AM625: AM625 GPIO not accessible in custom kernel character driver

Vijay Gawade

Prodigy 60 points

Part Number: AM625

Tool/software:

Hi Team,

I'm trying to write custom kernel character driver buzzer with some additional tones.

I have implemented following changes:

Define pin as GPIO1_10 (E18) in device tree
Define node with above pins and set status as "okay"
write custom character driver as a Linux Loadable Kernel Module (LKM) at "drivers/misc/tfs_buzzer.c" to access same gpio using gpio_request API

AM62 DataSheet:- https://www.variscite.com/wp-content/uploads/2023/01/VAR-SOM-AM62_Datasheet.pdf

Base Image:- https://variwiki.com/index.php?title=Yocto_Build_Release&release=am62-yocto-kirkstone-6.1.83_09.02.01.10-v1.1

arch/arm64/boot/dts/ti/k3-am625-var-som-symphony.dts

/ {

    /*  Buzzer Enable */

    tfs_buzzer_enable_gpio: tfs-buzzer-enable-gpio {

        label = "BuzzerEnable";

        linux,default-trigger = "default-on";

        gpios = <&main_gpio0 22 GPIO_ACTIVE_HIGH>;

        status = "okay";

    };

 

    /*  Buzzer Tone */

    tfs_buzzer_tone_gpio: tfs-buzzer-tone-gpio {

        label = "BuzzerTone";

        linux,default-trigger = "default-on";

        gpios = <&main_gpio1 10 GPIO_ACTIVE_HIGH>;

        status = "okay";

    };

};

 

main_pmx0 {

    status = "okay";

    pinctrl-names = "default";

    pinctrl-0 = <&display_pins_default>;

 

    display_pins_default: display-default-pins {

        pinctrl-single,pins = <

            /* Buzzer Pins */

            AM62X_IOPAD(0x0058, PIN_OUTPUT_PULLUP, 7) /* (R23) GPMC0_AD7.GPIO0_22 */

            AM62X_IOPAD(0x01a0, PIN_OUTPUT_PULLUP, 7) /* (E18) MCASP0_AXR0.GPIO1_10 */

         >;

    };

};

drivers/misc/tfs_buzzer.c

static int buzzer_gpio_init(void)

{

    int ret = -1;

    int gpio_num = 378;

 

    ret = gpio_request(gpio_num, "BUZZER_GPIO");

    if (ret) {

        if (ret == -EPROBE_DEFER) {

            pr_info("GPIO %d request deferred, retrying later\n", gpio_num);

        } else {

            pr_err("Failed to request GPIO %d for BUZZER_GPIO: %d\n", gpio_num, ret);

        }

        return ret;

    } else {

        gpio_direction_output(gpio_num, 1);

        gpio_set_value(gpio_num, 1); // default buzzer is disabled

        buzzer_dev->status = BUZZER_DISABLE;

    }

 

    return 0;

}

Driver Error:

gpio_request() returns code -517 corresponds to -EPROBE_DEFER. This error code indicates that the GPIO request is being deferred because a required resource is not yet available

GPIO_Info

over 1 year ago

0 Anshu Madwesh over 1 year ago

TI__Mastermind 24525 points

Hello,

There is very limited support for custom drivers and applications because its beyond the scope of the E2E forums. We can only provide support for code provided in the Linux SDK because its been tested and validated by TI.

With that said, there are a few things that can be checked:

1. Make sure the GPIO works normally in userspace.

Try something basic like this:

&main_pmx0 {
	main_gpio1_pins_default: main-gpio1-default-pins {
		pinctrl-single,pins = <
			AM62X_IOPAD(0x01a0, PIN_INPUT, 7) /* (E18) MCASP0_AXR0.GPIO1_10 */
		>;
	};
};

&main_gpio1 {
    status = "okay";
    pinctrl-names = "default";
    pinctrl-0 = <&main_gpio1_pins_default>;
};

Use this along with GPIO userspace commands to set the GPIO high/low to test it works.

2. From the device tree, linux,default-trigger is typically used for LED applications and GPIOs calling a specific driver will typically state the compatible string. This may not apply in this case because I don't know how you driver works. Refer to the LED on a TI EVM as an example: https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi?h=ti-linux-6.6.y#n116

3. cat /sys/kernel/debug/gpio may have some useful information.

4. Refer to the legacy API for GPIOs: https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/Documentation/driver-api/gpio/legacy.rst?h=ti-linux-6.6.y

Again, there is very limited support that TI can provide for custom applications.

Best Regards,

Anshu

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AM625: AM625 GPIO not accessible in custom kernel character driver