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Date:   Wed, 20 Feb 2019 10:29:20 +0100
From:   Johan Hovold <johan@kernel.org>
To:     Nix <nix@esperi.org.uk>
Cc:     Johan Hovold <johan@kernel.org>, Greg KH <greg@kroah.com>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: 4.20.7: pl2303 not working (post-4.19 regression) (limited info
 so far, not yet bisected)
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On Mon, Feb 18, 2019 at 10:32:57AM +0000, Nix wrote:
> On 18 Feb 2019, Johan Hovold stated:
> 
> > On Sun, Feb 17, 2019 at 07:13:52PM +0000, Nix wrote:
> >> I'm still fairly sure this is a regression -- my machines are often up
> >> for a lot longer than that and I've never seen this before I upgraded to
> >> 4.20.x -- but I don't think I'm going to identify it by mindless
> >> bisection. I might have to actually *think* about it.
> >
> > I doubt it's a regression in usb-serial as essentially nothing changed
> > with respect to pl2303 or core since 4.19.
> 
> Yeah, I came to that conclusion as well.
> 
> > The -ENOSPC you're seeing is returned by the host controller to
> > indicate:
> >
> > 	This request would overcommit the usb bandwidth reserved for
> > 	periodic transfers (interrupt, isochronous).
> 
> Side note: probably not related to *this* -ENOSPC, which I've been
> seeing for a few releases now and which appears to break Chromium's U2F
> negotiation when the USB bus has sufficiently weird devices on it (like,
> uh, my wireless mouse):
> 
> <https://bugs.chromium.org/p/chromium/issues/detail?id=932699>
> 
> (I say "probably not related" because it's much older and long predates
> the pl2303 trouble.)

Yeah, hard to tell from a quick look.

> > but if you're saying you can reproduce this on "every box" it may not be
> > related to any particular host-controller driver (or USB topology).
> 
> They are all xhci, at least. The pl2303 is USB 2. One machine, a
> two-year-old Broadwell server, says:

> So the quirks are all totally different, and the controllers are quite
> different as well...

Yeah, but they are all xhci as you point out so theoretically it could
be an xhci driver regression.

Johan