Re: Problem with USB2 devices connected to a hub

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On 02.04.19 16:52, Mathias Nyman wrote:
On 28.3.2019 15.41, Mathias Nyman wrote:

The issue happens when only a single hub and a single device is connected to the USB subsystem. On my previous board, I had two USB dongles and two sound devices connected to the same hub and it worked without issues. So I guess it is not a real bandwidth limit. Somehow the hub seems to eat the bandwidth.


Can/will you investigate this problem further or do I have to live with it? Or is there
anything more I can do?


This is one of the items I'm looking at.

xHC hw calculates bandwidth usage when endpoints are added based on values in endpoint context. The traces unfortunately didn't support this, so new tracing support was needed, added here to my
bandwith-debug branch:

git://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git bandwidth-debug

xHC hw can also report available bandwidth, but we don't yet have driver support. I was planning on adding a hack that checks the available bandwidth after every endpoint change
and add it to the testbranch, but that part is not yet finished.

New traces using the bandwidth-debug testbranch could be useful, even without the "available bandwidth"
support


available bandwidth tracking added to bandwidth-debug branch, any chance you could take new traces?

-Mathias

Sorry, only just read the mail, will do so in the next days.




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