am335x: 5.18.x: system stalling

[Yegor Yefremov]

Hi Arnd,

On Thu, May 12, 2022 at 12:20 PM Yegor Yefremov
<yegorslists at googlemail.com> wrote:
>
> Hi Arnd,
>
> On Thu, May 12, 2022 at 10:43 AM Arnd Bergmann <arnd at arndb.de> wrote:
> >
> > On Thu, May 12, 2022 at 7:41 AM Tony Lindgren <tony at atomide.com> wrote:
> > > * Yegor Yefremov <yegorslists at googlemail.com> [220511 14:16]:
> > > > On Thu, May 5, 2022 at 7:08 AM Tony Lindgren <tony at atomide.com> wrote:
> > > > > * Yegor Yefremov <yegorslists at googlemail.com> [220504 10:35]:
> > > > > > Hi Tony, all,
> > > > > >
> > > > > > since kernel 5.18.x (5.17.x doesn't show this behavior), the system
> > > > > > stalls as soon as I invoke the following commands (initializing
> > > > > > USB-to-CAN converter):
> > > > > >
> > > > > > slcand -o -s8 -t hw -S 3000000 /dev/ttyUSB0
> > > > > > ip link set slcan0 up
> >
> > Oh, I missed this part at first and only looked at the backtrace.
> > Which CAN driver
> > are you using? It's likely a problem in the kernel driver.
>
> I am using the slcan driver [1].
>
> > CONFIG_DMA_API_DEBUG is still likely to pinpoint the bug, but I might also
> > just see it by looking at the right source file.
>
> I'll try to get more debug info with CONFIG_DMA_API_DEBUG.

DMA_API_DEBUG showed nothing new. But disabling the CPUfreq driver
"solved" the problem. I have tried different governors and got these
two groups:

ondemand, schedutil - cause the problem
conservative, powersave, performance and userspace - don't cause the problem

So far, I have only seen the same debug output that I've initially
sent and in most cases, the system stalls without the output.

Yegor
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/can/slcan.c?h=v5.18-rc6
>
> Yegor
> >        Arnd