Re: Problem with USB2 devices connected to a hub

[Georg Chini <georg@xxxxxxxx>]

On 08.04.19 08:46, Georg Chini wrote:
> 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
Here are the traces. In the beginning, there is no USB device connected. 
Then I connect a hub
(this time a simple 4 port USB 2.0 hub). After that I connect an USB 
sound device to the hub.

Hope it helps.

Regards
            Georg

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