AM6442: GPIO reset during reboot

Artur Toews

Prodigy 150 points

Part Number: AM6442

Tool/software:

Hallo,

is it possible to prevent a gpio pin to be resetted.

We configured a gpio as gpio-hog and set it high:

main_gpio0_pins_default: main-gpio0-pins-default {
...
	    AM64X_IOPAD(0x00d8, PIN_OUTPUT, 7) /* (W13) PRG1_PRU0_GPO8.GPIO0_53 */
...
}

&main_gpio0 {
	pinctrl-names = "default";
	pinctrl-0 = <&main_gpio0_pins_default>;
	
	    ...

		nReset {
			gpio-hog;
			gpios = <53 0>;
			output-high;
		};
};

This pin is set to low during reboot. But we would like to keep it high. Is it possible?

I checked already the gpio in u-boot, but it's not used there.

Regards,
Artur

4 months ago

0 Qutaiba Saleh 4 months ago

TI__Expert 4720 points

Hi Artur,

The expert on the matter is currently on a trip. Please, expect some delay in the response.

Best regards,

Qutaiba

0 Anshu Madwesh 3 months ago in reply to Qutaiba Saleh

TI__Mastermind 18380 points

Hi Artur,

During reboot, the hardware will be re-initialized which will cause state to be reset.

You can look into setting the GPIO in U-Boot:

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1523611/faq-processor-sdk-am62x-how-to-toggle-a-gpio-from-r5-spl

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1398803/faq-processor-sdk-am62x-how-to-toggle-gpios-and-leds-from-u-boot-command-prompt

Best Regards,

Anshu

0 Artur Toews 3 months ago in reply to Anshu Madwesh

Prodigy 150 points

Hi Anshu,

according to your answer, it sounds as if it is not possible to simply leave the pin untouched during a soft restart.
The SPL must also set the PIN to the desired level.

Let's assume we set the PIN in the SPL to high and in Linux too. Is the PIN then really NEVER set to low during the soft restart?

Best Regards,
Artur

0 Anshu Madwesh 3 months ago in reply to Artur Toews

TI__Mastermind 18380 points

Hi Artur,

I'm not sure if the GPIO register get overwritten when booting Linux and how gpio-hog may impact this. We can check one of the GPIO register at U-Boot command line using the mw/md.l commands and then again after Linux has booted using the devmem2.

Refer to the GPIO register section AM64 TRM: https://www.ti.com/lit/pdf/spruim2

Best Regards,

Anshu

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AM6442: GPIO reset during reboot