A Decade Later, Linux To Better Handle Daisy Chaining Thunderbolt Displays On Apple Hardware

Intel's Thunderbolt "Light Ridge" controller was introduced all the way back in 2010 for Apple Macs and the updated Intel Thunderbolt 2 "Falcon Ridge" controller is from 2013. Now in 2022 under Linux the Thunderbolt driver will be better matching the Apple macOS behavior when daisy chaining multiple Thunderbolt displays.

Up to now on Linux when daisy chaining multiple displays via Thunderbolt with these old controllers there has been the possibility of display tearing and flickering, depending upon the resolution and refresh rate. It turns out the Thunderbolt driver on Linux with old Thunderbolt 1 hardware has been tunneling the multiple displays through the same lane. In other words, sharing the same 10 Gb/s lane when there is a second potentially unused lane available.

In a Thunderbolt "next" change likely landing for Linux 5.19, rather than sharing that 10 Gb/s bandwidth the second tunnel will now go through the separate Thunderbolt lane. This is reported to match what is done by macOS and should avoid tearing/flickering with Thunderbolt displays on old Apple hardware. Newer Thunderbolt hardware with lane bonding shouldn't exhibit this issue.

Better late than never and that small change is now queued in Thunderbolt's "next" ahead of Linux 5.19.