From f016326d31d010433b2a1a08a4856c214ae829eb Mon Sep 17 00:00:00 2001 From: Sanjay R Mehta Date: Wed, 2 Aug 2023 06:11:49 -0500 Subject: [PATCH] thunderbolt: Fix Thunderbolt 3 display flickering issue on 2nd hot plug onwards 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 Signed-off-by: Sanath S Signed-off-by: Sanjay R Mehta Cc: stable@vger.kernel.org Signed-off-by: Mika Westerberg [ 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 Signed-off-by: Greg Kroah-Hartman --- drivers/thunderbolt/tmu.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/thunderbolt/tmu.c b/drivers/thunderbolt/tmu.c index 626aca3..d954460 100644 --- 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); -- 2.7.4