[PATCH] powerpc, wdt: disable ratelimiting when disabling interrupts

[Rasmus Villemoes]

On powerpc, time as measured by get_timer() ceases to pass when
interrupts are disabled (since on powerpc get_timer() returns the
value of a volatile variable that gets updated via a timer
interrupt). That in turn means the watchdog_reset() function provided
by CONFIG_WDT ceases to work due to the ratelimiting it imposes.

Normally, interrupts are just disabled very briefly. However, during
bootm, they are disabled for good prior to decompressing the kernel
image, which can be a somewhat time-consuming operation. Even when we
manage to decompress the kernel and do the other preparation steps and
hand over control to the kernel, the kernel also takes some time
before it is ready to assume responsibility for handling the
watchdog. The end result is that the board gets reset prematurely.

The ratelimiting isn't really strictly needed (prior to DM WDT, no
such thing existed), so just disable it when we know that time no
longer passes and have watchdog_reset() (e.g. called from
decompression loop) unconditionally reset the watchdog timer.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
---

I previously sent a patch to change the ratelimiting to be based on
get_ticks() instead of get_timer(), but that has gone nowhere
[1]. This is an alternative which only affects powerpc (and only
boards that have enabled CONFIG_WDT). I hope the watchdog maintainers
will accept at least one of these, or suggest a third alternative, so
I don't have to keep some out-of-tree patch applied without knowing if
that's the direction upstream will take.

[1] https://patchwork.ozlabs.org/project/uboot/patch/20200605111657.28773-1-rasmus.villemoes@prevas.dk/



 arch/powerpc/lib/interrupts.c | 3 +++
 drivers/watchdog/wdt-uclass.c | 8 +++++++-
 include/wdt.h                 | 6 ++++++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/lib/interrupts.c b/arch/powerpc/lib/interrupts.c
index 73f270002c..5c5b5fd7ff 100644
--- a/arch/powerpc/lib/interrupts.c
+++ b/arch/powerpc/lib/interrupts.c
@@ -11,6 +11,7 @@
 #include <irq_func.h>
 #include <asm/processor.h>
 #include <watchdog.h>
+#include <wdt.h>
 #ifdef CONFIG_LED_STATUS
 #include <status_led.h>
 #endif
@@ -43,6 +44,7 @@ static __inline__ void set_dec (unsigned long val)
 void enable_interrupts(void)
 {
 	set_msr (get_msr () | MSR_EE);
+	watchdog_ratelimit(1);
 }
 
 /* returns flag if MSR_EE was set before */
@@ -50,6 +52,7 @@ int disable_interrupts(void)
 {
 	ulong msr = get_msr ();
 
+	watchdog_ratelimit(0);
 	set_msr (msr & ~MSR_EE);
 	return ((msr & MSR_EE) != 0);
 }
diff --git a/drivers/watchdog/wdt-uclass.c b/drivers/watchdog/wdt-uclass.c
index 0603ffbd36..b70a9d50b8 100644
--- a/drivers/watchdog/wdt-uclass.c
+++ b/drivers/watchdog/wdt-uclass.c
@@ -131,6 +131,12 @@ int wdt_expire_now(struct udevice *dev, ulong flags)
 	return ret;
 }
 
+static int ratelimit = 1;
+void watchdog_ratelimit(int on)
+{
+	ratelimit = on;
+}
+
 #if defined(CONFIG_WATCHDOG)
 /*
  * Called by macro WATCHDOG_RESET. This function be called *very* early,
@@ -148,7 +154,7 @@ void watchdog_reset(void)
 
 	/* Do not reset the watchdog too often */
 	now = get_timer(0);
-	if (time_after(now, next_reset)) {
+	if (!ratelimit || time_after(now, next_reset)) {
 		next_reset = now + reset_period;
 		wdt_reset(gd->watchdog_dev);
 	}
diff --git a/include/wdt.h b/include/wdt.h
index bc242c2eb2..9ba1e62dcf 100644
--- a/include/wdt.h
+++ b/include/wdt.h
@@ -107,4 +107,10 @@ struct wdt_ops {
 
 int initr_watchdog(void);
 
+#if CONFIG_IS_ENABLED(WDT)
+void watchdog_ratelimit(int on);
+#else
+static inline void watchdog_ratelimit(int on) { }
+#endif
+
 #endif  /* _WDT_H_ */
-- 
2.29.2