xHCI Driver Compliance Test Support

[Rob Weber <rob@gnarbox.com>]

Hi Mathias,

I am working on running our custom USB dual-role product through some
compliance testing. It seems that the SoC and host controller are
not responding to the LFPS signaling and timeout that is supposed to
automatically begin the compliance test sequence.

I'm currently running a 4.9.115 kernel, and I'm afraid I might be
missing some critical patches for compliance test support. I noticed
these two patches came up in a google search:

https://patchwork.kernel.org/patch/10415345/
https://www.spinics.net/lists/linux-usb/msg160002.html

Besides these patches, is there anything else that comes to mind that I
might need to do to start compliance testing? I'm about to build a more
recent kernel to see if that improves my situation as well.

Just for reference, our product uses an intel atom z8550 SoC that uses
an xHCI host controller and a dwc3 device controller. Our platform also
uses a USB 3.0 redriver. The datasheet for this redriver (tusb542)
indicates that it's internal LFPS controller supports full USB 3.0
compliance requirements.

Thanks in advance for your guidance!

Cheers,
Rob Weber