linux-kernel - Re: Using Pull-up resistors on gpio-pca953x expander

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Message-ID: <CACRpkdayE023wfdJxHDVNtSF08kqGG6kfW7vkZhnq7OpcnmuEg@mail.gmail.com>
Date:   Thu, 16 Jan 2020 10:42:08 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Adam Ford <aford173@...il.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: Using Pull-up resistors on gpio-pca953x expander

On Wed, Jan 15, 2020 at 9:26 PM Adam Ford <aford173@...il.com> wrote:

> The pca953x can support pull-up resistors, and I have a pcal6416 that
> I'd like to enable them.

OK this is supported in the driver since
commit 15add06841a3b0b4734a72847a73c71fd09ebe52
"gpio: pca953x: add ->set_config implementation"

> Ideally, I was hoping there would be a way to add enable to the device
> tree, because the expander is connected to some buttons which are
> grounded when pressed.  Without pull-up resistors enabled, the buttons
> always appear to be pressed.
>
> Is there some way to enable them?  I see the functionality is
> available and called through gc->set_config = pca953x_gpio_set_config;
(...)
> Would you entertain my adding some device tree hooks to enable them?

Have you tried something like this in your DTS:

#include <dt-bindings/gpio/gpio.h>
(...)
gpios = <&gpio 4 (GPIO_ACTIVE_LOW | GPIO_PULL_UP)>;

Yours,
Linus Walleij