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CM4 startup is controlled by the kernel through the use of remoteproc driver. CM4 software implements control of each power domain when the system is suspended or resume. It also includes polling wake-up key to enter or exit deep-sleep mode, power down or up main-domain, CA55, NPU, video codec powers, and data communication between CA55 and CM4 via virtIO as well.

Table of Contents

Table of Contents

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Output log at UART6 (set at 115,200 bps by x-boot).
Support SP7350 power manager
- Detect wake-up key
- MainPower down and up control for main-domain, CA55, NPU, video codec power down/up control
- Support DDR retention
- Support PMIC control
Support communication with CA55 via virtual l/O serial port
Support CmBacktrace to tracks and debug ARM Cortex-M4
Support Arduino hardware interface, such as SPI, I2C, UART, timer, GPIO.
Support CUnit test of SPI, I2C, UART, timer, GPIO driver

Default

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Tasks

By default, FreeRTOS of SP7350 platform is configured to run 6 tasks. In table below, we outline each task along with its location of source files and functionality.

TasksFolders or files	Files (under FreeRTOS project directory)	Descriptions
powerdown	/application/power_manager/power_down.c	power-down control
powerup	/application/power_manager/power_up.c	power-up control
wakeupkey	/application/power_manager/wakeup_key.c	Detect wake-up key
virtIOrw	/application/VirtIOSerial/vios_rw.cpp	virtual IO read/write
tmr Svc	/system/freertos/timers.c	FreeRTOS system Timer task
Idle	/system/freertos/tasks.c	FreeRTOS system Idle task

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The source files of FreeRTOS are located within the "firmware/arduino_core_sunplus/" directory under the project's top directory.

Linux Remote Processor Framework

The Linux Remote Processor Framework is a framework that allows for managing (power on, load firmware, power off) and communicating with remote processors on Linux systems. This framework is typically used in embedded or multiprocessor systems where one processor (usually the main processor) is responsible for managing and controlling the other remote processors. In addition, this framework also adds rpmsg, virtio devices for remote processors that supports this kind of communication. This way, platform-specific remoteproc drivers driver only need needs to provide a few low-level handlers, and then all rpmsg drivers will then just work. For example:

Load firmware of CM4 via Linux shell command:

Code Block
echo firmware > /sys/class/remoteproc/remoteproc/firmware

where ‘firmware’ is the firmware file (elf format) of CM4 stored at “/lib/firmware/".

Start CM4

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via

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Linux shell command:

Code Block
echo start > /sys/class/remoteproc/remoteproc0/state

Stop CM4

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via

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Linux shell command:

Code Block
echo stop > /sys/class/remoteproc/remoteproc0/state

Linux

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Remoteproc Driver

The Remoteproc remoteproc driver base on remote processor framework to implements bases on Remote Processor Framework to implement firmware loading and booting, resource allocation and management, communication support, and other functions.

Enable Enabling remoteproc driver in Linux kernel need needs to enable the configuration of (kernel feature:

CONFIG_REMOTEPROC=y and

CONFIG_SUNPLUS_REMOTEPROC=y)

in default configuration file.

Device-tree

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Nodes for

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Remoteproc Driver

Code Block

	remoteproc0: remoteproc@f800817c {
		compatible = "sunplus,sp-rproc";
		firmware = "firmware";
		reg = <0 0xf800817c 0 4>, /* mbox G258.31, cpu0 to cpu2 direct reg07 */
		      <0 0xf8800250 0 4>,
		      <0 0xf80081fc 0 4>; /* mbox G259.31, cpu2 to cpu0 direct reg07 */
		interrupt-parent = <&gic>;
		interrupts = <GIC_SPI 125 IRQ_TYPE_LEVEL_HIGH>; /* CPU2_TO_0_DIRECT_INT7 */
		resets = <&rstc RST_CM4>;
		memory-region = <&rproc_0_reserved>, <&rproc0runaddr>,<&vdev0buffer>, <&vdev0vring0>, <&vdev0vring1>;
	};

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vring0 and vring1 represent the two virtual rings of a Virtio device, typically one for sending data and the other for receiving data. These two rings pass data and control information through a set of descriptors. vbuffer represents the Virtio device's buffer, which is used to store data.

The remoteproc-related dts configuration is notes are as follows:

Code Block

	vdev0buffer: vdev0buffer@5be00000 {
		compatible = "shared-dma-pool";
		reg = <0x0 0x5be00000 0x0 0x100000>;
		no-map;
	};
	vdev0vring0: vdev0vring0@5bf00000 {
		compatible = "shared-dma-pool";
		reg = <0x0 0x5bf00000 0x0 0x10000>;
		no-map;
	};
	vdev0vring1: vdev0vring1@5bf10000 {
		compatible = "shared-dma-pool";
		reg = <0x0 0x5bf10000 0x0 0x10000>;
		no-map;
	};

RPMSG and

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Virtual IO

The RPMsg framework (Remote Processor Messaging Framework) is an implementation of remote processor messaging. It allows communication between different processors, including communication between the main processor and remote processors, and it is a VirtIO-based message bus that allows Linux kernel drivers to communicate with remote processors in the system.

Enable Enabling RPMSG and VirtIO in kernel need needs to enable the configuration of (kernel feature:

CONFIG_RPMSG=y and

CONFIG_RPMSG_VIRTIO=y)RPMSG：After

in default configuration file.

RPMSG: After CM4 is running, a device node /dev/ttyRPMSGx is generated on the kernel side, and the kernel side communicates with CM4 via /dev/ttyRPMSGx.

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VirtIO: Virtio is a standard for high-performance virtual appliances in virtualized environments, CM4 write/read VirtioSerial to transfer data to /dev/ttyRPMSGX

Build

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Image

Use “make firmware" in the root directory to compile the Freertos code，The FreeRTOS code, The output file after compilation is put in bin/firmware, . You need to copy this file it to / linux/rootfs/initramfs/disk/lib/firmware under rootfsin project directory.

This project includes several code environments, including FREERTOSFreeRTOS+Arduino (default), Arduino, and CunitCUnit, and the different code environments are determined by the configuration of the Makefile.

FREERTOSFreeRTOS+Arduino: The default compiled image is based on the Freertos FreeRTOS environment, Implemented It implements power management function for suspend /and resume processprocesses.
Arduino: set Set FREERTOS ?=0 in Makefile will compile the code environment with only arduinoArduino, not FREERTOSFreeRTOS. the The entry function of the program is in /application‘application/arduino_main.cpp’.cpp
Cunit：set CUnit: Set CUNIT ?=1 in Makefile. Compiled code contains only Cunit test code. include spi/i2c/uart/timer/gpio test units

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CUnit test code, including SPI, I2C, UART, timer, and GPIO test units.

Supported Drivers for SP7350 Platform

The source files of FreeRTOS are located within the "firmware/arduino_core_sunplus/" directory under the project's top directory. For the SP7350 platform, a wide array of device drivers is supported. These drivers are within the "system/drivers/sp7350_hal_driver/" directory. Below is a reference table detailing the drivers along with their corresponding feature descriptions:

Drivers	Files	Features
ADC (SAR12B)	sp7350_hal_adc.c	read analog voltage
Audio (I2S)	sp7350_hal_i2s.c	I2S read/write interface
GPIO driver	sp7350_hal_gpio.c	write/read gpio level
AHB DMA	sp7350_hal_dma.c	AHB DMA driver
I2C driver	sp7350_hal_i2c.c	I2C read/write interface
Mailbox	sp7350_hal_ipcc.c	trigger between CM4 and CA55
PWM	/sp7350_hal_pwm.c	output pwm
RTC	sp7350_hal_rtc.c	get rtc time and generate rtc irq
SPI	sp7350_hal_spi.c	SPI read/write interface
Timer	sp7350_hal_tim.c	get/set timer. generate timer irq
UART	sp7350_hal_uart.c	UART read/write interface
Watchdog	sp7350_hal_wdg.c	watchdog interface

Source

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Files

The source files of FreeRTOS are organized within the "firmware/arduino_core_sunplus/" directory at the project's top directory. Below is a breakdown of the main subdirectories:

Folders	Descriptions
cores/arduino	Contains the code for Arduino only
libraries/	Contains the third party source code and ‘syscall.c’
application/power_manager/	Contains power manager codes
application/VirtIOSerial/	Contains VirtIO Serial read/write codes
bin/	Output folder
system/drivers	Contains CMIS files for CM4 and SP7350 drivers
system/freertos	Contains FreeRTOS kernel files
system/Middlewares	Contains Open-amp driver (VirtIO/Remoteproc)
system/sp7350	Contains many constant definitions
variants/sp7350_evb/	Contains ldscript and config file

Example

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Files

CUnit is a C unit testing framework for unit testing C programs. It provides a set of libraries and macros for writing and executing test cases and reporting test results. CUnit tests include examples using the SP7350 peripheral interface driver. Includes examples for other drivers such as SPI, I2C, UART, GPIO and PWM. The path is:

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Set CUNIT ?=1 in Makefile to build image. The code will run from Cuint_main.cpp

FreeRTOS Log and Explanation

Line 1: The banner of CM4 firmware.

Line 2-4: Initialize remoteproc.

Line 5-6: Initialize rpmsg.

Line 7-12: Create FreeRTOS tasks.

Code Block

CM4  build @ Mar  7 2024 02:01:06
Successfully intialize remoteproc.
Initialize remoteproc successfully.
creating remoteproc virtio: 0x5be00000
initializing rpmsg vdev in mode 1
initializing rpmsg vdev done
CreateTask-viorw-result:1
CreateTask-wakeupkey-result:1
CreateTask-powerdown-result:1
CreateTask-powerup-result:1
CreateTask-IDLE-result:1
CreateTask-Tmr Svc-result:1
power down wait Semaphore !

Versions Compared

Old Version 12

New Version Current

Key

Default

Tasks

Linux Remote Processor Framework

Linux

Remoteproc Driver

Device-tree

Nodes for

Remoteproc Driver

RPMSG and

Virtual IO

Build

Image

Supported Drivers for SP7350 Platform

Source

Files

Example

Files

FreeRTOS Log and Explanation