PetteriAimonen opened a new pull request, #10827:
URL: https://github.com/apache/nuttx/pull/10827
## Summary
Prior pull request #9084 and issue #8858 added basic adjtime() support for
the SAMv7 platform.
This pull request adds support for STM32 platform.
In addition I have made a few changes to the adjtime() configuration options:
1) Previously adjustments less than 1 microsecond per tick would be
completely ignored. Now they are applied over a shorter period at
a rate of 1 us per tick.
2) Previously CLOCK_ADJTIME_PERIOD was in units of 1/100th of second.
Change to milliseconds to be more generally useful unit.
Change setting name to CLOCK_ADJTIME_PERIOD_MS to make the unit change
easier to notice.
3) Previously CLOCK_ADJTIME_SLEWLIMIT was in percentage.
Most clock crystals have better accuracy than 1%, so the minimum slew
rate was excessive. Change to CLOCK_ADJTIME_SLEWLIMIT_PPM with setting
value in parts per million.
4) No need to use floating point math in clock_adjtime.c.
## Impact
Users who have used `CLOCK_ADJTIME_PERIOD` and `CLOCK_ADJTIME_SLEWLIMIT`
settings should update their configuration. New `CLOCK_ADJTIME_PERIOD_MS` is
10x the old period value, and new `CLOCK_ADJTIME_SLEWLIMIT_PPM` is 10000 times
the old slewlimit.
## Testing
Tested on custom STM32 board with the `adjtime` example program.
## Questions
@michallenc I couldn't find the significance of the `Should be between 0.95
and 0.99.` comment that was previously in help text for `CLOCK_ADJTIME_PERIOD`.
To me it appears that the desirable value for this setting will depend entirely
on what code will be calling `adjtime()` and how often.
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