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allow opting out of WATCHDOG_RESET() from timer interrupt

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Having WATCHDOG_RESET() called automatically from the timer interrupt
runs counter to the idea of a watchdog device - if the board runs into
an infinite loops with interrupts still enabled, the watchdog will
never fire.

When using CONFIG_(SPL_)WDT, the watchdog_reset function is a lot more
complicated than just poking a few SOC-specific registers - it
involves accessing all kinds of global data, and if the interrupt
happens at the wrong time (say, in the middle of an WATCHDOG_RESET()
call from ordinary code), that can end up corrupting said global data.

Allow the board to opt out of calling WATCHDOG_RESET() from the timer
interrupt handler by setting CONFIG_SYS_WATCHDOG_FREQ to 0 - as that
setting is currently nonsensical (it would be compile-time
divide-by-zero), it cannot affect any existing boards.

Add documentation for both the existing and extended meaning of
CONFIG_SYS_WATCHDOG_FREQ.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
This commit is contained in:
Rasmus Villemoes
2021-04-14 09:18:22 +02:00
committed by Stefan Roese
parent 2156016294
commit 933ada560b
4 changed files with 12 additions and 3 deletions
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2
drivers/timer/mpc83xx_timer.c
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@@ -175,7 +175,7 @@ void timer_interrupt(struct pt_regs *regs)
priv->timestamp++;
#if defined(CONFIG_WATCHDOG) || defined(CONFIG_HW_WATCHDOG)
if ((priv->timestamp % (CONFIG_SYS_WATCHDOG_FREQ)) == 0)
if (CONFIG_SYS_WATCHDOG_FREQ && (priv->timestamp % (CONFIG_SYS_WATCHDOG_FREQ)) == 0)
WATCHDOG_RESET();
#endif /* CONFIG_WATCHDOG || CONFIG_HW_WATCHDOG */