thunderbolt: Add Display Port adapter pairing and resource management

To perform proper Display Port tunneling for Thunderbolt 3 devices we
need to allocate DP resources for DP IN port before they can be used.
The reason for this is that the user can also connect a monitor directly
to the Type-C ports in which case the Thunderbolt controller acts as
re-driver for Display Port (no tunneling takes place) taking the DP
sinks away from the connection manager. This allocation is done using
special sink allocation registers available through the link controller.

We can pair DP IN to DP OUT only if

 * DP IN has sink allocated via link controller
 * DP OUT port receives hotplug event

For DP IN adapters (only for the host router) we first query whether
there is DP resource available (it may be the previous instance of the
driver for example already allocated it) and if it is we add it to the
list. We then update the list when after each plug/unplug event to a DP
IN/OUT adapter. Each time the list is updated we try to find additional
DP IN <-> DP OUT pairs for tunnel establishment. This strategy also
makes it possible to establish another tunnel in case there are 3
monitors connected and one gets unplugged releasing the DP IN adapter
for the new tunnel.

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

1 files changed, 44 insertions, 0 deletions

diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index 205045caabdc..3f477df2730a 100644
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -645,6 +645,7 @@ static int tb_init_port(struct tb_port *port)
 		ida_init(&port->out_hopids);
 	}
 
+	INIT_LIST_HEAD(&port->list);
 	return 0;
 
 }
@@ -2333,6 +2334,49 @@ void tb_switch_suspend(struct tb_switch *sw)
 	tb_lc_set_sleep(sw);
 }
 
+/**
+ * tb_switch_query_dp_resource() - Query availability of DP resource
+ * @sw: Switch whose DP resource is queried
+ * @in: DP IN port
+ *
+ * Queries availability of DP resource for DP tunneling using switch
+ * specific means. Returns %true if resource is available.
+ */
+bool tb_switch_query_dp_resource(struct tb_switch *sw, struct tb_port *in)
+{
+	return tb_lc_dp_sink_query(sw, in);
+}
+
+/**
+ * tb_switch_alloc_dp_resource() - Allocate available DP resource
+ * @sw: Switch whose DP resource is allocated
+ * @in: DP IN port
+ *
+ * Allocates DP resource for DP tunneling. The resource must be
+ * available for this to succeed (see tb_switch_query_dp_resource()).
+ * Returns %0 in success and negative errno otherwise.
+ */
+int tb_switch_alloc_dp_resource(struct tb_switch *sw, struct tb_port *in)
+{
+	return tb_lc_dp_sink_alloc(sw, in);
+}
+
+/**
+ * tb_switch_dealloc_dp_resource() - De-allocate DP resource
+ * @sw: Switch whose DP resource is de-allocated
+ * @in: DP IN port
+ *
+ * De-allocates DP resource that was previously allocated for DP
+ * tunneling.
+ */
+void tb_switch_dealloc_dp_resource(struct tb_switch *sw, struct tb_port *in)
+{
+	if (tb_lc_dp_sink_dealloc(sw, in)) {
+		tb_sw_warn(sw, "failed to de-allocate DP resource for port %d\n",
+			   in->port);
+	}
+}
+
 struct tb_sw_lookup {
 	struct tb *tb;
 	u8 link;