On Mon, 20 Aug 2018, Arnd Bergmann wrote:
> On Mon, Aug 20, 2018 at 4:17 PM Mikulas Patocka <mpato...@redhat.com> wrote:
> > On Sun, 19 Aug 2018, ok...@codeaurora.org wrote:
> >
> > > +my new email
> > >
> > > On 2018-08-18 19:03, Arnd Bergmann wrote:
> > > > On Sat, Aug 18, 2018 at 12:05 AM Maciej W. Rozycki
> > > > <ma...@linux-mips.org>
>
> > > I think we need to identify the driver that is failing.
> >
> > It also may be some timing issue.
> >
> > I observed that not every kernel with the patch
> > 92d7223a74235054f2aa7227d207d9c57f84dca0 fails, some of them get stuck
> > only at boot, some get stuck only at shutdown, some not at all. Although
> > all the kernels with this patch reverted work.
> >
> > So the patch may have uncovered some timing problem somewhere.
> >
> > x86 has the function io_delay that injects delays between I/O accesses for
> > hardware that needs it - does alpha have something like this?
>
> The I/O delay would be very low on my list of possible root causes
> for this, hardly any hardware at all relies on it, and all uses I see
> are related to outb(), which you've already shown not to be the problem
> with my test patch.
>
> Arnd
The lockup happens somewhere in the function autoconfig in
drivers/tty/serial/8250/8250_port.c, but I don't know where exactly
because serial console doesn't work while the port is being probed.
When I use console on a graphics card, the lockup doesn't happen.
Mikulas
