Overview

For Power Management Architecture and Low Power Modes, please refer to the relevant chapters in Power Saving Guide .

Zephyr Support Status

Management Mechanisms:

Supported: System-Managed Device Power Management
Not Supported: Device Runtime Power Management
Device-level management under System-Managed Management is not yet supported

Low Power Levels:

PM_STATE_SUSPEND_TO_IDLE: Corresponds to Clock Gating
PM_STATE_SUSPEND_TO_RAM0: Corresponds to Power Gating
Default: CPU idle (WFI)

Wake Source Support Status:

Device	State
BT_WAKE_HOST	YES
CAN	YES
SDIO_HOST	YES
RMII	YES
CAPTOUCH	YES
ADC	YES
RTC	YES
GPIO	YES
UART_LOG	YES
UART	YES
Timer	YES
IWDG	YES
SDIO_WIFI	NO
BT_SCB	NO
SDIO_BT	NO
AON_WAKEPIN	NO
AON_TIM	NO
PWR_DOWN	NO
USB	NO
BOR	NO

Low Power Entry Strategies

Zephyr supports two strategies for entering low power modes: Residency Based and Application Defined. Refer to Power Management Policies.

We have added additional check logic based on Zephyr’s Residency Based policy. The process is as follows:

First, check that modules such as BT/WiFi allow entering low power mode
Then compare expire ticks with the predefined states in DTS. If the residency time is satisfied, enter the selected state. For example, the following state definitions:
```
power-states {
  pm_cg: pm_cg {
    compatible = "zephyr,power-state";
    power-state-name = "suspend-to-idle";
    min-residency-us = <3000>;
    exit-latency-us = <2000>;
  };
  pm_pg: pm_pg {
    compatible = "zephyr,power-state";
    power-state-name = "suspend-to-ram";
    min-residency-us = <5000>;
    exit-latency-us = <2500>;
  };
};
```
Iterate through all states. When the idle time is greater than min-residency-us + exit-latency-us, that state is selected, until the condition is no longer met. For more details, refer to Residency Based Policy.

Sleep and Wake-up Flow

The following diagram mainly illustrates the flow of the AP (Zephyr OS). For how the AP coordinates with the NP core before entering sleep and during the wake-up process, please refer to Power Saving Developer Guide .

PG:
CG: