thunderbolt: Fix Thunderbolt 3 display flickering issue on 2nd hot plug onwards

BugLink: https://bugs.launchpad.net/bugs/2034491
commit 583893a66d731f5da010a3fa38a0460e05f0149b upstream.

Previously, on unplug events, the TMU mode was disabled first
followed by the Time Synchronization Handshake, irrespective of
whether the tb_switch_tmu_rate_write() API was successful or not.

However, this caused a problem with Thunderbolt 3 (TBT3)
devices, as the TSPacketInterval bits were always enabled by default,
leading the host router to assume that the device router's TMU was
already enabled and preventing it from initiating the Time
Synchronization Handshake. As a result, TBT3 monitors experienced
display flickering from the second hot plug onwards.

To address this issue, we have modified the code to only disable the
Time Synchronization Handshake during TMU disable if the
tb_switch_tmu_rate_write() function is successful. This ensures that
the TBT3 devices function correctly and eliminates the display
flickering issue.

Co-developed-by: Sanath S <Sanath.S@amd.com>
Signed-off-by: Sanath S <Sanath.S@amd.com>
Signed-off-by: Sanjay R Mehta <sanju.mehta@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
[ USB4v2 introduced support for uni-directional TMU mode as part of
  d49b4f043d63 ("thunderbolt: Add support for enhanced uni-directional TMU mode")
  This is not a stable candidate commit, so adjust the code for backport. ]
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit f016326d31d010433b2a1a08a4856c214ae829eb linux-6.1.y)
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Roxana Nicolescu <roxana.nicolescu@canonical.com>
Signed-off-by: Roxana Nicolescu <roxana.nicolescu@canonical.com>

diff --git a/drivers/thunderbolt/tmu.c b/drivers/thunderbolt/tmu.c
index 626aca3124b1c1fea877fb15ca7147b2a6de5a42..d9544600b386778e7a7402b815be565753bde327 100644 (file)
--- a/drivers/thunderbolt/tmu.c
+++ b/drivers/thunderbolt/tmu.c
@@ -415,7 +415,8 @@ int tb_switch_tmu_disable(struct tb_switch *sw)
                 * uni-directional mode and we don't want to change it's TMU
                 * mode.
                 */
-               tb_switch_tmu_rate_write(sw, TB_SWITCH_TMU_RATE_OFF);
+               ret = tb_switch_tmu_rate_write(sw, TB_SWITCH_TMU_RATE_OFF);
+                       return ret;
 
                tb_port_tmu_time_sync_disable(up);
                ret = tb_port_tmu_time_sync_disable(down);