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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 f9fb4c462b
commit 17bd5cce7e
4 changed files with 12 additions and 3 deletions
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9
README
View File

@ -747,6 +747,15 @@ The following options need to be configured:
SoC, then define this variable and provide board
specific code for the "hw_watchdog_reset" function.
CONFIG_SYS_WATCHDOG_FREQ
Some platforms automatically call WATCHDOG_RESET()
from the timer interrupt handler every
CONFIG_SYS_WATCHDOG_FREQ interrupts. If not set by the
board configuration file, a default of CONFIG_SYS_HZ/2
(i.e. 500) is used. Setting CONFIG_SYS_WATCHDOG_FREQ
to 0 disables calling WATCHDOG_RESET() from the timer
interrupt.
- Real-Time Clock:
When CONFIG_CMD_DATE is selected, the type of the RTC

2
arch/m68k/lib/time.c
View File

@ -71,7 +71,7 @@ void dtimer_interrupt(void *not_used)
timestamp++;
#if defined(CONFIG_WATCHDOG) || defined (CONFIG_HW_WATCHDOG)
if ((timestamp % (CONFIG_SYS_WATCHDOG_FREQ)) == 0) {
if (CONFIG_SYS_WATCHDOG_FREQ && (timestamp % (CONFIG_SYS_WATCHDOG_FREQ)) == 0) {
WATCHDOG_RESET ();
}
#endif /* CONFIG_WATCHDOG || CONFIG_HW_WATCHDOG */

2
arch/powerpc/lib/interrupts.c
View File

@ -80,7 +80,7 @@ void timer_interrupt(struct pt_regs *regs)
timestamp++;
#if defined(CONFIG_WATCHDOG) || defined (CONFIG_HW_WATCHDOG)
if ((timestamp % (CONFIG_SYS_WATCHDOG_FREQ)) == 0)
if (CONFIG_SYS_WATCHDOG_FREQ && (timestamp % (CONFIG_SYS_WATCHDOG_FREQ)) == 0)
WATCHDOG_RESET ();
#endif /* CONFIG_WATCHDOG || CONFIG_HW_WATCHDOG */

2
drivers/timer/mpc83xx_timer.c
View File

@ -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 */