On the MPC8309-derived board I'm currently working on, the current rate-limiting logic in the generic watchdog_reset function poses two problems:
First, the hard-coded limit of 1000ms is too large for the external GPIO-triggered watchdog we have.
Second, in the SPL, the decrementer interrupt is not enabled, so the get_timer() call calls always returns 0, so wdt_reset() is never actually called. Enabling that interrupt (i.e. calling interrupt_init() somewhere in my early board code) is a bit problematic, since U-Boot proper gets loaded to address 0, hence overwriting exception vectors - and the reason I even need to care about the watchdog in the SPL is that the signature verification takes a rather long time, so just disabling interrupts before loading U-Boot proper doesn't work.
Both problems can be solved by allowing the board to override the rate-limiting logic. For example, in my case I will implement the function in terms of get_ticks() (i.e. the time base registers on PPC) which do not depend on interrupts, and use a threshold of gd->bus_clk / (4*16) ticks (~62ms).
Signed-off-by: Rasmus Villemoes rasmus.villemoes@prevas.dk ---
This is on top of https://patchwork.ozlabs.org/patch/1242772/, but it's obviously trivial to do on master instead.
drivers/watchdog/wdt-uclass.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-)
diff --git a/drivers/watchdog/wdt-uclass.c b/drivers/watchdog/wdt-uclass.c index 309a0e9c5b..ad53e86b80 100644 --- a/drivers/watchdog/wdt-uclass.c +++ b/drivers/watchdog/wdt-uclass.c @@ -67,6 +67,19 @@ int wdt_expire_now(struct udevice *dev, ulong flags) }
#if defined(CONFIG_WATCHDOG) +__weak int watchdog_reset_ratelimit(void) +{ + static ulong next_reset; + ulong now; + + now = get_timer(0); + if (time_after(now, next_reset)) { + next_reset = now + 1000; /* reset every 1000ms */ + return 1; + } + return 0; +} + /* * Called by macro WATCHDOG_RESET. This function be called *very* early, * so we need to make sure, that the watchdog driver is ready before using @@ -74,19 +87,13 @@ int wdt_expire_now(struct udevice *dev, ulong flags) */ void watchdog_reset(void) { - static ulong next_reset; - ulong now; - /* Exit if GD is not ready or watchdog is not initialized yet */ if (!gd || !(gd->flags & GD_FLG_WDT_READY)) return;
/* Do not reset the watchdog too often */ - now = get_timer(0); - if (time_after(now, next_reset)) { - next_reset = now + 1000; /* reset every 1000ms */ + if (watchdog_reset_ratelimit()) wdt_reset(gd->watchdog_dev); - } } #endif