thunderbolt: Increase runtime PM reference count on DP tunnel discovery

stable inclusion
from stable-5.10.26
commit 6c3c90058b95c70f9e001a1d82aaf53b50562a08
bugzilla: 51363

--------------------------------

commit c94732bd upstream.

If the driver is unbound and then bound back it goes over the topology
and figure out the existing tunnels. However, if it finds DP tunnel it
should make sure the domain does not runtime suspend as otherwise it
will tear down the DP tunnel unexpectedly.

Fixes: 6ac6faee ("thunderbolt: Add runtime PM for Software CM")
Cc: stable@vger.kernel.org
Signed-off-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: N  Weilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/thunderbolt/tb.c

@@ -138,6 +138,10 @@ static void tb_discover_tunnels(struct tb_switch *sw)
 				parent->boot = true;
 				parent = tb_switch_parent(parent);
 			}
+		} else if (tb_tunnel_is_dp(tunnel)) {
+			/* Keep the domain from powering down */
+			pm_runtime_get_sync(&tunnel->src_port->sw->dev);
+			pm_runtime_get_sync(&tunnel->dst_port->sw->dev);
 		}
 
 		list_add_tail(&tunnel->list, &tcm->tunnel_list);