LPM UART Wakeup

Introduction

This example shows usage of RP Message APIs to exchange messages between linux on cortex-A CPU and RTOS/NORTOS CPUs. This example also demonstrates the capability of MCU UART input event to wake the entire SOC in MCU Only low power mode.

Attention

Low power mode is supported only on the Linux SPL boot flow. SBL bootflow does not support low power mode (LPM)

In this example,

  • We first confirm the functionality of IPC Message exchange between Linux and other cores. Refer IPC RP Message Linux Echo. This is necessary to ensure that IPC is working correctly, which is a requirement for entering low power mode.

  • This example provides support for graceful shutdown of the remote core (MCU R5F). Refer Graceful shutdown of remote cores from Linux

  • This example provides support for MCU only low power mode support on the MCU core (MCU R5F). To run MCU-only low power mode, refer MCU only LPM

  • This example provides support for other low power modes on the remote core (MCU R5F). To run MCU-only low power mode, refer Deep Sleep LPM

The example integrates bootloading functionality with SBL on OSPI bootmedia. It also integrates Device manager functionality. The SBL stage 2 thread boots all the cores along with HLOS like Linux. Refer SBL Booting Linux From OSPI for boot flow sequence.

Supported Combinations

Parameter

Value

CPU + OS

mcu-r5fss0-0 freertos

Toolchain

ti-arm-clang

Board

am62px-sk

Example folder

examples/lpm/lpm_mcu_dmtimer_wakeup

Steps to Run the Example

  • When using CCS projects to build, import the system CCS project and build it using the CCS project menu (see Using SDK with CCS Projects). This will build all the dependant CPU projects as well

  • When using makefiles to build, build the system makefile using make command (see Using SDK with Makefiles). This will build all the dependant CPU makefiles as well.

  • To run this demo, Linux needs to run on the Cortex A-core. Refer to Processor SDK Linux user guide to load and run this example.

  • This example integrates SBL on OSPI bootmedia which needs to be flashed on the EVM flash, along with sample application images for MCU R5 CPUs, HSM M4F and Linux Appimage.

  • For HS-FS device, use default_sbl_ospi_linux_hs_fs.cfg as the cfg file.

  • To flash to the EVM, refer to Flash a Hello World example .

  • Example, assuming SDK is installed at C:/ti/mcu_plus_sdk and this example and IPC application is built using makefiles, and Linux Appimage is already created, in Windows,

      cd C:/ti/mcu_plus_sdk/tools/boot
  python uart_uniflash.py -p COM13 --cfg=C:/ti/mcu_plus_sdk/tools/boot/sbl_prebuilt/{{ VAR_BOARD_NAME_LOWER }}/default_sbl_ospi_linux_hs_fs.cfg

  • If Linux PC is used, assuming SDK is installed at ~/ti/mcu_plus_sdk

      cd ~/ti/mcu_plus_sdk
  python uart_uniflash.py -p /dev/ttyUSB0 --cfg=~/ti/mcu_plus_sdk/tools/boot/sbl_prebuilt/{{ VAR_BOARD_NAME_LOWER }}/default_sbl_ospi_linux_hs_fs.cfg

  • Switch to OSPI NOR BOOT MODE and power on the EVM.

Attention

As the wake-up R5 is the device manager, it needs to be started by the SBL. So it can not be loaded through CCS. It should be flashed and booted through SBL.

MCU only LPM

  • Set the wake up resume latency as 100ms for CPU0 on the linux kernel by running the following command. When the resume latency value is less, suspending the kernel will go to MCU only sleep mode.

$ echo 100000 > /sys/devices/system/cpu/cpu0/power/pm_qos_resume_latency_us

  • Go to MCU only low power mode by running the following command on the linux.

$ echo mem > /sys/power/state

  • After this the following message will appear on the MCU UART.

[LPM UART WAKEUP] Next MCU mode is 1
[LPM UART WAKEUP] Suspend request to MCU-only mode received
[LPM UART WAKEUP] Press a single key on this terminal to resume the kernel from MCU only mode

  • Then type any key on the MCU UART to resume the kernel from LPM.

[LPM UART WAKEUP] Key pressed. Notifying DM to wakeup main domain
[LPM UART WAKEUP] Main domain resumed due to MCU UART

Deep Sleep LPM

  • Go to Deep Sleep low power mode by running the following command on the linux.

$ echo mem > /sys/power/state

  • After this, the following message will appear on the MCU UART.

[LPM UART WAKEUP] Next MCU mode is 0
[LPM UART WAKEUP] Closing all drivers and going to WFI ... !!!

  • Then to resume the kernel from LPM, press any key on MCU UART. This will trigger the IO Daisy chain wakeup, which will resume the kernel. The following message will appear on the MCU UART

[LPM UART WAKEUP] Example Application Started...
[LPM UART WAKEUP] Remote Core waiting for messages at end point 13 ... !!!
[LPM UART WAKEUP] Remote Core waiting for messages at end point 14 ... !!!

See Also

Sample Output

There is no direct output from the RTOS/NORTOS CPUs on the UART or CCS console. The output is seen on the Linux console on Cortex-A CPU.