thunderbolt: Add USB3 bandwidth management

USB3 supports both isochronous and non-isochronous traffic. The former
requires guaranteed bandwidth and can take up to 90% of the total
bandwidth. With USB4 USB3 is tunneled over USB4 fabric which means that
we need to make sure there is enough bandwidth allocated for the USB3
tunnels in addition to DisplayPort tunnels.

Whereas DisplayPort bandwidth management is static and done before the
DP tunnel is established, the USB3 bandwidth management is dynamic and
allows increasing and decreasing the allocated bandwidth according to
what is currently consumed. This is done through host router USB3
downstream adapter registers.

This adds USB3 bandwidth management to the software connection manager
so that we always try to allocate maximum bandwidth for DP tunnels and
what is left is allocated for USB3.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

1 files changed, 257 insertions, 83 deletions

diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index 53f9673c1395..bbcf0f25617c 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -216,9 +216,187 @@ static struct tb_port *tb_find_usb3_down(struct tb_switch *sw,
 	return NULL;
 }
 
+static struct tb_tunnel *tb_find_tunnel(struct tb *tb, enum tb_tunnel_type type,
+					struct tb_port *src_port,
+					struct tb_port *dst_port)
+{
+	struct tb_cm *tcm = tb_priv(tb);
+	struct tb_tunnel *tunnel;
+
+	list_for_each_entry(tunnel, &tcm->tunnel_list, list) {
+		if (tunnel->type == type &&
+		    ((src_port && src_port == tunnel->src_port) ||
+		     (dst_port && dst_port == tunnel->dst_port))) {
+			return tunnel;
+		}
+	}
+
+	return NULL;
+}
+
+static struct tb_tunnel *tb_find_first_usb3_tunnel(struct tb *tb,
+						   struct tb_port *src_port,
+						   struct tb_port *dst_port)
+{
+	struct tb_port *port, *usb3_down;
+	struct tb_switch *sw;
+
+	/* Pick the router that is deepest in the topology */
+	if (dst_port->sw->config.depth > src_port->sw->config.depth)
+		sw = dst_port->sw;
+	else
+		sw = src_port->sw;
+
+	/* Can't be the host router */
+	if (sw == tb->root_switch)
+		return NULL;
+
+	/* Find the downstream USB4 port that leads to this router */
+	port = tb_port_at(tb_route(sw), tb->root_switch);
+	/* Find the corresponding host router USB3 downstream port */
+	usb3_down = usb4_switch_map_usb3_down(tb->root_switch, port);
+	if (!usb3_down)
+		return NULL;
+
+	return tb_find_tunnel(tb, TB_TUNNEL_USB3, usb3_down, NULL);
+}
+
+static int tb_available_bandwidth(struct tb *tb, struct tb_port *src_port,
+	struct tb_port *dst_port, int *available_up, int *available_down)
+{
+	int usb3_consumed_up, usb3_consumed_down, ret;
+	struct tb_cm *tcm = tb_priv(tb);
+	struct tb_tunnel *tunnel;
+	struct tb_port *port;
+
+	tb_port_dbg(dst_port, "calculating available bandwidth\n");
+
+	tunnel = tb_find_first_usb3_tunnel(tb, src_port, dst_port);
+	if (tunnel) {
+		ret = tb_tunnel_consumed_bandwidth(tunnel, &usb3_consumed_up,
+						   &usb3_consumed_down);
+		if (ret)
+			return ret;
+	} else {
+		usb3_consumed_up = 0;
+		usb3_consumed_down = 0;
+	}
+
+	*available_up = *available_down = 40000;
+
+	/* Find the minimum available bandwidth over all links */
+	tb_for_each_port_on_path(src_port, dst_port, port) {
+		int link_speed, link_width, up_bw, down_bw;
+
+		if (!tb_port_is_null(port))
+			continue;
+
+		if (tb_is_upstream_port(port)) {
+			link_speed = port->sw->link_speed;
+		} else {
+			link_speed = tb_port_get_link_speed(port);
+			if (link_speed < 0)
+				return link_speed;
+		}
+
+		link_width = port->bonded ? 2 : 1;
+
+		up_bw = link_speed * link_width * 1000; /* Mb/s */
+		/* Leave 10% guard band */
+		up_bw -= up_bw / 10;
+		down_bw = up_bw;
+
+		tb_port_dbg(port, "link total bandwidth %d Mb/s\n", up_bw);
+
+		/*
+		 * Find all DP tunnels that cross the port and reduce
+		 * their consumed bandwidth from the available.
+		 */
+		list_for_each_entry(tunnel, &tcm->tunnel_list, list) {
+			int dp_consumed_up, dp_consumed_down;
+
+			if (!tb_tunnel_is_dp(tunnel))
+				continue;
+
+			if (!tb_tunnel_port_on_path(tunnel, port))
+				continue;
+
+			ret = tb_tunnel_consumed_bandwidth(tunnel,
+							   &dp_consumed_up,
+							   &dp_consumed_down);
+			if (ret)
+				return ret;
+
+			up_bw -= dp_consumed_up;
+			down_bw -= dp_consumed_down;
+		}
+
+		/*
+		 * If USB3 is tunneled from the host router down to the
+		 * branch leading to port we need to take USB3 consumed
+		 * bandwidth into account regardless whether it actually
+		 * crosses the port.
+		 */
+		up_bw -= usb3_consumed_up;
+		down_bw -= usb3_consumed_down;
+
+		if (up_bw < *available_up)
+			*available_up = up_bw;
+		if (down_bw < *available_down)
+			*available_down = down_bw;
+	}
+
+	if (*available_up < 0)
+		*available_up = 0;
+	if (*available_down < 0)
+		*available_down = 0;
+
+	return 0;
+}
+
+static int tb_release_unused_usb3_bandwidth(struct tb *tb,
+					    struct tb_port *src_port,
+					    struct tb_port *dst_port)
+{
+	struct tb_tunnel *tunnel;
+
+	tunnel = tb_find_first_usb3_tunnel(tb, src_port, dst_port);
+	return tunnel ? tb_tunnel_release_unused_bandwidth(tunnel) : 0;
+}
+
+static void tb_reclaim_usb3_bandwidth(struct tb *tb, struct tb_port *src_port,
+				      struct tb_port *dst_port)
+{
+	int ret, available_up, available_down;
+	struct tb_tunnel *tunnel;
+
+	tunnel = tb_find_first_usb3_tunnel(tb, src_port, dst_port);
+	if (!tunnel)
+		return;
+
+	tb_dbg(tb, "reclaiming unused bandwidth for USB3\n");
+
+	/*
+	 * Calculate available bandwidth for the first hop USB3 tunnel.
+	 * That determines the whole USB3 bandwidth for this branch.
+	 */
+	ret = tb_available_bandwidth(tb, tunnel->src_port, tunnel->dst_port,
+				     &available_up, &available_down);
+	if (ret) {
+		tb_warn(tb, "failed to calculate available bandwidth\n");
+		return;
+	}
+
+	tb_dbg(tb, "available bandwidth for USB3 %d/%d Mb/s\n",
+	       available_up, available_down);
+
+	tb_tunnel_reclaim_available_bandwidth(tunnel, &available_up, &available_down);
+}
+
 static int tb_tunnel_usb3(struct tb *tb, struct tb_switch *sw)
 {
 	struct tb_switch *parent = tb_switch_parent(sw);
+	int ret, available_up, available_down;
 	struct tb_port *up, *down, *port;
 	struct tb_cm *tcm = tb_priv(tb);
 	struct tb_tunnel *tunnel;
@@ -249,21 +427,48 @@ static int tb_tunnel_usb3(struct tb *tb, struct tb_switch *sw)
 		parent_up = tb_switch_find_port(parent, TB_TYPE_USB3_UP);
 		if (!parent_up || !tb_port_is_enabled(parent_up))
 			return 0;
+
+		/* Make all unused bandwidth available for the new tunnel */
+		ret = tb_release_unused_usb3_bandwidth(tb, down, up);
+		if (ret)
+			return ret;
 	}
 
-	tunnel = tb_tunnel_alloc_usb3(tb, up, down);
-	if (!tunnel)
-		return -ENOMEM;
+	ret = tb_available_bandwidth(tb, down, up, &available_up,
+				     &available_down);
+	if (ret)
+		goto err_reclaim;
+
+	tb_port_dbg(up, "available bandwidth for new USB3 tunnel %d/%d Mb/s\n",
+		    available_up, available_down);
+
+	tunnel = tb_tunnel_alloc_usb3(tb, up, down, available_up,
+				      available_down);
+	if (!tunnel) {
+		ret = -ENOMEM;
+		goto err_reclaim;
+	}
 
 	if (tb_tunnel_activate(tunnel)) {
 		tb_port_info(up,
 			     "USB3 tunnel activation failed, aborting\n");
-		tb_tunnel_free(tunnel);
-		return -EIO;
+		ret = -EIO;
+		goto err_free;
 	}
 
 	list_add_tail(&tunnel->list, &tcm->tunnel_list);
+	if (tb_route(parent))
+		tb_reclaim_usb3_bandwidth(tb, down, up);
+
 	return 0;
+
+err_free:
+	tb_tunnel_free(tunnel);
+err_reclaim:
+	if (tb_route(parent))
+		tb_reclaim_usb3_bandwidth(tb, down, up);
+
+	return ret;
 }
 
 static int tb_create_usb3_tunnels(struct tb_switch *sw)
@@ -403,40 +608,40 @@ static void tb_scan_port(struct tb_port *port)
 	tb_scan_switch(sw);
 }
 
-static struct tb_tunnel *tb_find_tunnel(struct tb *tb, enum tb_tunnel_type type,
-					struct tb_port *src_port,
-					struct tb_port *dst_port)
-{
-	struct tb_cm *tcm = tb_priv(tb);
-	struct tb_tunnel *tunnel;
-
-	list_for_each_entry(tunnel, &tcm->tunnel_list, list) {
-		if (tunnel->type == type &&
-		    ((src_port && src_port == tunnel->src_port) ||
-		     (dst_port && dst_port == tunnel->dst_port))) {
-			return tunnel;
-		}
-	}
-
-	return NULL;
-}
-
 static void tb_deactivate_and_free_tunnel(struct tb_tunnel *tunnel)
 {
+	struct tb_port *src_port, *dst_port;
+	struct tb *tb;
+
 	if (!tunnel)
 		return;
 
 	tb_tunnel_deactivate(tunnel);
 	list_del(&tunnel->list);
 
-	/*
-	 * In case of DP tunnel make sure the DP IN resource is deallocated
-	 * properly.
-	 */
-	if (tb_tunnel_is_dp(tunnel)) {
-		struct tb_port *in = tunnel->src_port;
+	tb = tunnel->tb;
+	src_port = tunnel->src_port;
+	dst_port = tunnel->dst_port;
+
+	switch (tunnel->type) {
+	case TB_TUNNEL_DP:
+		/*
+		 * In case of DP tunnel make sure the DP IN resource is
+		 * deallocated properly.
+		 */
+		tb_switch_dealloc_dp_resource(src_port->sw, src_port);
+		fallthrough;
 
-		tb_switch_dealloc_dp_resource(in->sw, in);
+	case TB_TUNNEL_USB3:
+		tb_reclaim_usb3_bandwidth(tb, src_port, dst_port);
+		break;
+
+	default:
+		/*
+		 * PCIe and DMA tunnels do not consume guaranteed
+		 * bandwidth.
+		 */
+		break;
 	}
 
 	tb_tunnel_free(tunnel);
@@ -530,46 +735,6 @@ out:
 	return tb_find_unused_port(sw, TB_TYPE_PCIE_DOWN);
 }
 
-static int tb_available_bw(struct tb_cm *tcm, struct tb_port *in,
-			   struct tb_port *out)
-{
-	struct tb_switch *sw = out->sw;
-	struct tb_tunnel *tunnel;
-	int ret, bw, available_bw = 40000;
-
-	while (sw && sw != in->sw) {
-		bw = sw->link_speed * sw->link_width * 1000; /* Mb/s */
-		/* Leave 10% guard band */
-		bw -= bw / 10;
-
-		/*
-		 * Check for any active DP tunnels that go through this
-		 * switch and reduce their consumed bandwidth from
-		 * available.
-		 */
-		list_for_each_entry(tunnel, &tcm->tunnel_list, list) {
-			int consumed_bw;
-
-			if (!tb_tunnel_switch_on_path(tunnel, sw))
-				continue;
-
-			ret = tb_tunnel_consumed_bandwidth(tunnel, NULL,
-							   &consumed_bw);
-			if (ret)
-				return ret;
-
-			bw -= consumed_bw;
-		}
-
-		if (bw < available_bw)
-			available_bw = bw;
-
-		sw = tb_switch_parent(sw);
-	}
-
-	return available_bw;
-}
-
 static struct tb_port *tb_find_dp_out(struct tb *tb, struct tb_port *in)
 {
 	struct tb_port *host_port, *port;
@@ -609,10 +774,10 @@ static struct tb_port *tb_find_dp_out(struct tb *tb, struct tb_port *in)
 
 static void tb_tunnel_dp(struct tb *tb)
 {
+	int available_up, available_down, ret;
 	struct tb_cm *tcm = tb_priv(tb);
 	struct tb_port *port, *in, *out;
 	struct tb_tunnel *tunnel;
-	int available_bw;
 
 	/*
 	 * Find pair of inactive DP IN and DP OUT adapters and then
@@ -654,32 +819,41 @@ static void tb_tunnel_dp(struct tb *tb)
 		return;
 	}
 
-	/* Calculate available bandwidth between in and out */
-	available_bw = tb_available_bw(tcm, in, out);
-	if (available_bw < 0) {
-		tb_warn(tb, "failed to determine available bandwidth\n");
-		return;
+	/* Make all unused USB3 bandwidth available for the new DP tunnel */
+	ret = tb_release_unused_usb3_bandwidth(tb, in, out);
+	if (ret) {
+		tb_warn(tb, "failed to release unused bandwidth\n");
+		goto err_dealloc_dp;
 	}
 
-	tb_dbg(tb, "available bandwidth for new DP tunnel %u Mb/s\n",
-	       available_bw);
+	ret = tb_available_bandwidth(tb, in, out, &available_up,
+				     &available_down);
+	if (ret)
+		goto err_reclaim;
+
+	tb_dbg(tb, "available bandwidth for new DP tunnel %u/%u Mb/s\n",
+	       available_up, available_down);
 
-	tunnel = tb_tunnel_alloc_dp(tb, in, out, available_bw);
+	tunnel = tb_tunnel_alloc_dp(tb, in, out, available_up, available_down);
 	if (!tunnel) {
 		tb_port_dbg(out, "could not allocate DP tunnel\n");
-		goto dealloc_dp;
+		goto err_reclaim;
 	}
 
 	if (tb_tunnel_activate(tunnel)) {
 		tb_port_info(out, "DP tunnel activation failed, aborting\n");
-		tb_tunnel_free(tunnel);
-		goto dealloc_dp;
+		goto err_free;
 	}
 
 	list_add_tail(&tunnel->list, &tcm->tunnel_list);
+	tb_reclaim_usb3_bandwidth(tb, in, out);
 	return;
 
-dealloc_dp:
+err_free:
+	tb_tunnel_free(tunnel);
+err_reclaim:
+	tb_reclaim_usb3_bandwidth(tb, in, out);
+err_dealloc_dp:
 	tb_switch_dealloc_dp_resource(in->sw, in);
 }