[GitHub] [incubator-nuttx] v01d commented on pull request #1726: Nrf52 tickless

[GitBox <gi...@apache.org>]

v01d commented on pull request #1726:
URL: https://github.com/apache/incubator-nuttx/pull/1726#issuecomment-687893971


   As you can see I have implemented tickless mode on RTC directly, not via arch_* facility due to the issue discussed in #1705. The implementation exposes the RTC as an alarm. This could actually be how arch_alarm can be made to work, which requires handling the overflow interrupt (this is discussed in #1725).
   
   @patacongo There is something I'm unsure about: as you can see, at the end of `up_timer_initialize()` I called `nxsched_alarm_expiration()`. If I do not do this, the 200ms scheduling alarm will not start until I for example do "sleep 1" in the console. This means that until I do so, the scheduler thinks no time has passed and thus gives a wrong value for the first alarm to up_alarm_start(). I have observed this behavior previously (and I think it is not specific to TICKLESS_ALARM) where I see the 200ms timer only starting after an initial task is launched. I'm confused how this should work. In fact, is it even necessary to keep the 200ms scheduling alarm ON even once we go back to having just one task?


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