On Mon, Oct 09, 2017 at 10:45:39PM +0200, Mason wrote:
> On 09/10/2017 19:01, Bjorn Helgaas wrote:
> ...

> > In that thread, Mason reported a regression that looks similar, but as
> > far as I can tell, we never identified a root cause.
> > 
> >   1) The problem Mason reported was on a Tango platform, which has a
> >      known hardware issue that corrupts data when simultaneous config
> >      and MMIO accesses occur.  You're seeing the problem on a
> >      different platform, which is very helpful.
> 
> As mentioned here:
> https://www.mail-archive.com/linux-usb@vger.kernel.org/msg94020.html
> 
> When I disable the AER driver, not a single config space access
> occurs when a USB drive is unplugged. So I'm 99.99% sure that
> the issue is NOT caused by tango's bad design. (I got the vibe
> that nobody cared about tango's issue because it was assumed
> that the design flaw was responsible for it.)

I agree; I don't think this is Tango's fault.

Can you test fe190ed0d602 and d9f11ba9f107 to determine whether
d9f11ba9f107 is the culprit?  If it is the culprit, can you try reverting
it on a current kernel to see if that fixes it?

If d9f11ba9f107 is not the culprit, can you bisect to discover exactly
where it broke?

> >   2) Mathias suggested d9f11ba9f107 ("xhci: Rework how we handle
> >      unresponsive or hoptlug removed hosts"), which appeared in
> >      v4.12-rc1, as a possible culprit, but I don't see a bisection
> >      that definitively identifies this commit.
> > 
> >      Is it possible for you to test both fe190ed0d602 ("xhci: Do not
> >      halt the host until both HCD have disconnected their devices.")
> >      and d9f11ba9f107 ("xhci: Rework how we handle unresponsive or
> >      hoptlug removed hosts") so we can tell for sure whether
> >      d9f11ba9f107 broke it?
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