Re: [PATCH V2] thunderbolt: Fix Thunderbolt 3 display flickering issue on 2nd hot plug onwards

[Sanjay R Mehta <sanmehta@amd.com>]

On 7/31/2023 4:45 PM, Mika Westerberg wrote:
> On Wed, Jul 12, 2023 at 01:16:19PM -0500, Sanjay R Mehta wrote:
>> 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>
> 
> Looks good.
> 
> I suppose you want this in -stable too, right?

Thanks. Yes Mika.

- Sanjay