NuttX provides the wdog module to implement timers for the scheduler.
While it is lightweight and efficient, wdog only supports tick-level timers,
typically in milliseconds. Although the tick duration can be configured,
setting it to microsecond or nanosecond resolution is not practical.
Doing so may cause an interrupt storm, where the CPU is constantly
occupied handling tick interrupts.
To address this limitation, a new hrtimer module is introduced.
It coexists with the wdog module, providing both tick-level timers
for wdog and high-resolution timers (nanosecond-level) directly to users.
Signed-off-by: Chengdong Wang <wangchengdong@lixiang.com>
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