Low-Power Application

This chapter describes the GK7206 low-power (Power Management, PM) application example — sample_pm. The application demonstrates the chip's power management features, including entering low-power mode, the wake-up flow, and the related register configurations.

The application source code is located in the SDK directory sample/pm/. It is a reference example demonstrating the low-power features.

1 Application Overview

1.1 Features

• Low-power mode demonstration: demonstrates the complete flow of entering and exiting the chip's low-power mode
• Loop testing: supports repeating the test a specified number of times
• Status printing: prints status information when entering/exiting low-power mode
• No hardware dependency: no sensor or other peripherals required

1.2 Technical Specifications

Parameter	Value
Command format	./sample_pm [test_count]
test_count	Number of loop iterations (optional, default 1)
Memory footprint	Minimal
Kernel module	requires xm_pm.ko

1.3 Directory Structure

sample/pm/
├── Makefile              # Build script
└── sample_pm.c           # Main program

2 Build and Deployment

2.1 Prerequisites

Before building this application, make sure the following preparations have been completed:

1. SDK environment is set up: follow SDK Compilation to set up the cross-compilation toolchain and SDK configuration
2. Kernel module is loaded: xm_pm.ko is loaded together with the media stack

2.2 Build the Application

# Enter the sample directory
cd <SDK_PATH>/sample

# Build the pm sample
make -C pm clean && make -C pm

Or build from the top level:

make -C sample all

2.3 Deploy to the Board

# Transfer to the development board via SCP
scp sample/pm/sample_pm root@<board IP>:/tmp/

# Or download via TFTP
tftp -g -r sample_pm <board IP>

2.4 Run the Application

# Add execute permission
chmod +x /tmp/sample_pm

# Run (once by default)
./sample_pm 1

# Loop 5 times
./sample_pm 5

2.5 Expected Output

Single test (./sample_pm 1)

sample_pm test start
test_count = 1
pm test 0
pm init success
pm enter sleep mode
pm exit sleep mode
pm deinit success
program exit normally!

Success indicator: program exit normally!, with no error messages.

Loop test (./sample_pm 5)

sample_pm test start
test_count = 5
pm test 0
pm init success
pm enter sleep mode
pm exit sleep mode
pm deinit success
pm test 1
pm init success
pm enter sleep mode
pm exit sleep mode
pm deinit success
pm test 2
pm init success
pm enter sleep mode
pm exit sleep mode
pm deinit success
pm test 3
pm init success
pm enter sleep mode
pm exit sleep mode
pm deinit success
pm test 4
pm init success
pm enter sleep mode
pm exit sleep mode
pm deinit success
program exit normally!

Success indicator: exits normally after the specified number of iterations, showing program exit normally!.

Running without arguments (./sample_pm)

sample_pm test start
test_count = 1
pm test 0
pm init success
pm enter sleep mode
pm exit sleep mode
pm deinit success
program exit normally!

Default behavior: without arguments, the loop runs once by default.

Error cases

pm init failed

Cause: the PM module is not loaded or initialization failed Solution: check whether xm_pm.ko is loaded

pm enter sleep mode failed

Cause: failed to enter low-power mode Solution: check the system state and whether another process is blocking it

3 Internal Execution Logic in Detail

3.1 Application Architecture

This application uses a simple loop-test architecture:

int main(int argc, char *argv[])
{
    int test_count = 1;
    int i;

    // Parse the command-line arguments
    if (argc > 1) {
        test_count = atoi(argv[1]);
    }

    printf("sample_pm test start\n");
    printf("test_count = %d\n", test_count);

    // Loop test
    for (i = 0; i < test_count; i++) {
        printf("pm test %d\n", i);
        sample_pm_test();
    }

    printf("program exit normally!\n");
    return 0;
}

3.2 PM Test Flow

The sample_pm_test() function demonstrates the complete low-power flow:

xmedia_s32 sample_pm_test(void)
{
    xmedia_s32 ret;

    // Step 1: Initialize the PM module
    ret = xmedia_pm_init();
    if (ret != XMEDIA_SUCCESS) {
        printf("pm init failed\n");
        return ret;
    }
    printf("pm init success\n");

    // Step 2: Enter low-power mode
    ret = xmedia_pm_enter_sleep_mode();
    if (ret != XMEDIA_SUCCESS) {
        printf("pm enter sleep mode failed\n");
        xmedia_pm_exit();
        return ret;
    }
    printf("pm enter sleep mode\n");

    // Step 3: Exit low-power mode
    ret = xmedia_pm_exit_sleep_mode();
    if (ret != XMEDIA_SUCCESS) {
        printf("pm exit sleep mode failed\n");
        xmedia_pm_exit();
        return ret;
    }
    printf("pm exit sleep mode\n");

    // Step 4: Clean up
    xmedia_pm_exit();
    printf("pm deinit success\n");

    return XMEDIA_SUCCESS;
}

3.3 Low-Power Modes

GK7206 supports several low-power modes:

Mode	Description	Wake-up sources
Light sleep	Disables some clocks, RAM retained	GPIO interrupt, timer
Deep sleep	Disables more clocks, lowers voltage	GPIO interrupt, RTC
Power off	Shuts down most power supplies, only critical circuits remain	Power button, RTC

This application demonstrates light sleep mode, which suits scenarios that require fast wake-up.

4 Key Programming Points

4.1 Initialization and Cleanup

// Initialize the PM module
xmedia_pm_init();

// Clean up the PM module
xmedia_pm_exit();

4.2 Enter/Exit Low-Power Mode

// Enter low-power mode
xmedia_pm_enter_sleep_mode();

// Exit low-power mode
xmedia_pm_exit_sleep_mode();

4.3 Error Handling

Check the return value of every API call:

ret = xmedia_pm_enter_sleep_mode();
if (ret != XMEDIA_SUCCESS) {
    printf("pm enter sleep mode failed\n");
    // Clean up
    xmedia_pm_exit();
    return ret;
}

5 Troubleshooting

Problem	Possible cause	Solution
pm init failed	PM module not loaded	Check whether xm_pm.ko is loaded
pm enter sleep mode failed	Cannot enter low-power mode	Check the system state and whether another process blocks it
pm exit sleep mode failed	Wake-up failed	Check the wake-up source configuration
Cannot wake up	Wake-up source not configured	Configure GPIO or RTC as the wake-up source

6 References

• MPP Media Processing Platform
• SDK Compilation Guide
• Encryption/Decryption Application
• ADC Acquisition Application