[PATCH AUTOSEL 6.18-6.1] thunderbolt: Don't create multiple DMA tunnels on firmware connection manager

[Sasha Levin]

From: Alan Borzeszkowski <alan.borzeszkowski@xxxxxxxxxxxxxxx>

[ Upstream commit cf0c38ee554c3e9062408cc3a38325483d52ecd0 ]

Firmware connection manager supports only one DMA tunnel per XDomain
connection. Firmware prior Intel Titan Ridge failed the operation
directly but the same does not happen anymore on Titan Ridge and
forward. For this reason add an explicit check, and fail the operation
accordingly in the driver.

Signed-off-by: Alan Borzeszkowski <alan.borzeszkowski@xxxxxxxxxxxxxxx>
Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---

LLM Generated explanations, may be completely bogus:

Background task results:

1. **`git log --all -S` (failed)** — The search with `--all` hung and
   produced no output; it was killed.

2. **`git log -S` without `--all` (succeeded)** — Completed in ~52s. In
   this 6.18.y tree, `icm_fr_approve_xdomain_paths` shows up at the
   `Linux 6.18-rc7` import (`ac3fd01e4c1ef`) and the bulk history point
   `19eef1d98eeda`. That confirms the ICM XDomain approve path is
   present in this tree; it doesn’t give a clean “introduced in mainline
   at commit X” answer because of how this checkout’s history is
   structured.

3. **Kernel.org subject search (succeeded, empty)** — A grep on
   torvalds/linux.git for the commit subject returned only the cgit page
   shell with no matching commits, so the patch wasn’t in mainline
   master at search time (or hadn’t landed yet).

None of this changes the earlier **YES** verdict: the buggy ICM path
exists in 6.18.43, the fix isn’t present, and the change is still
appropriate for stable.

 drivers/thunderbolt/icm.c     | 10 ++++++++++
 drivers/thunderbolt/xdomain.c | 25 +++++++++++++++++++------
 include/linux/thunderbolt.h   |  2 ++
 3 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/drivers/thunderbolt/icm.c b/drivers/thunderbolt/icm.c
index f213d9174dc57..961d66c2f81db 100644
--- a/drivers/thunderbolt/icm.c
+++ b/drivers/thunderbolt/icm.c
@@ -587,6 +587,11 @@ static int icm_fr_approve_xdomain_paths(struct tb *tb, struct tb_xdomain *xd,
 	struct icm_fr_pkg_approve_xdomain request;
 	int ret;
 
+	if (atomic_read(&xd->ntunnels) >= 1) {
+		tb_warn(tb, "only one tunnel is supported by the firmware\n");
+		return -EOPNOTSUPP;
+	}
+
 	memset(&request, 0, sizeof(request));
 	request.hdr.code = ICM_APPROVE_XDOMAIN;
 	request.link_info = xd->depth << ICM_LINK_INFO_DEPTH_SHIFT | xd->link;
@@ -1157,6 +1162,11 @@ static int icm_tr_approve_xdomain_paths(struct tb *tb, struct tb_xdomain *xd,
 	struct icm_tr_pkg_approve_xdomain request;
 	int ret;
 
+	if (atomic_read(&xd->ntunnels) >= 1) {
+		tb_warn(tb, "only one tunnel is supported by the firmware\n");
+		return -EOPNOTSUPP;
+	}
+
 	memset(&request, 0, sizeof(request));
 	request.hdr.code = ICM_APPROVE_XDOMAIN;
 	request.route_hi = upper_32_bits(xd->route);
diff --git a/drivers/thunderbolt/xdomain.c b/drivers/thunderbolt/xdomain.c
index 1eb149445fa05..e2c46366c8160 100644
--- a/drivers/thunderbolt/xdomain.c
+++ b/drivers/thunderbolt/xdomain.c
@@ -2021,6 +2021,7 @@ struct tb_xdomain *tb_xdomain_alloc(struct tb *tb, struct device *parent,
 	INIT_DELAYED_WORK(&xd->state_work, tb_xdomain_state_work);
 	INIT_DELAYED_WORK(&xd->properties_changed_work,
 			  tb_xdomain_properties_changed);
+	atomic_set(&xd->ntunnels, 0);
 
 	xd->local_uuid = kmemdup(local_uuid, sizeof(uuid_t), GFP_KERNEL);
 	if (!xd->local_uuid)
@@ -2302,9 +2303,15 @@ int tb_xdomain_enable_paths(struct tb_xdomain *xd, int transmit_path,
 			    int transmit_ring, int receive_path,
 			    int receive_ring)
 {
-	return tb_domain_approve_xdomain_paths(xd->tb, xd, transmit_path,
-					       transmit_ring, receive_path,
-					       receive_ring);
+	int ret;
+
+	ret = tb_domain_approve_xdomain_paths(xd->tb, xd, transmit_path,
+					      transmit_ring, receive_path,
+					      receive_ring);
+	if (ret)
+		return ret;
+	atomic_inc(&xd->ntunnels);
+	return 0;
 }
 EXPORT_SYMBOL_GPL(tb_xdomain_enable_paths);
 
@@ -2327,9 +2334,15 @@ int tb_xdomain_disable_paths(struct tb_xdomain *xd, int transmit_path,
 			     int transmit_ring, int receive_path,
 			     int receive_ring)
 {
-	return tb_domain_disconnect_xdomain_paths(xd->tb, xd, transmit_path,
-						  transmit_ring, receive_path,
-						  receive_ring);
+	int ret;
+
+	ret = tb_domain_disconnect_xdomain_paths(xd->tb, xd, transmit_path,
+						 transmit_ring, receive_path,
+						 receive_ring);
+	if (ret)
+		return ret;
+	atomic_dec(&xd->ntunnels);
+	return 0;
 }
 EXPORT_SYMBOL_GPL(tb_xdomain_disable_paths);
 
diff --git a/include/linux/thunderbolt.h b/include/linux/thunderbolt.h
index 7204586c10c3e..466f315f0be7b 100644
--- a/include/linux/thunderbolt.h
+++ b/include/linux/thunderbolt.h
@@ -230,6 +230,7 @@ enum tb_link_width {
  *				changed notification
  * @bonding_possible: True if lane bonding is possible on local side
  * @target_link_width: Target link width from the remote host
+ * @ntunnels: Keeps track of how many tunnels go through this XDomain
  * @link: Root switch link the remote domain is connected (ICM only)
  * @depth: Depth in the chain the remote domain is connected (ICM only)
  *
@@ -276,6 +277,7 @@ struct tb_xdomain {
 	int properties_changed_retries;
 	bool bonding_possible;
 	u8 target_link_width;
+	atomic_t ntunnels;
 	u8 link;
 	u8 depth;
 };
-- 
2.53.0