referring the ARM's Systick driver, we did the following improvements:
* use 31 bits of 32-bit counter to avoid the rare but possible
overflow of elapsed(). If 32 bits val are used, elpased() may
return a wrong value. then wrong HW cycles.
* two ways to update the correct cycles
- through systick timer irq
- when systick timer irq cann't be handled because of irq
locked/disabled, call z_timer_cycle_get_32->elapsed to update
the correct cylces. no more than one counter-wrap is allowed.
* if elapsed() is not called too long (more than one counter-wrap) from
systick tiemr irq or from z_timer_cycle_get_32. The lost of HW cycles
is unavoidable.
* some detailed discussion can be found in #24332
Signed-off-by: Wayne Ren <wei.ren@synopsys.com>
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