thunderbolt: Assign remote for both ports in case of dual link

Currently the driver only assigns remote port for the primary port if in
case of dual link. This makes things such as walking from one port to
another more complex than necessary because the code needs to change
from secondary to primary port if the path that is established is
created using secondary links.

In order to always assign both remote pointers we need to prevent the
scanning code from following the secondary link. Failing to do that
might cause problems as the same switch may be enumerated twice (or
removed in case of unplug). Handle that properly by introducing a new
function tb_port_has_remote() that returns true only for the primary
port. We also update tb_is_upstream_port() to support both dual link
ports, make it take const port pointer and move it below
tb_upstream_port() to keep similar functions close.

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

drivers/thunderbolt/switch.c

@@ -1580,14 +1580,13 @@ void tb_switch_remove(struct tb_switch *sw)
 
 	/* port 0 is the switch itself and never has a remote */
 	for (i = 1; i <= sw->config.max_port_number; i++) {
-		if (tb_is_upstream_port(&sw->ports[i]))
-			continue;
-		if (sw->ports[i].remote)
+		if (tb_port_has_remote(&sw->ports[i])) {
 			tb_switch_remove(sw->ports[i].remote->sw);
-		sw->ports[i].remote = NULL;
-		if (sw->ports[i].xdomain)
+			sw->ports[i].remote = NULL;
+		} else if (sw->ports[i].xdomain) {
 			tb_xdomain_remove(sw->ports[i].xdomain);
-		sw->ports[i].xdomain = NULL;
+			sw->ports[i].xdomain = NULL;
+		}
 	}
 
 	if (!sw->is_unplugged)
@@ -1617,7 +1616,7 @@ void tb_sw_set_unplugged(struct tb_switch *sw)
 	}
 	sw->is_unplugged = true;
 	for (i = 0; i <= sw->config.max_port_number; i++) {
-		if (!tb_is_upstream_port(&sw->ports[i]) && sw->ports[i].remote)
+		if (tb_port_has_remote(&sw->ports[i]))
 			tb_sw_set_unplugged(sw->ports[i].remote->sw);
 	}
 }
@@ -1663,10 +1662,10 @@ int tb_switch_resume(struct tb_switch *sw)
 	/* check for surviving downstream switches */
 	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->remote)
+
+		if (!tb_port_has_remote(port))
 			continue;
+
 		if (tb_wait_for_port(port, true) <= 0
 			|| tb_switch_resume(port->remote->sw)) {
 			tb_port_warn(port,
@@ -1685,7 +1684,7 @@ void tb_switch_suspend(struct tb_switch *sw)
 		return;
 
 	for (i = 1; i <= sw->config.max_port_number; i++) {
-		if (!tb_is_upstream_port(&sw->ports[i]) && sw->ports[i].remote)
+		if (tb_port_has_remote(&sw->ports[i]))
 			tb_switch_suspend(sw->ports[i].remote->sw);
 	}