I tested again on kernels 5.8 and 5.11 with nvidia-driver-470. Logs are attached.
With 5.8 kernel, the external displays eventually come to live, after connecting the dock and some waiting (~15 s). After first connection, it seemed to be doing several trials, in the end it worked too. With 5.11 kernel, the external displays remain black, and computer was lagging or almost frozen. I'll see what I can do with 5.13 kernel. ** Attachment added: "Logs from 5.8 and 5.11 kernels with nvidia v470 driver" https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1938999/+attachment/5517301/+files/logs_2021-08-11.zip -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1938999 Title: External displays not working on Thinkpad T490 with ThinkPad Thunderbolt 3 Dock Status in linux package in Ubuntu: Confirmed Bug description: I have two external displays chained via Display port connected to the ThinkPad Thunderbolt 3 Dock. They are working with kernel 5.8.0-63 but not with the new 5.11.0-25 kernel. I could reproduce this behavior several times for both kernels, as follows: I booted up with disconnected dock, logged in, then I connected it, disconnected it, and connected it again. With the 5.11.0-25 kernel the external displays go black; the main screen turns off and on several times. Sometimes the main screen remains working, but UI is lagging. I'm attaching the logs. Two separate boots for each variant are marked 'a'/'b'. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1938999/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
