Re: [PATCH] gpio: sifive: use the correct register to read output values

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Sat, Feb 5, 2022 at 12:33 AM Damien Le Moal
<damien.lemoal@xxxxxxxxxxxxxxxxxx> wrote:
>
> On 2/4/22 22:02, Niklas Cassel wrote:
> > From: Niklas Cassel <niklas.cassel@xxxxxxx>
> >
> > Setting the output of a GPIO to 1 using gpiod_set_value(), followed by
> > reading the same GPIO using gpiod_get_value(), will currently yield an
> > incorrect result.
> >
> > This is because the SiFive GPIO device stores the output values in reg_set,
> > not reg_dat.
> >
> > Supply the flag BGPIOF_READ_OUTPUT_REG_SET to bgpio_init() so that the
> > generic driver reads the correct register.
> >
> > Signed-off-by: Niklas Cassel <niklas.cassel@xxxxxxx>
>
> This probably needs a Fixes tag. I have not checked which patch though.
>

I added the tag and queued this for fixes, thanks!

Bart

> > ---
> > The patch was tested on a canaan,k210 board (canaan,k210-gpiohs compatible
> > string). It would be nice with a Tested-by from someone with a SiFive board.
> >
> > However, the u-boot driver for this device already behaves exactly the same
> > as this driver does after my patch, for all platforms using the driver.
> >
> >  drivers/gpio/gpio-sifive.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpio/gpio-sifive.c b/drivers/gpio/gpio-sifive.c
> > index 403f9e833d6a..7d82388b4ab7 100644
> > --- a/drivers/gpio/gpio-sifive.c
> > +++ b/drivers/gpio/gpio-sifive.c
> > @@ -223,7 +223,7 @@ static int sifive_gpio_probe(struct platform_device *pdev)
> >                        NULL,
> >                        chip->base + SIFIVE_GPIO_OUTPUT_EN,
> >                        chip->base + SIFIVE_GPIO_INPUT_EN,
> > -                      0);
> > +                      BGPIOF_READ_OUTPUT_REG_SET);
> >       if (ret) {
> >               dev_err(dev, "unable to init generic GPIO\n");
> >               return ret;
>
>
> --
> Damien Le Moal
> Western Digital Research