[PATCH] common: board_r: Initialize interrupts before watchdog

[Simon Glass]

Hi J,

On Sat, 22 Feb 2025 at 11:58, J. Neuschäfer <j.ne at posteo.net> wrote:
>
> (CC'ing Mario Six regarding MPC83xx timer driver in U-Boot)
>
> On Thu, Feb 20, 2025 at 06:49:58AM -0700, Simon Glass wrote:
> > Hi J,
> >
> > On Tue, 18 Feb 2025 at 08:55, J. Neuschäfer via B4 Relay
> > <devnull+j.ne.posteo.net at kernel.org> wrote:
> > >
> > > From: "J. Neuschäfer" <j.ne at posteo.net>
> > >
> > > On some platforms, initializing the watchdog driver enables a timer
> > > interrupt. This of course requires the interrupt handlers to be
> > > properly initialized, otherwise U-Boot may crash or run the timer
> > > interrupt handler of a previous bootloader stage.
> > >
> > > To account for such systems, always initialize interrupts
> > > (arch_initr_trap) before the watchdog (initr_watchdog).
> > >
> > > This problem was observed on a PowerPC MPC83xx board.
> > >
> > > Signed-off-by: J. Neuschäfer <j.ne at posteo.net>
> > > ---
> > > NOTE: This approach seems safe and fine to me, but an argument could be
> > >       made that this should be fixed in the platform-specific drivers
> > >       instead.  Please let me know what you think.
> > >
> > >
> > > Rough stack trace (not sure if it should be part of the commit message):
> > >
> > >   initr_watchdog                (drivers/watchdog/wdt-uclass.c)
> > >     device_probe(wdt at 200)
> > >       device_probe(timer)
> > >         mpc8xxx_wdt_start       (drivers/watchdog/mpc8xxx_wdt.c)
> > >           set_msr(get_msr() | MSR_EE);
> > >
> > >   arch_initr_trap               (arch/powerpc/lib/traps.c)
> > >     trap_init                   (arch/powerpc/cpu/mpc83xx/start.S)
> > > ---
> > >  common/board_r.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/common/board_r.c b/common/board_r.c
> > > index 179259b00de81f7ba9802fc5288e7c2b6e6f381a..f711cd237ae76d80ca2413017bfe131656f44180 100644
> > > --- a/common/board_r.c
> > > +++ b/common/board_r.c
> > > @@ -652,11 +652,11 @@ static init_fnc_t init_sequence_r[] = {
> > >         serial_initialize,
> > >         initr_announce,
> > >         dm_announce,
> > > +       arch_initr_trap,
> > >  #if CONFIG_IS_ENABLED(WDT)
> > >         initr_watchdog,
> > >  #endif
> > >         INIT_FUNC_WATCHDOG_RESET
> > > -       arch_initr_trap,
> > >  #if defined(CONFIG_BOARD_EARLY_INIT_R)
> > >         board_early_init_r,
> > >  #endif
> > >
> > > ---
> > > base-commit: 064556910e61044f1295162ceaad600582b66cda
> > > change-id: 20250218-init-dab1fc72abd2
> > >
> > > Best regards,
> > > --
> > > J. Neuschäfer <j.ne at posteo.net>
> > >
> > >
> >
> > The driver model way of doing this would be that your UCLASS_WDT
> > driver calls uclass_first_device(UCLASS_IRQ) to make sure interrupts
> > are ready.
>
> This sounds good in principle, but would require some reworking of the
> MPC83xx interrupt infrastructure, because it currently doesn't declare a
> UCLASS_IRQ driver.
>
> > The arch_initr_trap thing should probably not be used in new code.
> > Also, we have interrupt_init() which sounds like it is similar?
>
> This isn't really *new* code, the MPC83xx platform support has been in
> U-Boot for a long time (I am touching it now due to a newly to be added
> board, though).
>
> I see various functions called interrupt_init(), one of them in
> mpc83xx_timer.c (i.e. relevant to my problems):
>
>   /*
>    * TODO(mario.six at gdsys.cc): This should really be done by timer_init, and the
>    * interrupt init should go into a interrupt driver.
>    */
>   int interrupt_init(void)
>   { ... }
>
> it seems someone has stumbled on this oddity before.
>
> Another version of interrupt_init is in arch/powerpc/lib/interrupts.c.
> Fortunately, as I just found out, my PowerPC MPC8314E board works fine
> with the generic timer/interrupt support in arch/powerpc, with
> CONFIG_TIMER=n. In other words, the problem is localized to
> CONFIG_MPC83XX_TIMER.

Thanks for all the info. So do you think you could clean this up in PowerPC?

Regards,
Simon