linux-kernel - Re: [PATCH v5 2/3] iio: adc: tsc2046: add vref support

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Date:   Sat, 3 Sep 2022 12:26:32 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>
Subject: Re: [PATCH v5 2/3] iio: adc: tsc2046: add vref support

On Sat, Sep 3, 2022 at 8:03 AM Oleksij Rempel <o.rempel@...gutronix.de> wrote:
>
> If VREF pin is attached, we should use external VREF source instead of
> the internal. Otherwise we will get wrong measurements on some of the channel
> types.

FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> ---
> changes v5:
> - add "the" before channel
> - refactor error handling on regulator registration
> - use MILLI instead of 1000
> changes v4:
> - use vref_reg pointer instead of bool use_internal_vref
> - move regulator registration to a separate function
> - rework error handling
> - add devm_add_action_or_reset
> ---
>  drivers/iio/adc/ti-tsc2046.c | 57 ++++++++++++++++++++++++++++++++++--
>  1 file changed, 55 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/adc/ti-tsc2046.c b/drivers/iio/adc/ti-tsc2046.c
> index 0d9436a69cbfb..c7601b29b3bef 100644
> --- a/drivers/iio/adc/ti-tsc2046.c
> +++ b/drivers/iio/adc/ti-tsc2046.c
> @@ -8,7 +8,9 @@
>  #include <linux/bitfield.h>
>  #include <linux/delay.h>
>  #include <linux/module.h>
> +#include <linux/regulator/consumer.h>
>  #include <linux/spi/spi.h>
> +#include <linux/units.h>
>
>  #include <asm/unaligned.h>
>
> @@ -175,6 +177,8 @@ struct tsc2046_adc_priv {
>         u32 time_per_bit_ns;
>
>         struct tsc2046_adc_ch_cfg ch_cfg[TI_TSC2046_MAX_CHAN];
> +       unsigned int vref_mv;
> +       struct regulator *vref_reg;

I would put pointer first since it will make sizeof(priv) 4 bytes less
on some architectures due to padding elimination.

>  };
>
>  #define TI_TSC2046_V_CHAN(index, bits, name)                   \
> @@ -252,7 +256,9 @@ static u8 tsc2046_adc_get_cmd(struct tsc2046_adc_priv *priv, int ch_idx,
>         case TI_TSC2046_ADDR_AUX:
>         case TI_TSC2046_ADDR_VBAT:
>         case TI_TSC2046_ADDR_TEMP0:
> -               pd |= TI_TSC2046_SER | TI_TSC2046_PD1_VREF_ON;
> +               pd |= TI_TSC2046_SER;
> +               if (!priv->vref_reg)
> +                       pd |= TI_TSC2046_PD1_VREF_ON;
>         }
>
>         return TI_TSC2046_START | FIELD_PREP(TI_TSC2046_ADDR, ch_idx) | pd;
> @@ -468,7 +474,7 @@ static int tsc2046_adc_read_raw(struct iio_dev *indio_dev,
>                  * So, it is better to use external voltage-divider driver
>                  * instead, which is calculating complete chain.
>                  */
> -               *val = TI_TSC2046_INT_VREF;
> +               *val = priv->vref_mv;
>                 *val2 = chan->scan_type.realbits;
>                 return IIO_VAL_FRACTIONAL_LOG2;
>         }
> @@ -740,6 +746,49 @@ static void tsc2046_adc_parse_fwnode(struct tsc2046_adc_priv *priv)
>         }
>  }
>
> +static void tsc2046_adc_regulator_disable(void *data)
> +{
> +       struct tsc2046_adc_priv *priv = data;
> +
> +       regulator_disable(priv->vref_reg);
> +}
> +
> +static int tsc2046_adc_configure_regulator(struct tsc2046_adc_priv *priv)
> +{
> +       struct device *dev = &priv->spi->dev;
> +       int ret;
> +
> +       priv->vref_reg = devm_regulator_get_optional(dev, "vref");
> +       if (IS_ERR(priv->vref_reg)) {
> +               /* If regulator exists but can't be get, return an error */
> +               if (PTR_ERR(priv->vref_reg) != -ENODEV)
> +                       return PTR_ERR(priv->vref_reg);
> +               priv->vref_reg = NULL;
> +       }
> +       if (!priv->vref_reg) {
> +               /* Use internal reference */
> +               priv->vref_mv = TI_TSC2046_INT_VREF;
> +               return 0;
> +       }
> +
> +       ret = regulator_enable(priv->vref_reg);
> +       if (ret)
> +               return ret;
> +
> +       ret = devm_add_action_or_reset(dev, tsc2046_adc_regulator_disable,
> +                                      priv);
> +       if (ret)
> +               return ret;
> +
> +       ret = regulator_get_voltage(priv->vref_reg);
> +       if (ret < 0)
> +               return ret;
> +
> +       priv->vref_mv = ret / MILLI;
> +
> +       return 0;
> +}
> +
>  static int tsc2046_adc_probe(struct spi_device *spi)
>  {
>         const struct tsc2046_adc_dcfg *dcfg;
> @@ -781,6 +830,10 @@ static int tsc2046_adc_probe(struct spi_device *spi)
>         indio_dev->num_channels = dcfg->num_channels;
>         indio_dev->info = &tsc2046_adc_info;
>
> +       ret = tsc2046_adc_configure_regulator(priv);
> +       if (ret)
> +               return ret;
> +
>         tsc2046_adc_parse_fwnode(priv);
>
>         ret = tsc2046_adc_setup_spi_msg(priv);
> --
> 2.30.2
>


-- 
With Best Regards,
Andy Shevchenko