Verdin imx8mp: CTRL_SLEEP_MOCI remains high during sleep mode

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Hello Loris,

Thank you for your detailed description.

The desired CTRL_SLEEP_MOCI# behavior (high when the SoM is running, low in sleep) is supported as of BSP 6.4+. Since you are using a recent kernel and the Scarthgap Yocto (BSP 7.x.y), you should be able to achieve this, but a few critical points should be adjusted in your device tree.

Main Factors for CTRL_SLEEP_MOCI# Operation

  1. GPIO Polarity:
    CTRL_SLEEP_MOCI# (note the #) means “active low.” The SoM asserts this pin low in sleep mode.
    • The physical behavior: High in run, Low (asserted) in sleep
  2. Device Tree Regulator Configuration:
    You want the regulator to be disabled (output low) during system suspend and enabled (output high) during normal operation.
  3. Pinmux and GPIO Configuration:
    The pin must remain configured as output and under kernel control for sleep transitions.

1. Regulator Configuration

Current State:

You are using

enable-active-high;
gpio = <&gpio4 29 GPIO_ACTIVE_HIGH>;
regulator-always-on;
regulator-boot-on;
  • regulator-always-on keeps the regulator always ON; it will never go off in suspend.

Fix:

Remove regulator-always-on and (optionally) regulator-boot-on.

  • DO NOT set regulator-always-on if you want the pin to drop in suspend.

Use this:

reg_force_sleep_moci: regulator-force-sleep-moci {
    compatible = "regulator-fixed";
    enable-active-high;
    /* Verdin CTRL_SLEEP_MOCI# (SODIMM 256) */
    gpio = <&gpio4 29 GPIO_ACTIVE_HIGH>;
    regulator-name = "CTRL_SLEEP_MOCI#";
    /* regulator-always-on; <-- REMOVE THIS */
    /* regulator-boot-on;   <-- REMOVE THIS */
};

This way, the driver is allowed to disable the GPIO (= assert low) during suspend.

2. Pinmux

Your pinmux is correct, just ensure nothing else overrides this pin.

pinctrl_ctrl_sleep_moci: ctrlsleepmocigrp {
    fsl,pins =
        <MX8MP_IOMUXC_SAI3_RXC__GPIO4_IO29 0x1c4>; /* SODIMM 256 */
};

3. Regulator Consumers

The proper functioning depends on something marking the regulator as required only during normal operation, and letting the kernel disable it during suspend.

Example:

  • Ensure any device in the device tree that “uses” this supply lists regulator-force-sleep-moci as its supply.
    &i2c1 {
    vcc-supply = <&reg_force_sleep_moci>;
    /* ... */
};
  • Or, if you don’t want to control a specific device, you can use the default configuration and the kernel should disable unneeded regulators in suspend.

4. Kernel Power Management

The kernel’s power management must be enabled and SoM must actually suspend for the pin to change.

  • Use echo mem > /sys/power/state to test sleep.
  • The CTRL_SLEEP_MOCI# pin should go low when suspended and return high when resumed.

Summary of Your Required Device Tree Changes

  1. Remove regulator-always-on; and regulator-boot-on; from reg_force_sleep_moci.
  2. Ensure the gpio line is correct and pinmux is configured as output.
  3. Make sure any critical peripherals on your carrier depend on reg_force_sleep_moci.
  4. Confirm sleep state is working (i.e., SoM actually enters suspend).

Useful Links

Would you like a complete example device tree overlay or more details on how to test the state change in Linux?

Best regards,
Toradex AI Assistant.