am335x: 5.18.x: system stalling

[Arnd Bergmann]

On Thu, May 26, 2022 at 2:37 PM Yegor Yefremov
<yegorslists at googlemail.com> wrote:
> On Thu, May 26, 2022 at 10:19 AM Ard Biesheuvel <ardb at kernel.org> wrote:
> >
> > On Thu, 26 May 2022 at 08:20, Tony Lindgren <tony at atomide.com> wrote:
> > >
> > > * Yegor Yefremov <yegorslists at googlemail.com> [220526 05:45]:
> > > > On Tue, May 24, 2022 at 4:19 PM Tony Lindgren <tony at atomide.com> wrote:
> > > > > Maybe also try with CONFIG_MUSB_PIO_ONLY=y to see if it makes things
> > > > > better or worse :)
> > > >
> > > > PIO is always the last resort :-) And now it proves it again. With
> > > > PIO_ONLY the system doesn't stall.
> > >
> > > OK great :) So it has something to do with drivers/dma/ti/cppi41.c, or
> > > with drivers/usb/musb/cppi_dma.c or whatever the dma for am335x here
> > > is. Or maybe there's something using stack for buffers being passed to
> > > dma again that breaks with vmap stack.
> > >
> >
> > In order to confirm this theory, could you please try rebuilding your
> > kernel with CONFIG_VMAP_STACK disabled, and leave everything else as
> > before?
>
> I have disabled the CONFIG_VMAP_STACK option:
>
> # zcat /proc/config.gz | grep VMAP_STACK
> CONFIG_HAVE_ARCH_VMAP_STACK=y
> # CONFIG_VMAP_STACK is not set
>
> The system stalls.

Ok, I guess that means we can stop looking for invalid DMA buffers
on stacks. Out of the original commits you listed as possible causes,
we can also rule out 23d9a9280efe ("ARM: 9177/1: disable vmap'ed
stacks on suspend-capable SMP configs") and cafc0eab1689
("ARM: v7m: enable support for IRQ stacks"). It could still be
9c46929e7989 ("ARM: implement THREAD_INFO_IN_TASK for
uniprocessor systems") and 5fe41793bc78 ("ARM: 9176/1: avoid
literal references in inline assembly") or possibly the merge.

Can you post the whole .config file somewhere for reference?
In particular, do you have CONFIG_SMP, CONFIG_LD_IS_LLD
or CURRENT_POINTER_IN_TPIDRURO set?

      Arnd