Clear Linux & TB4/USB4

I have some equipment on order that will contain a USB-C type “USB4” port.

When this equipment arrives, as always I will be testing Clear Linux on it.

From my research “USB4” and “Thunderbolt 4” are functionally interchangeable with the only exception being with the use of Windows which may (or may not) throttle the bandwidth to 20Gbps.

I understand any functionality/compatibility will be at the foremost, kernel release based.

Your source library shows your GA at kernel 5.58. (October 2022)

The kernel reference shows USB4/TB4 support currently in 6.1rc5

Even though Clear has deprecated its priority around desktop functionality, I will be testing USB4 around certain use cases that are not typically in a desktop.

Intel has been typically up to speed (no pun intended) on Thunderbolt support, just curious what the thoughts are from the Clear Linux team on its use.

1 Like

I have installed Clear Linux (Build 37780) with kernel level 6.1.0-1221.native on a Minis Forum UM690 mini PC.

This new device has the front C port labeled “USB4” so I wanted to try some devices to see what kind of speeds were going to be allowed.

The first I tried was a HP USB-C Dock and it reported that the best interface was USB 3.2 Gen 2 off the front port.

Then I tried the Thunderbolt 3 version of the same dock. Clear Linux loaded the “thunderbolt” kernel module and the dock worked fine as all the interfaces showed up as working. (I did not do a complete test on the display outputs for this dock) The only issues was that the USB4 port could only report 10Gbps on TB3. The next line in the output showed the byte level, with the title “Unexpected”. I can only assume this was where the 40Gbps would have been displayed. The USB ports on the dock all showed 5 or 10Gbps available.

lspci shows that the USB4 controller has 16GT/s with x16 width. Under the PCI 4.0 spec that is 31.5Gbps before overhead.

Is any of this a Clear Linux problem? I don’t think so. The TB3 cable is .7m long. The correct kernel module loaded (thunderbolt). It makes me think that the USB4 controller is either immature or they are restricting the throughput for now.

There are many articles on just how murky the USB4 waters are and how confusing the TB support can be. But I wanted to give Clear Linux a first shot to see what happens.