64 route;
+
+	route = tb_downstream_route(port);
+	xd = tb_xdomain_find_by_route(tb, route);
+	if (xd) {
+		tb_xdomain_put(xd);
+		return;
+	}
+
+	xd = tb_xdomain_alloc(tb, &sw->dev, route, tb->root_switch->uuid,
+			      NULL);
+	if (xd) {
+		tb_port_at(route, sw)->xdomain = xd;
+		tb_xdomain_add(xd);
+	}
+}
+
 static void tb_scan_port(struct tb_port *port);
 
 /**
···
 	if (tb_wait_for_port(port, false) <= 0)
 		return;
 	if (port->remote) {
-		tb_port_WARN(port, "port already has a remote!\n");
+		tb_port_dbg(port, "port already has a remote\n");
 		return;
 	}
 	sw = tb_switch_alloc(port->sw->tb, &port->sw->dev,
 			     tb_downstream_route(port));
-	if (IS_ERR(sw))
+	if (IS_ERR(sw)) {
+		/*
+		 * If there is an error accessing the connected switch
+		 * it may be connected to another domain. Also we allow
+		 * the other domain to be connected to a max depth switch.
+		 */
+		if (PTR_ERR(sw) == -EIO || PTR_ERR(sw) == -EADDRNOTAVAIL)
+			tb_scan_xdomain(port);
 		return;
+	}
 
 	if (tb_switch_configure(sw)) {
 		tb_switch_put(sw);
 		return;
+	}
+
+	/*
+	 * If there was previously another domain connected remove it
+	 * first.
+	 */
+	if (port->xdomain) {
+		tb_xdomain_remove(port->xdomain);
+		port->xdomain = NULL;
 	}
 
 	/*
···
 	return 0;
 }
 
+static int tb_approve_xdomain_paths(struct tb *tb, struct tb_xdomain *xd)
+{
+	struct tb_cm *tcm = tb_priv(tb);
+	struct tb_port *nhi_port, *dst_port;
+	struct tb_tunnel *tunnel;
+	struct tb_switch *sw;
+
+	sw = tb_to_switch(xd->dev.parent);
+	dst_port = tb_port_at(xd->route, sw);
+	nhi_port = tb_find_port(tb->root_switch, TB_TYPE_NHI);
+
+	mutex_lock(&tb->lock);
+	tunnel = tb_tunnel_alloc_dma(tb, nhi_port, dst_port, xd->transmit_ring,
+				     xd->transmit_path, xd->receive_ring,
+				     xd->receive_path);
+	if (!tunnel) {
+		mutex_unlock(&tb->lock);
+		return -ENOMEM;
+	}
+
+	if (tb_tunnel_activate(tunnel)) {
+		tb_port_info(nhi_port,
+			     "DMA tunnel activation failed, aborting\n");
+		tb_tunnel_free(tunnel);
+		mutex_unlock(&tb->lock);
+		return -EIO;
+	}
+
+	list_add_tail(&tunnel->list, &tcm->tunnel_list);
+	mutex_unlock(&tb->lock);
+	return 0;
+}
+
+static void __tb_disconnect_xdomain_paths(struct tb *tb, struct tb_xdomain *xd)
+{
+	struct tb_port *dst_port;
+	struct tb_switch *sw;
+
+	sw = tb_to_switch(xd->dev.parent);
+	dst_port = tb_port_at(xd->route, sw);
+
+	/*
+	 * It is possible that the tunnel was already teared down (in
+	 * case of cable disconnect) so it is fine if we cannot find it
+	 * here anymore.
+	 */
+	tb_free_tunnel(tb, TB_TUNNEL_DMA, NULL, dst_port);
+}
+
+static int tb_disconnect_xdomain_paths(struct tb *tb, struct tb_xdomain *xd)
+{
+	if (!xd->is_unplugged) {
+		mutex_lock(&tb->lock);
+		__tb_disconnect_xdomain_paths(tb, xd);
+		mutex_unlock(&tb->lock);
+	}
+	return 0;
+}
+
 /* hotplug handling */
 
 /**
···
 	}
 	if (ev->unplug) {
 		if (tb_port_has_remote(port)) {
-			tb_port_info(port, "unplugged\n");
+			tb_port_dbg(port, "switch unplugged\n");
 			tb_sw_set_unplugged(port->remote->sw);
 			tb_free_invalid_tunnels(tb);
 			tb_switch_remove(port->remote->sw);
 			port->remote = NULL;
 			if (port->dual_link_port)
 				port->dual_link_port->remote = NULL;
+		} else if (port->xdomain) {
+			struct tb_xdomain *xd = tb_xdomain_get(port->xdomain);
+
+			tb_port_dbg(port, "xdomain unplugged\n");
+			/*
+			 * Service drivers are unbound during
+			 * tb_xdomain_remove() so setting XDomain as
+			 * unplugged here prevents deadlock if they call
+			 * tb_xdomain_disable_paths(). We will tear down
+			 * the path below.
+			 */
+			xd->is_unplugged = true;
+			tb_xdomain_remove(xd);
+			port->xdomain = NULL;
+			__tb_disconnect_xdomain_paths(tb, xd);
+			tb_xdomain_put(xd);
 		} else if (tb_port_is_dpout(port)) {
 			tb_teardown_dp(tb, port);
 		} else {
···
 	struct tb_tunnel *n;
 
 	/* tunnels are only present after everything has been initialized */
-	list_for_each_entry_safe(tunnel, n, &tcm->tunnel_list, list)
+	list_for_each_entry_safe(tunnel, n, &tcm->tunnel_list, list) {
+		/*
+		 * DMA tunnels require the driver to be functional so we
+		 * tear them down. Other protocol tunnels can be left
+		 * intact.
+		 */
+		if (tb_tunnel_is_dma(tunnel))
+			tb_tunnel_deactivate(tunnel);
 		tb_tunnel_free(tunnel);
+	}
 	tb_switch_remove(tb->root_switch);
 	tcm->hotplug_active = false; /* signal tb_handle_hotplug to quit */
 }
···
 	return 0;
 }
 
+static int tb_free_unplugged_xdomains(struct tb_switch *sw)
+{
+	int i, ret = 0;
+
+	for (i = 1; i <= sw->config.max_port_number; i++) {
+		struct tb_port *port = &sw->ports[i];
+
+		if (tb_is_upstream_port(port))
+			continue;
+		if (port->xdomain && port->xdomain->is_unplugged) {
+			tb_xdomain_remove(port->xdomain);
+			port->xdomain = NULL;
+			ret++;
+		} else if (port->remote) {
+			ret += tb_free_unplugged_xdomains(port->remote->sw);
+		}
+	}
+
+	return ret;
+}
+
+static void tb_complete(struct tb *tb)
+{
+	/*
+	 * Release any unplugged XDomains and if there is a case where
+	 * another domain is swapped in place of unplugged XDomain we
+	 * need to run another rescan.
+	 */
+	mutex_lock(&tb->lock);
+	if (tb_free_unplugged_xdomains(tb->root_switch))
+		tb_scan_switch(tb->root_switch);
+	mutex_unlock(&tb->lock);
+}
+
 static const struct tb_cm_ops tb_cm_ops = {
 	.start = tb_start,
 	.stop = tb_stop,
 	.suspend_noirq = tb_suspend_noirq,
 	.resume_noirq = tb_resume_noirq,
+	.complete = tb_complete,
 	.handle_event = tb_handle_event,
 	.approve_switch = tb_tunnel_pci,
+	.approve_xdomain_paths = tb_approve_xdomain_paths,
+	.disconnect_xdomain_paths = tb_disconnect_xdomain_paths,
 };
 
 struct tb *tb_probe(struct tb_nhi *nhi)