[PATCH 2/5] thunderbolt: Check that lane 1 is in CL0 before enabling lane bonding

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Marek reported that when BlackMagic UltraStudio device is connected the
kernel repeatedly tries to enable lane bonding without success making
the device non-functional. It looks like the device does not have lane 1
connected at all so even though it is enabled we should not try to bond
the lanes. For this reason check that lane 1 is in fact CL0 (connected,
active) before attempting to bond the lanes.

Reported-by: Marek Šanta <teslan223@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217737
Cc: stable@vger.kernel.org
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/thunderbolt/switch.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index 43171cc1cc2d..bd5815f8f23b 100644
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -2725,6 +2725,13 @@ int tb_switch_lane_bonding_enable(struct tb_switch *sw)
 	    !tb_port_is_width_supported(down, TB_LINK_WIDTH_DUAL))
 		return 0;
 
+	/*
+	 * Both lanes need to be in CL0. Here we assume lane 0 already be in
+	 * CL0 and check just for lane 1.
+	 */
+	if (tb_wait_for_port(down->dual_link_port, false) <= 0)
+		return -ENOTCONN;
+
 	ret = tb_port_lane_bonding_enable(up);
 	if (ret) {
 		tb_port_warn(up, "failed to enable lane bonding\n");
-- 
2.40.1