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| -rw-r--r-- | docs/zephyr_init.md | 53 |
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diff --git a/docs/zephyr_init.md b/docs/zephyr_init.md new file mode 100644 index 0000000000..8822736efb --- /dev/null +++ b/docs/zephyr_init.md @@ -0,0 +1,53 @@ +# Zephyr OS-based EC Initialization Order + +Zephyr provides Z_INIT_ENTRY_DEFINE() & the extend macro to install the initial +function. The initialize flow for different levels would be like the following +(not very detailed): +* architecture-specific initialization +* `PRE_KERNEL_1` level +* `PRE_KERNEL_2` level +* `POST_KERNEL` level +* `APPLICATION` level +* main() + +The kernel and driver initial functions separate into specific initialize +levels. It couldn't put all initial functions in main() for the Zephyr OS-based +EC. It is also hard to maintain those initial priority which separates into +different files. + +This file defines some Zephyr OS-based EC initial priorities which have critical +sequence requirement for initializing: + +## PRE_KERNEL_1 +* Priority (0-9) - Reserved for system testability: + + The highest priority could be used in zephyr. Don't use it when system + development. Buffer it for the following system development & testing. + +* Priority (10-19) - Chip level system pre-initialization: + + These priorities in this range are used for critical chip initialization, + including determining the reset cause and initializing the battery-backed + RAM driver. Most chip drivers should only be initialized after + `PLATFORM_EC_SYSTEM_PRE_INIT`. + +* Priority (20) - PLATFORM_EC_SYSTEM_PRE_INIT: + + At this initialization priority, the CROS system checks the reset cause and + initializing the system reset flags. Any chip level drivers related to + determining the reset type must be at a higher priority. + +* TODO + +## PRE_KERNEL_2 +* TODO + +## POST_KERNEL +* TODO + +## APPLICATION +* TODO + +## main() +* TODO +* Start the tasks. |