thunderbolt: Introduce tb_port_path_direction_downstream()

Introduce tb_port_path_direction_downstream() to check if path from
source adapter to destination adapter is directed towards downstream.
Convert existing users to call this helper instead of open-coding.

No functional changes.
Signed-off-by: Gil Fine <gil.fine@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/tb.c

@@ -553,7 +553,7 @@ static struct tb_tunnel *tb_find_first_usb3_tunnel(struct tb *tb,
 	struct tb_switch *sw;
 
 	/* Pick the router that is deepest in the topology */
-	if (dst_port->sw->config.depth > src_port->sw->config.depth)
+	if (tb_port_path_direction_downstream(src_port, dst_port))
 		sw = dst_port->sw;
 	else
 		sw = src_port->sw;
@@ -1224,7 +1224,7 @@ tb_recalc_estimated_bandwidth_for_group(struct tb_bandwidth_group *group)
 			      "re-calculated estimated bandwidth %u/%u Mb/s\n",
 			      estimated_up, estimated_down);
 
-		if (in->sw->config.depth < out->sw->config.depth)
+		if (tb_port_path_direction_downstream(in, out))
 			estimated_bw = estimated_down;
 		else
 			estimated_bw = estimated_up;
@@ -1958,7 +1958,7 @@ static void tb_handle_dp_bandwidth_request(struct work_struct *work)
 
 	out = tunnel->dst_port;
 
-	if (in->sw->config.depth < out->sw->config.depth) {
+	if (tb_port_path_direction_downstream(in, out)) {
 		requested_up = -1;
 		requested_down = requested_bw;
 	} else {

drivers/thunderbolt/tb.h

@@ -1041,6 +1041,21 @@ void tb_port_release_out_hopid(struct tb_port *port, int hopid);
 struct tb_port *tb_next_port_on_path(struct tb_port *start, struct tb_port *end,
 				     struct tb_port *prev);
 
+/**
+ * tb_port_path_direction_downstream() - Checks if path directed downstream
+ * @src: Source adapter
+ * @dst: Destination adapter
+ *
+ * Returns %true only if the specified path from source adapter (@src)
+ * to destination adapter (@dst) is directed downstream.
+ */
+static inline bool
+tb_port_path_direction_downstream(const struct tb_port *src,
+				  const struct tb_port *dst)
+{
+	return src->sw->config.depth < dst->sw->config.depth;
+}
+
 static inline bool tb_port_use_credit_allocation(const struct tb_port *port)
 {
 	return tb_port_is_null(port) && port->sw->credit_allocation;

drivers/thunderbolt/tunnel.c

@@ -687,7 +687,7 @@ static int tb_dp_xchg_caps(struct tb_tunnel *tunnel)
 		      "DP OUT maximum supported bandwidth %u Mb/s x%u = %u Mb/s\n",
 		      out_rate, out_lanes, bw);
 
-	if (in->sw->config.depth < out->sw->config.depth)
+	if (tb_port_path_direction_downstream(in, out))
 		max_bw = tunnel->max_down;
 	else
 		max_bw = tunnel->max_up;
@@ -812,7 +812,7 @@ static int tb_dp_bandwidth_alloc_mode_enable(struct tb_tunnel *tunnel)
 	 * max_up/down fields. For discovery we just read what the
 	 * estimation was set to.
 	 */
-	if (in->sw->config.depth < out->sw->config.depth)
+	if (tb_port_path_direction_downstream(in, out))
 		estimated_bw = tunnel->max_down;
 	else
 		estimated_bw = tunnel->max_up;
@@ -982,7 +982,7 @@ static int tb_dp_bandwidth_mode_consumed_bandwidth(struct tb_tunnel *tunnel,
 	if (allocated_bw == max_bw)
 		allocated_bw = ret;
 
-	if (in->sw->config.depth < out->sw->config.depth) {
+	if (tb_port_path_direction_downstream(in, out)) {
 		*consumed_up = 0;
 		*consumed_down = allocated_bw;
 	} else {
@@ -1017,7 +1017,7 @@ static int tb_dp_allocated_bandwidth(struct tb_tunnel *tunnel, int *allocated_up
 		if (allocated_bw == max_bw)
 			allocated_bw = ret;
 
-		if (in->sw->config.depth < out->sw->config.depth) {
+		if (tb_port_path_direction_downstream(in, out)) {
 			*allocated_up = 0;
 			*allocated_down = allocated_bw;
 		} else {
@@ -1045,7 +1045,7 @@ static int tb_dp_alloc_bandwidth(struct tb_tunnel *tunnel, int *alloc_up,
 	if (ret < 0)
 		return ret;
 
-	if (in->sw->config.depth < out->sw->config.depth) {
+	if (tb_port_path_direction_downstream(in, out)) {
 		tmp = min(*alloc_down, max_bw);
 		ret = usb4_dp_port_allocate_bandwidth(in, tmp);
 		if (ret)
@@ -1143,7 +1143,7 @@ static int tb_dp_maximum_bandwidth(struct tb_tunnel *tunnel, int *max_up,
 	if (ret < 0)
 		return ret;
 
-	if (in->sw->config.depth < tunnel->dst_port->sw->config.depth) {
+	if (tb_port_path_direction_downstream(in, tunnel->dst_port)) {
 		*max_up = 0;
 		*max_down = ret;
 	} else {
@@ -1201,7 +1201,7 @@ static int tb_dp_consumed_bandwidth(struct tb_tunnel *tunnel, int *consumed_up,
 		return 0;
 	}
 
-	if (in->sw->config.depth < tunnel->dst_port->sw->config.depth) {
+	if (tb_port_path_direction_downstream(in, tunnel->dst_port)) {
 		*consumed_up = 0;
 		*consumed_down = tb_dp_bandwidth(rate, lanes);
 	} else {