allow opting out of WATCHDOG_RESET() from timer interrupt

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>

diff --git a/README b/README
index a565748..ad13092 100644 (file)
--- a/README
+++ b/README
@@ -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

diff --git a/arch/m68k/lib/time.c b/arch/m68k/lib/time.c
index cbe29e7..ebb2ac5 100644 (file)
--- a/arch/m68k/lib/time.c
+++ b/arch/m68k/lib/time.c
@@ -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 */

diff --git a/arch/powerpc/lib/interrupts.c b/arch/powerpc/lib/interrupts.c
index 73f2700..5ba4cd0 100644 (file)
--- a/arch/powerpc/lib/interrupts.c
+++ b/arch/powerpc/lib/interrupts.c
@@ -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 */
 

diff --git a/drivers/timer/mpc83xx_timer.c b/drivers/timer/mpc83xx_timer.c
index 9adb4b4..9522931 100644 (file)
--- a/drivers/timer/mpc83xx_timer.c
+++ b/drivers/timer/mpc83xx_timer.c
@@ -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 */