When the RTOS is present and the tickless mode is not implemented, it is
expected that the next tick issued by the Systick timer will wake up the MCU.
However nothing prevents an implementation of the ARM architecture to gate the
systick clock signal upon sleep entry.
Therefore on those targets sleep shall be prohibited if the RTOS is present and the
tickless mode is not implemented.
To ease life of porters , a new option has been added in the device add list:
STCLK_OF_DURING_SLEEP. This option expose that the target turn of the systick
clock during sleep.
Targets which exhibit such behavior shall add this define in their device_has list.
Sleep manager provides API to lock/unlock deepsleep. This API allows a user to
control deep sleep.
This API should be done via atomic operations (to be IRQ/thread safe).
Steven Cartmell
Bartek Szatkowski
Vincent Coubard
Senthil Ramakrishnan
Martin Kojtal
Christopher Haster