Consider the following factors to define WDT reset delay:
1. Cannot be too small. This is to avoid premature WDT reset in pieces of timeout cascading.
2. Cannot be too large. This is to pass Greentea reset_reason/watchdog_reset tests, which have e.g. 50~100 reset delay tolerance.
Original implementation doesn't enable watchdog reset in pieces of cascaded timeout, except the last one. This is to guarantee re-configuration can be in time, but in interrupt disabled scenario e.g. Hard Fault, watchdog reset can cease to be effective.
This change enables watchdog reset all the way of cascaded timeout. With trade-off, guaranteed watchdog reset function is more significant than re-configuration in time.
Chun-Chieh Li
Martin Kojtal
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