3.3.3. Low Power Modes

3.3.3.1. Overview

Note

For this release, both of the documented low power modes below require special steps which have been documented in System Suspend Mode Workarounds. This includes the steps to choose the system suspend mode and how to wakeup the system.

The following sections describe a high-level description of the different low power modes (LPM) of the device. If your application requires inactive power management, you must determine which low power mode described below satisfies your requirements. Each mode must be evaluated based on power consumption and latency (the time it takes to wakeup to active mode) requirements. Specific values are detailed in the device-specific data sheet. As part of this SDK offering, Texas Instruments has added support for the following low power modes (ordered from lowest power consumption to highest power consumption):

1. RTC Only Plus DDR

2. Deep Sleep

3.3.3.2. RTC Only Plus DDR

RTC Only + DDR mode is the deepest low power mode that allows the system to enter a state of lowest power consumption while still retaining the DDR RAM context.

In order to enter RTC Only + DDR mode,

root@am62lxx-evm:~# echo mem > /sys/power/state
[   67.335138] PM: suspend entry (deep)
[   67.358190] Filesystems sync: 0.019 seconds
[   67.363206] Freezing user space processes
[   67.368991] Freezing user space processes completed (elapsed 0.001 seconds)
[   67.376038] OOM killer disabled.
[   67.379271] Freezing remaining freezable tasks
[   67.384973] Freezing remaining freezable tasks completed (elapsed 0.001 seconds)
[   67.392398] printk: Suspending console(s) (use no_console_suspend to debug)
NOTICE:  bl1_plat_arch_setup arch setup
NOTICE:  Booting Trusted Firmware
NOTICE:  BL1: v2.12.0(release):11.00.04-7-gaa3963759-dirty
NOTICE:  BL1: Built : 15:56:37, Feb 25 2025
NOTICE:  lpdd4_init <--
NOTICE:  DDR ram size =80000000
NOTICE:  bl1_platform_setup DDR init done
NOTICE:  k3_bl1_handoff sent message to tifs
ERROR:   Wake up src 0x0
ERROR:   Wake up interrupt 0xc
[   67.405953] Disabling non-boot CPUs ...
[   67.408032] psci: CPU1 killed (polled 0 ms)
[   67.408974] Enabling non-boot CPUs ...
[   67.409281] Detected VIPT I-cache on CPU1
[   67.409330] GICv3: CPU1: found redistributor 1 region 0:0x0000000001860000
[   67.409393] CPU1: Booted secondary processor 0x0000000001 [0x410fd034]
[   67.410371] CPU1 is up
[   67.446329] OOM killer enabled.
[   67.449479] Restarting tasks ... done.
[   67.454324] random: crng reseeded on system resumption
[   67.459689] PM: suspend exit

3.3.3.3. DeepSleep

DeepSleep AKA Suspend-to-RAM is a low-power mode that allows the SoC to retain its state in RAM while the processor is turned off. DeepSleep mode is typically used during inactivity when the user requires very low power while waiting for an event that requires processing or higher performance. DeepSleep is a low power mode which still includes DDR in self-refresh, so wakeup events do not require a full cold boot, significantly reducing wakeup latencies. Since the power to Always-On power domains are ON throughout DeepSleep, power to key modules such as GPIO and others is maintained to allow wakeup events to exit out of this mode.

In order to enter DeepSleep,

root@am62lxx-evm:~# echo mem > /sys/power/state
[   88.507502] PM: suspend entry (deep)
[   88.530523] Filesystems sync: 0.019 seconds
[   88.537597] Freezing user space processes
[   88.543218] Freezing user space processes completed (elapsed 0.001 seconds)
[   88.550275] OOM killer disabled.
[   88.553518] Freezing remaining freezable tasks
[   88.559139] Freezing remaining freezable tasks completed (elapsed 0.001 seconds)
[   88.566570] printk: Suspending console(s) (use no_console_suspend to debug)
ERROR:   Wake up src 0x80
ERROR:   Wake up interrupt 0xc
[   88.591181] Disabling non-boot CPUs ...
[   88.593309] psci: CPU1 killed (polled 0 ms)
[   88.594858] Enabling non-boot CPUs ...
[   88.595327] Detected VIPT I-cache on CPU1
[   88.595379] GICv3: CPU1: found redistributor 1 region 0:0x0000000001860000
[   88.595446] CPU1: Booted secondary processor 0x0000000001 [0x410fd034]
[   88.596420] CPU1 is up
[   88.634778] OOM killer enabled.
[   88.637926] Restarting tasks ... done.
[   88.642801] random: crng reseeded on system resumption
[   88.649913] PM: suspend exit
root@am62lxx-evm:~#