thunderbolt: Keep the domain powered when USB4 port is in redrive mode

If a DiplayPort cable is directly connected to the host routers USB4
port, there is no tunnel involved but the port is in "redrive" mode
meaning that it is re-driving the DisplayPort signals from its
DisplayPort source. In this case we need to keep the domain powered on
otherwise once the domain enters D3cold the connected monitor blanks
too.

Since this happens only on Intel Barlow Ridge add a quirk that takes
runtime PM reference if we detect that the USB4 port entered redrive
mode (and release it once it exits the mode).

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

1 files changed, 48 insertions, 1 deletions

diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index 306c62c35a05..c5ce7a694b27 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -1973,6 +1973,49 @@ static void tb_tunnel_dp(struct tb *tb)
 		tb_dbg(tb, "no suitable DP IN adapter available, not tunneling\n");
 }
 
+static void tb_enter_redrive(struct tb_port *port)
+{
+	struct tb_switch *sw = port->sw;
+
+	if (!(sw->quirks & QUIRK_KEEP_POWER_IN_DP_REDRIVE))
+		return;
+
+	/*
+	 * If we get hot-unplug for the DP IN port of the host router
+	 * and the DP resource is not available anymore it means there
+	 * is a monitor connected directly to the Type-C port and we are
+	 * in "redrive" mode. For this to work we cannot enter RTD3 so
+	 * we bump up the runtime PM reference count here.
+	 */
+	if (!tb_port_is_dpin(port))
+		return;
+	if (tb_route(sw))
+		return;
+	if (!tb_switch_query_dp_resource(sw, port)) {
+		port->redrive = true;
+		pm_runtime_get(&sw->dev);
+		tb_port_dbg(port, "enter redrive mode, keeping powered\n");
+	}
+}
+
+static void tb_exit_redrive(struct tb_port *port)
+{
+	struct tb_switch *sw = port->sw;
+
+	if (!(sw->quirks & QUIRK_KEEP_POWER_IN_DP_REDRIVE))
+		return;
+
+	if (!tb_port_is_dpin(port))
+		return;
+	if (tb_route(sw))
+		return;
+	if (port->redrive && tb_switch_query_dp_resource(sw, port)) {
+		port->redrive = false;
+		pm_runtime_put(&sw->dev);
+		tb_port_dbg(port, "exit redrive mode\n");
+	}
+}
+
 static void tb_dp_resource_unavailable(struct tb *tb, struct tb_port *port)
 {
 	struct tb_port *in, *out;
@@ -1989,7 +2032,10 @@ static void tb_dp_resource_unavailable(struct tb *tb, struct tb_port *port)
 	}
 
 	tunnel = tb_find_tunnel(tb, TB_TUNNEL_DP, in, out);
-	tb_deactivate_and_free_tunnel(tunnel);
+	if (tunnel)
+		tb_deactivate_and_free_tunnel(tunnel);
+	else
+		tb_enter_redrive(port);
 	list_del_init(&port->list);
 
 	/*
@@ -2016,6 +2062,7 @@ static void tb_dp_resource_available(struct tb *tb, struct tb_port *port)
 	tb_port_dbg(port, "DP %s resource available after hotplug\n",
 		    tb_port_is_dpin(port) ? "IN" : "OUT");
 	list_add_tail(&port->list, &tcm->dp_resources);
+	tb_exit_redrive(port);
 
 	/* Look for suitable DP IN <-> DP OUT pairs now */
 	tb_tunnel_dp(tb);