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, 161 insertions, 0 deletions

diff --git a/drivers/thunderbolt/lc.c b/drivers/thunderbolt/lc.c
index df56523eb822..bd44d50246d2 100644
--- a/drivers/thunderbolt/lc.c
+++ b/drivers/thunderbolt/lc.c
@@ -205,3 +205,164 @@ bool tb_lc_lane_bonding_possible(struct tb_switch *sw)
 
 	return !!(val & TB_LC_PORT_ATTR_BE);
 }
+
+static int tb_lc_dp_sink_from_port(const struct tb_switch *sw,
+				   struct tb_port *in)
+{
+	struct tb_port *port;
+
+	/* The first DP IN port is sink 0 and second is sink 1 */
+	tb_switch_for_each_port(sw, port) {
+		if (tb_port_is_dpin(port))
+			return in != port;
+	}
+
+	return -EINVAL;
+}
+
+static int tb_lc_dp_sink_available(struct tb_switch *sw, int sink)
+{
+	u32 val, alloc;
+	int ret;
+
+	ret = tb_sw_read(sw, &val, TB_CFG_SWITCH,
+			 sw->cap_lc + TB_LC_SNK_ALLOCATION, 1);
+	if (ret)
+		return ret;
+
+	/*
+	 * Sink is available for CM/SW to use if the allocation valie is
+	 * either 0 or 1.
+	 */
+	if (!sink) {
+		alloc = val & TB_LC_SNK_ALLOCATION_SNK0_MASK;
+		if (!alloc || alloc == TB_LC_SNK_ALLOCATION_SNK0_CM)
+			return 0;
+	} else {
+		alloc = (val & TB_LC_SNK_ALLOCATION_SNK1_MASK) >>
+			TB_LC_SNK_ALLOCATION_SNK1_SHIFT;
+		if (!alloc || alloc == TB_LC_SNK_ALLOCATION_SNK1_CM)
+			return 0;
+	}
+
+	return -EBUSY;
+}
+
+/**
+ * tb_lc_dp_sink_query() - Is DP sink available for DP IN port
+ * @sw: Switch whose DP sink is queried
+ * @in: DP IN port to check
+ *
+ * Queries through LC SNK_ALLOCATION registers whether DP sink is available
+ * for the given DP IN port or not.
+ */
+bool tb_lc_dp_sink_query(struct tb_switch *sw, struct tb_port *in)
+{
+	int sink;
+
+	/*
+	 * For older generations sink is always available as there is no
+	 * allocation mechanism.
+	 */
+	if (sw->generation < 3)
+		return true;
+
+	sink = tb_lc_dp_sink_from_port(sw, in);
+	if (sink < 0)
+		return false;
+
+	return !tb_lc_dp_sink_available(sw, sink);
+}
+
+/**
+ * tb_lc_dp_sink_alloc() - Allocate DP sink
+ * @sw: Switch whose DP sink is allocated
+ * @in: DP IN port the DP sink is allocated for
+ *
+ * Allocate DP sink for @in via LC SNK_ALLOCATION registers. If the
+ * resource is available and allocation is successful returns %0. In all
+ * other cases returs negative errno. In particular %-EBUSY is returned if
+ * the resource was not available.
+ */
+int tb_lc_dp_sink_alloc(struct tb_switch *sw, struct tb_port *in)
+{
+	int ret, sink;
+	u32 val;
+
+	if (sw->generation < 3)
+		return 0;
+
+	sink = tb_lc_dp_sink_from_port(sw, in);
+	if (sink < 0)
+		return sink;
+
+	ret = tb_lc_dp_sink_available(sw, sink);
+	if (ret)
+		return ret;
+
+	ret = tb_sw_read(sw, &val, TB_CFG_SWITCH,
+			 sw->cap_lc + TB_LC_SNK_ALLOCATION, 1);
+	if (ret)
+		return ret;
+
+	if (!sink) {
+		val &= ~TB_LC_SNK_ALLOCATION_SNK0_MASK;
+		val |= TB_LC_SNK_ALLOCATION_SNK0_CM;
+	} else {
+		val &= ~TB_LC_SNK_ALLOCATION_SNK1_MASK;
+		val |= TB_LC_SNK_ALLOCATION_SNK1_CM <<
+			TB_LC_SNK_ALLOCATION_SNK1_SHIFT;
+	}
+
+	ret = tb_sw_write(sw, &val, TB_CFG_SWITCH,
+			  sw->cap_lc + TB_LC_SNK_ALLOCATION, 1);
+
+	if (ret)
+		return ret;
+
+	tb_port_dbg(in, "sink %d allocated\n", sink);
+	return 0;
+}
+
+/**
+ * tb_lc_dp_sink_dealloc() - De-allocate DP sink
+ * @sw: Switch whose DP sink is de-allocated
+ * @in: DP IN port whose DP sink is de-allocated
+ *
+ * De-allocate DP sink from @in using LC SNK_ALLOCATION registers.
+ */
+int tb_lc_dp_sink_dealloc(struct tb_switch *sw, struct tb_port *in)
+{
+	int ret, sink;
+	u32 val;
+
+	if (sw->generation < 3)
+		return 0;
+
+	sink = tb_lc_dp_sink_from_port(sw, in);
+	if (sink < 0)
+		return sink;
+
+	/* Needs to be owned by CM/SW */
+	ret = tb_lc_dp_sink_available(sw, sink);
+	if (ret)
+		return ret;
+
+	ret = tb_sw_read(sw, &val, TB_CFG_SWITCH,
+			 sw->cap_lc + TB_LC_SNK_ALLOCATION, 1);
+	if (ret)
+		return ret;
+
+	if (!sink)
+		val &= ~TB_LC_SNK_ALLOCATION_SNK0_MASK;
+	else
+		val &= ~TB_LC_SNK_ALLOCATION_SNK1_MASK;
+
+	ret = tb_sw_write(sw, &val, TB_CFG_SWITCH,
+			  sw->cap_lc + TB_LC_SNK_ALLOCATION, 1);
+	if (ret)
+		return ret;
+
+	tb_port_dbg(in, "sink %d de-allocated\n", sink);
+	return 0;
+}