linux-kernel - Re: [PATCH v2 1/1] gpio: mpc8xxx: latch GPIOs state on module load when configured as output

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Date:   Fri, 16 Jun 2023 11:11:40 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     msmulski2@...il.com
Cc:     linus.walleij@...aro.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Michal Smulski <michal.smulski@...a.com>
Subject: Re: [PATCH v2 1/1] gpio: mpc8xxx: latch GPIOs state on module load
 when configured as output

On Fri, Jun 2, 2023 at 1:02 AM <msmulski2@...il.com> wrote:
>
> From: Michal Smulski <michal.smulski@...a.com>
>
> Qoriq and related devices allow reading out state of GPIO set as output.
> However, currently on driver's init, all outputs are configured as driven
> low. So, any changes to GPIO confiuration will drive all pins (configured
> as output) as output-low.
> This patch latches state of output GPIOs before any GPIO configuration
> takes place. This preserves any output settings done prior to loading
> the driver (for example, by u-boot).
>
> Signed-off-by: Michal Smulski <michal.smulski@...a.com>
> ---
>  drivers/gpio/gpio-mpc8xxx.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpio-mpc8xxx.c b/drivers/gpio/gpio-mpc8xxx.c
> index 3eb08cd1fdc0..6340e738c912 100644
> --- a/drivers/gpio/gpio-mpc8xxx.c
> +++ b/drivers/gpio/gpio-mpc8xxx.c
> @@ -375,8 +375,12 @@ static int mpc8xxx_probe(struct platform_device *pdev)
>         if (of_device_is_compatible(np, "fsl,qoriq-gpio") ||
>             of_device_is_compatible(np, "fsl,ls1028a-gpio") ||
>             of_device_is_compatible(np, "fsl,ls1088a-gpio") ||
> -           is_acpi_node(fwnode))
> +           is_acpi_node(fwnode)) {
>                 gc->write_reg(mpc8xxx_gc->regs + GPIO_IBE, 0xffffffff);
> +               /* Also, latch state of GPIOs configured as output by bootloader. */
> +               gc->bgpio_data = gc->read_reg(mpc8xxx_gc->regs + GPIO_DAT) &
> +                       gc->read_reg(mpc8xxx_gc->regs + GPIO_DIR);
> +       }
>
>         ret = devm_gpiochip_add_data(&pdev->dev, gc, mpc8xxx_gc);
>         if (ret) {
> --
> 2.34.1
>

Applied, thanks!

Bart