[PR] Rewrite adjtime() implementation to work for RTC and tickless kernel [nuttx]

["PetteriAimonen (via GitHub)" <gi...@apache.org>]

PetteriAimonen opened a new pull request, #11186:
URL: https://github.com/apache/nuttx/pull/11186

   ## Summary
   
   Previous `adjtime()` implementation was limited to adjusting system timer tick period. This commit reimplements the internals to use a kernel watchdog timer. Platform-independent part of the code now works also for adjusting hires RTC and tickless timer rate.
   
   Currently there are no in-tree architecture implementations for high-res RTC nor tickless timer adjustments, but the API is now available.
   
   Other improvements:
   
   - Support query of remaining adjustment by passing NULL to first argument of adjtime(). This matches Linux behavior.
   
   - Improve resolution available for architecture driver, previously limited to 1 microsecond per tick. Now 1 nanosecond per second on API level.  For ARM SysTick based drivers the hardware resolution is 1 clock cycle per tick.
   
   ## Impact
   
   User code facing API is unchanged. Architecture code API has changed:
   `up_adj_timer_period()` is replaced by `up_adjtime()`.
   
   The in-tree implementations for STM32 and SAMv7 architectures have been updated to match.
   
   ## Testing
   
   Tested on custom STM32F407 board in classic systick configuration, and also with `CONFIG_RTC_HIRES=y` against custom RTC driver.
   


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Re: [PR] Rewrite adjtime() implementation to work for RTC and tickless kernel [nuttx]

["xiaoxiang781216 (via GitHub)" <gi...@apache.org>]

xiaoxiang781216 merged PR #11186:
URL: https://github.com/apache/nuttx/pull/11186


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