thunderbolt: Add support for XDomain lane bonding

The USB4 Inter-Domain Service specification defines a protocol that can
be used to establish lane bonding between two USB4 domains (hosts). So
far we have not implemented it because the host controller DMA was not
fast enough to be able to go over 20 Gbits/s even if lanes were bonded.
However, starting from Intel Alder Lake CPUs the DMA can go over
20 Gbits/s so now it makes more sense to add this support to the driver.

Because both ends need to negotiate the bonding we add a simple state
machine that tracks the connection state and does the necessary steps
described by the USB4 Inter-Domain Service specification. We only
establish lane bonding when both sides of the link support it. Otherwise
we default to use the single lane. Also this is only done when software
connection manager is used. On systems with firmware based connection
manager, it handles the high-speed tunneling so bonding lanes is
specific to the implementation (Intel firmware based connection manager
does not support lane bonding).

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

1 files changed, 10 insertions, 9 deletions

diff --git a/include/linux/thunderbolt.h b/include/linux/thunderbolt.h
index 124e13cb1469..e13fe15e6a51 100644
--- a/include/linux/thunderbolt.h
+++ b/include/linux/thunderbolt.h
@@ -198,15 +198,15 @@ void tb_unregister_property_dir(const char *key, struct tb_property_dir *dir);
  * @local_property_block_len: Length of the @local_property_block in dwords
  * @remote_properties: Properties exported by the remote domain
  * @remote_property_block_gen: Generation of @remote_properties
- * @get_uuid_work: Work used to retrieve @remote_uuid
- * @uuid_retries: Number of times left @remote_uuid is requested before
- *		  giving up
- * @get_properties_work: Work used to get remote domain properties
- * @properties_retries: Number of times left to read properties
+ * @state: Next XDomain discovery state to run
+ * @state_work: Work used to run the next state
+ * @state_retries: Number of retries remain for the state
  * @properties_changed_work: Work used to notify the remote domain that
  *			     our properties have changed
  * @properties_changed_retries: Number of times left to send properties
  *				changed notification
+ * @bonding_possible: True if lane bonding is possible on local side
+ * @target_link_width: Target link width from the remote host
  * @link: Root switch link the remote domain is connected (ICM only)
  * @depth: Depth in the chain the remote domain is connected (ICM only)
  *
@@ -244,12 +244,13 @@ struct tb_xdomain {
 	u32 local_property_block_len;
 	struct tb_property_dir *remote_properties;
 	u32 remote_property_block_gen;
-	struct delayed_work get_uuid_work;
-	int uuid_retries;
-	struct delayed_work get_properties_work;
-	int properties_retries;
+	int state;
+	struct delayed_work state_work;
+	int state_retries;
 	struct delayed_work properties_changed_work;
 	int properties_changed_retries;
+	bool bonding_possible;
+	u8 target_link_width;
 	u8 link;
 	u8 depth;
 };