wes3 commented on a change in pull request #1299: [RFC] [NRF52] Remove uint64_t
div in watchdog init
URL: https://github.com/apache/mynewt-core/pull/1299#discussion_r205834969
##########
File path: hw/mcu/nordic/nrf52xxx/src/hal_watchdog.c
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@@ -44,13 +44,20 @@ nrf52_wdt_irq_handler(void)
int
hal_watchdog_init(uint32_t expire_msecs)
{
- uint64_t expiration;
-
NRF_WDT->CONFIG = WDT_CONFIG_SLEEP_Msk;
- /* Convert msec timeout to counts of a 32768 crystal */
- expiration = ((uint64_t)expire_msecs * 32768) / 1000;
- NRF_WDT->CRV = (uint32_t)expiration;
+ if (expire_msecs >= 1048576) {
+ /* watchdog with more than 17 minutes? */
+ assert(0);
+ } else {
+ uint32_t e = expire_msecs, rtc = 32768, d = 1000;
+ while (e >= 131072) {
+ e /= 2;
+ rtc /= 2;
+ d /= 2;
Review comment:
I think you could do this in the following manner and get much more range. I
probably should have done this from the start but did not worry about the
65-bit divide. We are trying to do the following: (x * 32768) / 1000. This is
the same as doing this: x * 32.768. Since we do not want to use floating point
you can do this: (x * 32) + ((x * 768) / 1000) which is also this: (x * 32) +
((x * 96) / 125). You can then get much more range.
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