Re: [PATCH 6.4.y] thunderbolt: Fix Thunderbolt 3 display flickering issue on 2nd hot plug onwards

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Aug 23, 2023 at 02:18:25PM -0500, Mario Limonciello wrote:
> From: Sanjay R Mehta <sanju.mehta@amd.com>
> 
> 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>
> (cherry picked from commit 583893a66d731f5da010a3fa38a0460e05f0149b)
> 
> 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>

Both now applied, thanks.

greg k-h