Linux/AM5748: Setting GPIO debouncing from user space

Christian Leeb

Part Number: AM5748

Tool/software: Linux

Hi,

For the GPIO controllers of AM5748x I'd like to know how to set debounce time from user space (e.g. by sys file system) or from device tree:

- How to set the debounce time per GPIO controller

- How to set the debounce clock: in device tree or user space?

Thanks, Chris

over 7 years ago

0 Cvetolin Shulev-XID over 7 years ago

TI__Guru 65405 points

Hi Christian,

Linux kernel gpio-keys devicetree documentation describes how to configure debounce-interval. Default value is 5 milliseconds.
www.kernel.org/.../gpio-keys.txt
www.kernel.org/.../gpio-keys-polled.txt
Also you can refer to linked below E2E thread for example configuration:
e2e.ti.com/.../580424

BR
Tsvetolin Shulev

0 Christian Leeb over 7 years ago in reply to Cvetolin Shulev-XID

Expert 1690 points

Thanks, Tsvetolin.

I checked the corresponding driver and found that this is actually software debouncing.

I would like to know how the GPIO controller assisted (hardware) debouncing is configured from user space or device tree.

See example for registers of AM574x (from AM574x TRM):

Thanks, Chris

0 Cvetolin Shulev-XID over 7 years ago in reply to Christian Leeb

TI__Guru 65405 points

Chris,

I'm sorry for the delayed response.
You can write GPIO_DEBOUNCINGTIME register directly in userspace but it is not recommended.
Kernel documentation gives an example about debounce-interval setting via device tree at:
www.kernel.org/.../gpio-keys.txt
.....
debounce-interval = <10>
.....
Also there is useful description in comments of ..<Linux-kernel>/drivers/gpio/gpio-omap.c driver.

Regards,
Tsvetolin Shulev

0 Christian Leeb over 7 years ago in reply to Cvetolin Shulev-XID

Expert 1690 points

Thanks, you can close the issue.

FYI:

setting GPIO_DEBOUNCINGTIME register is HW debouncing.

using gpio keys driver is SW debouncing.

Regards, Chris

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Linux/AM5748: Setting GPIO debouncing from user space