thunderbolt: Add support for lane bonding

Lane bonding allows aggregating two 10/20 Gb/s (depending on the
generation) lanes into a single 20/40 Gb/s bonded link. This allows
sharing the full bandwidth more efficiently. In order to establish lane
bonding we need to check that lane bonding is possible through link
controller and that both ends of the link actually supports 2x widths.
This also means that all the paths should be established through the
primary port so update tb_path_alloc() to handle this as well.

Lane bonding is supported starting from Falcon Ridge (2nd generation)
controllers.

We also expose the current speed and number of lanes under each device
except the host router following similar attribute naming than USB bus.
Expose speed and number of lanes for both directions to allow possibility
of asymmetric link in the future.

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

1 files changed, 18 insertions, 1 deletions

diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
index 382331d71c28..3353396e0806 100644
--- a/drivers/thunderbolt/tunnel.c
+++ b/drivers/thunderbolt/tunnel.c
@@ -90,6 +90,22 @@ static int tb_pci_activate(struct tb_tunnel *tunnel, bool activate)
 	return 0;
 }
 
+static int tb_initial_credits(const struct tb_switch *sw)
+{
+	/* If the path is complete sw is not NULL */
+	if (sw) {
+		/* More credits for faster link */
+		switch (sw->link_speed * sw->link_width) {
+		case 40:
+			return 32;
+		case 20:
+			return 24;
+		}
+	}
+
+	return 16;
+}
+
 static void tb_pci_init_path(struct tb_path *path)
 {
 	path->egress_fc_enable = TB_PATH_SOURCE | TB_PATH_INTERNAL;
@@ -101,7 +117,8 @@ static void tb_pci_init_path(struct tb_path *path)
 	path->drop_packages = 0;
 	path->nfc_credits = 0;
 	path->hops[0].initial_credits = 7;
-	path->hops[1].initial_credits = 16;
+	path->hops[1].initial_credits =
+		tb_initial_credits(path->hops[1].in_port->sw);
 }
 
 /**