Possible regression between 4.9 and 4.13

[Greg Kroah-Hartman]

On Wed, Aug 30, 2017 at 10:07:59AM +0100, Ard Biesheuvel wrote:
> On 30 August 2017 at 09:55, Mason <slash.tmp at free.fr> wrote:
> > On 30/08/2017 08:02, Greg Kroah-Hartman wrote:
> >
> >> To get back to the original issue here, the hardware seems to have died,
> >> the driver stops talking to it, and all is good.  The "regression" here
> >> is that we now properly can determine that the hardware is crap.
> >
> > Before 4.12, when I unplugged my USB3 Flash drive, Linux would
> > detect a few "Uncorrected Non-Fatal errors" via AER, but it was
> > still possible to plug the drive back in.
> >
> > Since 4.12, once I unplug the drive, the whole USB3 card is marked
> > as dead (all 4 ports), and I can no longer plug anything in (not even
> > the USB2 drive that didn't have any issues, IIRC).
> >
> > It seems a bit premature to "mark as dead" something that remains
> > functional, doesn't it?
> >
> > Disclaimer, there are many variables in this setup, and I've only
> > tested a small fraction of the problem space: only one system,
> > only one USB3 board, only one USB3 Flash drive.
> >
> 
> Please don't forget to mention that this is quirky hardware that
> depends on BROKEN because it multiplexes MMIO and config space
> accesses in the same memory window without any locking whatsoever
> (which would be difficult to do in the first place because we don't
> use accessors for MMIO in the kernel).
> 
> So how likely is it that you are attempting to read from the xhci BAR
> window while a config space access is in progress? Any way to
> instrument this in your driver?

Seriously?  Ok, that's crap hardware, sorry, I don't feel bad at all
here.  You are going to have worse problems than just a single USB
controller issue if that's your hardware design, go kick some hardware
engineers for me please.

good luck, you are on your own :(

greg k-h