This flag is an indication to the timer driver that the OS doesn't
care about rollover conditions of the tick count while idling, so the
system doesn't need to wake up once per counter flip[1]. Obviously in
that circumstance values returned from k_uptime_get_32() are going to
be wrong, so the implementation had an assert to check for misuse.
But no one understood that from the docs, so the only place these APIs
were used in practice were as "guards" around code that needed to call
k_uptime_get_32(), even though that's 100% wrong per docs!
Clarify the docs. Remove the incorrect guards. Change the flag to
initialize to true so that uptime isn't broken-by-default in tickless
mode. Also move the implemenations of the functions out of the
header, as there's no good reason for these to need to be inlined.
[1] Which can be significant. A 100MHz ARM using the 24 bit SysTick
counter rolls over at about 6 Hz, and if it had to come out of
idle at that rate it would be a significant power issue that would
swamp the gains from tickless. Obviously systems with slow
counters like nRF or 64 bit ones like RISC-V or x86's TSC aren't
as affected.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
b8ffd9acd6