thunderbolt: Add support for Time Management Unit

Time Management Unit (TMU) is included in each USB4 router. It is used
to synchronize time across the USB4 fabric. By default when USB4 router
is plugged to the domain, its TMU is turned off. This differs from
Thunderbolt (1, 2 and 3) devices whose TMU is by default configured to
bi-directional HiFi mode. Since time synchronization is needed for
proper Display Port tunneling this means we need to configure the TMU on
USB4 compliant devices.

The USB4 spec allows some flexibility on how the TMU can be configured.
This makes it possible to enable link power management states (CLx) in
certain topologies, where for example DP tunneling is not used. TMU can
also be re-configured dynamicaly depending on types of tunnels created
over the USB4 fabric.

In this patch we simply configure the TMU to be in bi-directional HiFi
mode. This way we can tunnel any kind of traffic without need to perform
complex steps to re-configure the domain dynamically. We can add more
fine-grained TMU configuration later on when we start enabling CLx
states.

Signed-off-by: Rajmohan Mani <rajmohan.mani@intel.com>
Co-developed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Link: https://lore.kernel.org/r/20191217123345.31850-8-mika.westerberg@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 28 insertions, 0 deletions

diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index 6b99dcd1790c..e446624dd3e7 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -158,6 +158,25 @@ static void tb_scan_xdomain(struct tb_port *port)
 	}
 }
 
+static int tb_enable_tmu(struct tb_switch *sw)
+{
+	int ret;
+
+	/* If it is already enabled in correct mode, don't touch it */
+	if (tb_switch_tmu_is_enabled(sw))
+		return 0;
+
+	ret = tb_switch_tmu_disable(sw);
+	if (ret)
+		return ret;
+
+	ret = tb_switch_tmu_post_time(sw);
+	if (ret)
+		return ret;
+
+	return tb_switch_tmu_enable(sw);
+}
+
 static void tb_scan_port(struct tb_port *port);
 
 /**
@@ -257,6 +276,9 @@ static void tb_scan_port(struct tb_port *port)
 	if (tb_switch_lane_bonding_enable(sw))
 		tb_sw_warn(sw, "failed to enable lane bonding\n");
 
+	if (tb_enable_tmu(sw))
+		tb_sw_warn(sw, "failed to enable TMU\n");
+
 	tb_scan_switch(sw);
 }
 
@@ -709,6 +731,7 @@ static void tb_handle_hotplug(struct work_struct *work)
 			tb_sw_set_unplugged(port->remote->sw);
 			tb_free_invalid_tunnels(tb);
 			tb_remove_dp_resources(port->remote->sw);
+			tb_switch_tmu_disable(port->remote->sw);
 			tb_switch_lane_bonding_disable(port->remote->sw);
 			tb_switch_remove(port->remote->sw);
 			port->remote = NULL;
@@ -855,6 +878,8 @@ static int tb_start(struct tb *tb)
 		return ret;
 	}
 
+	/* Enable TMU if it is off */
+	tb_switch_tmu_enable(tb->root_switch);
 	/* Full scan to discover devices added before the driver was loaded. */
 	tb_scan_switch(tb->root_switch);
 	/* Find out tunnels created by the boot firmware */
@@ -886,6 +911,9 @@ static void tb_restore_children(struct tb_switch *sw)
 {
 	struct tb_port *port;
 
+	if (tb_enable_tmu(sw))
+		tb_sw_warn(sw, "failed to restore TMU configuration\n");
+
 	tb_switch_for_each_port(sw, port) {
 		if (!tb_port_has_remote(port))
 			continue;