linux-kernel - Re: [PATCH 5/5] iio: addac: ad74413r: add support for reset-gpio

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Message-ID: <27be5a5bf23fbea31d82cf2e7b3f9747d7c610eb.camel@gmail.com>
Date:   Tue, 15 Nov 2022 15:53:06 +0100
From:   Nuno Sá <noname.nuno@...il.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Cosmin Tanislav <cosmin.tanislav@...log.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Jonathan Cameron <jic23@...nel.org>
Cc:     devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] iio: addac: ad74413r: add support for reset-gpio

On Fri, 2022-11-11 at 15:39 +0100, Rasmus Villemoes wrote:
> We have a board where the reset pin of the ad74412 is connected to a
> gpio, but also pulled low by default. Hence to get the chip out of
> reset, the driver needs to know about that gpio and set it high
> before
> attempting to communicate with it.
> 
> When a reset-gpio is given in device tree, use that instead of the
> software reset. According to the data sheet, the two methods are
> functionally equivalent.
> 
> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> ---
>  drivers/iio/addac/ad74413r.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/iio/addac/ad74413r.c
> b/drivers/iio/addac/ad74413r.c
> index 9f77d2f514de..af09d43f921c 100644
> --- a/drivers/iio/addac/ad74413r.c
> +++ b/drivers/iio/addac/ad74413r.c
> @@ -71,6 +71,7 @@ struct ad74413r_state {
>         struct regmap                   *regmap;
>         struct device                   *dev;
>         struct iio_trigger              *trig;
> +       struct gpio_desc                *reset_gpio;
>  
>         size_t                  adc_active_channels;
>         struct spi_message      adc_samples_msg;
> @@ -393,6 +394,13 @@ static int ad74413r_reset(struct ad74413r_state
> *st)
>  {
>         int ret;
>  
> +       if (st->reset_gpio) {
> +               gpiod_set_value_cansleep(st->reset_gpio, 1);
> +               fsleep(50);
> +               gpiod_set_value_cansleep(st->reset_gpio, 0);
> +               return 0;
> +       }
> +
>         ret = regmap_write(st->regmap, AD74413R_REG_CMD_KEY,
>                            AD74413R_CMD_KEY_RESET1);
>         if (ret)
> @@ -1316,6 +1324,10 @@ static int ad74413r_probe(struct spi_device
> *spi)
>         if (IS_ERR(st->regmap))
>                 return PTR_ERR(st->regmap);
>  
> +       st->reset_gpio = devm_gpiod_get_optional(st->dev, "reset",
> GPIOD_OUT_LOW);
> +       if (IS_ERR(st->reset_gpio))
> +               return PTR_ERR(st->reset_gpio);
> +

Minor thing but,

I would move this into ad74413r_reset() as there's no real need to have
the gpio_desc in struct ad74413r_state.

- Nuno Sá