Challenges and Requirements

Oct 13, 2025 by wbrum.org 67 views

Introduction

When developing a product using the i.MX93 System-on-Chip (SoC), it's essential to consider the power management and shutdown mechanisms to ensure a seamless user experience. One of the requirements for our board design is to have a dedicated PSHOLD GPIO pin that is toggled to completely cut power during shutdown. However, we encountered an issue when trying to integrate this mechanism while retaining the Power State Coordination Interface (PSCI) functionality. In this article, we will explore the challenges and provide a step-by-step guide on how to integrate a PSHOLD GPIO power-off mechanism on i.MX93 while retaining PSCI functionality.

Understanding PSCI and GPIO Power-Off Mechanism

PSCI Overview

PSCI is a standardized interface for managing the power states of a system-on-chip (SoC). It provides a way for the operating system to communicate with the SoC's power management unit (PMU) to control the power states of the system. PSCI is widely used in modern SoCs, including the i.MX93, to manage power states and ensure efficient power consumption.

GPIO Power-Off Mechanism

A GPIO power-off mechanism involves using a General Purpose Input/Output (GPIO) pin to control the power supply to the system. In our case, we want to use a dedicated PSHOLD GPIO pin to toggle the power supply during shutdown. This mechanism is essential for our board design, as it allows us to completely cut power to the system during shutdown.

Challenges and Requirements

When integrating a PSHOLD GPIO power-off mechanism on i.MX93 while retaining PSCI functionality, we encountered several challenges and requirements:

PSCI and GPIO Conflict: The PSCI interface and the GPIO power-off mechanism seem to conflict with each other. We need to find a way to integrate both mechanisms without causing any issues.
Power Management: We need to ensure that the power management unit (PMU) is properly configured to support the GPIO power-off mechanism.
Shutdown Sequence: We need to define the shutdown sequence to ensure that the PSHOLD GPIO pin is toggled correctly during shutdown.

Step-by-Step Guide

To integrate a PSHOLD GPIO power-off mechanism on i.MX93 while retaining PSCI functionality, follow these steps:

Step 1: Configure PSCI

To configure PSCI, we need to enable the PSCI interface in the device tree and configure the power management unit (PMU) to support the GPIO power-off mechanism.

&soc {
    psci {
        compatible = "arm,psci-1.1";
        reg = <0x02000000 0x1000>;
        interrupts = <GIC_SPI 0 IRQ_TYPE_LEVEL_HIGH>;
        interrupt-parent = <&gic>;
        interrupt-names = "psci";
    };
};

Step 2: Configure GPIO Power-Off Mechanism

To configure the GPIO power-off mechanism, we need to define the PSHOLD GPIO pin and configure the power management unit (PMU) to support it.

&gpio {
    pshold-gpio {
        compatible = "gpio";
        reg = <PHOLD_GPIO>;
        gpio-hog;
        gpio-ranges = <&pshold-gpio 0 1>;
    };
};

Step 3: Define Shutdown Sequence

To define the shutdown sequence, we need to create a custom shutdown script that toggles the PSHOLD GPIO pin during shutdown.

#!/bin/sh

echo "PHOLD_GPIO" > /sys/class/gpio/export echo "out" > /sys/class/gpio/gpioPHOLD_GPIO/direction echo "1" > /sys/class/gpio/gpioPHOLD_GPIO/value

Step 4: Integrate PSCI and GPIO Power-Off Mechanism

To integrate PSCI and the GPIO power-off mechanism, we need to modify the PSCI interface to support the GPIO power-off mechanism.

&soc {
    psci {
        compatible = "arm,psci-1.1";
        reg = <0x02000000 0x1000>;
        interrupts = <GIC_SPI 0 IRQ_TYPE_LEVEL_HIGH>;
        interrupt-parent = <&gic>;
        interrupt-names = "psci";
        gpio-poweroff {
            compatible = "gpio-poweroff";
            reg = <PHOLD_GPIO>;
            gpio-hog;
            gpio-ranges = <&pshold-gpio 0 1>;
        };
    };
};

Conclusion

Integrating a PSHOLD GPIO power-off mechanism on i.MX93 while retaining PSCI functionality requires careful configuration and modification of the PSCI interface and the GPIO power-off mechanism. By following the step-by-step guide outlined in this article, we can ensure that the PSHOLD GPIO pin is toggled correctly during shutdown, while also retaining the PSCI functionality. This integration is essential for our board design, as it allows us to completely cut power to the system during shutdown.

Additional Resources

For more information on PSCI and GPIO power-off mechanisms, refer to the following resources:

Troubleshooting

If you encounter any issues during the integration process, refer to the following troubleshooting tips:

PSCI and GPIO Conflict: Check the PSCI interface and the GPIO power-off mechanism configuration to ensure that they are not conflicting with each other.
Power Management: Verify that the power management unit (PMU) is properly configured to support the GPIO power-off mechanism.
Shutdown Sequence: Check the shutdown sequence to ensure that the PSHOLD GPIO pin is toggled correctly during shutdown.

Frequently Asked Questions

In this Q&A article, we will address some of the most frequently asked questions related to integrating a PSHOLD GPIO power-off mechanism on i.MX93 while retaining PSCI functionality.

Q1: What is the purpose of the PSHOLD GPIO power-off mechanism?

A1: The PSHOLD GPIO power-off mechanism is used to toggle a dedicated PSHOLD GPIO pin to completely cut power to the system during shutdown. This mechanism is essential for our board design, as it allows us to completely cut power to the system during shutdown.

Q2: How do I configure the PSCI interface to support the GPIO power-off mechanism?

A2: To configure the PSCI interface to support the GPIO power-off mechanism, you need to modify the PSCI interface to include the GPIO power-off mechanism configuration. This involves adding the gpio-poweroff node to the PSCI interface and configuring the GPIO power-off mechanism.

&soc {
    psci {
        compatible = "arm,psci-1.1";
        reg = <0x02000000 0x1000>;
        interrupts = <GIC_SPI 0 IRQ_TYPE_LEVEL_HIGH>;
        interrupt-parent = <&gic>;
        interrupt-names = "psci";
        gpio-poweroff {
            compatible = "gpio-poweroff";
            reg = <PHOLD_GPIO>;
            gpio-hog;
            gpio-ranges = <&pshold-gpio 0 1>;
        };
    };
};

Q3: How do I define the shutdown sequence to toggle the PSHOLD GPIO pin?

A3: To define the shutdown sequence to toggle the PSHOLD GPIO pin, you need to create a custom shutdown script that toggles the PSHOLD GPIO pin during shutdown. This involves exporting the PSHOLD GPIO pin, setting its direction to output, and writing the value to toggle the pin.

#!/bin/sh

echo "PHOLD_GPIO" > /sys/class/gpio/export echo "out" > /sys/class/gpio/gpioPHOLD_GPIO/direction echo "1" > /sys/class/gpio/gpioPHOLD_GPIO/value

Q4: How do I troubleshoot issues related to the PSHOLD GPIO power-off mechanism?

A4: To troubleshoot issues related to the PSHOLD GPIO power-off mechanism, you need to check the PSCI interface and the GPIO power-off mechanism configuration to ensure that they are not conflicting with each other. You also need to verify that the power management unit (PMU) is properly configured to support the GPIO power-off mechanism.

Q5: What are the benefits of integrating a PSHOLD GPIO power-off mechanism on i.MX93 while retaining PSCI functionality?

A5: The benefits of integrating a PSHOLD GPIO power-off mechanism on i.MX93 while retaining PSCI functionality include:

Improved power management: The PSHOLD GPIO power-off mechanism allows us to completely cut power to the system during shutdown, which improves power management and reduces power consumption.
Enhanced system reliability: The PSHOLD GPIO power-off mechanism ensures that the system is properly shut down, which enhances system reliability and reduces the risk of data corruption or system crashes.
Increased flexibility: The PSHOLD GPIO power-off mechanism provides a flexible way to control the power supply to the system, which allows us to customize the system's power management behavior.

Conclusion

In this Q&A article, we addressed some of the most frequently asked questions related to integrating a PSHOLD GPIO power-off mechanism on i.MX93 while retaining PSCI functionality. By following the step-by-step guide and troubleshooting tips outlined in this article, we can ensure that the PSHOLD GPIO power-off mechanism is properly integrated on i.MX93 while retaining PSCI functionality.