Re: [PATCH v3 2/5] iio: ad7949: Support internal Vref

[Alexandru Ardelean <ardeleanalex@gmail.com>]

On Mon, May 13, 2019 at 7:16 PM Adam Michaelis
<adam.michaelis@rockwellcollins.com> wrote:
>
> Adding configurable (via device tree) options to select one of the two
> external reference voltages (REFIN as default, original implementation)
> or one of the two internal reference voltages provided by the AD7949
> part family.
>

I would run a ./scripts/checkpatch.pl on this patch (maybe also on the series).
I would only complain about style-stuff (on this patch), but those
would also get reported by checkpatch.

> Signed-off-by: Adam Michaelis <adam.michaelis@rockwellcollins.com>
> ---
>         V2:
>         - Add some defines to reduce use of magic numbers.
>         V3:
>         - Add bitfield.h macros throughout.
>         - Re-think usage of device tree parameter to focus on the
>         actual reference sources instead of the raw hardware
>         configuration.
> ---
>  drivers/iio/adc/ad7949.c | 138 +++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 111 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
> index c7fe27aa2519..b648b1ab9559 100644
> --- a/drivers/iio/adc/ad7949.c
> +++ b/drivers/iio/adc/ad7949.c
> @@ -11,12 +11,23 @@
>  #include <linux/module.h>
>  #include <linux/regulator/consumer.h>
>  #include <linux/spi/spi.h>
> -
> -#define AD7949_MASK_CHANNEL_SEL                GENMASK(9, 7)
> -#define AD7949_MASK_TOTAL              GENMASK(13, 0)
> -#define AD7949_OFFSET_CHANNEL_SEL      7
> -#define AD7949_CFG_READ_BACK           0x1
> -#define AD7949_CFG_REG_SIZE_BITS       14
> +#include <linux/of.h>
> +#include <linux/bitfield.h>
> +
> +#define AD7949_CFG_REG_SIZE_BITS           14
> +#define AD7949_CFG_MASK_TOTAL              GENMASK(13, 0)
> +#define AD7949_CFG_APPLY                   BIT(13)
> +#define AD7949_CFG_CHAN_CFG                GENMASK(12, 10)
> +#define AD7949_CFG_CHAN_CFG_UNIPOLAR_GND   0x7
> +#define AD7949_CFG_CHAN_SEL                GENMASK(9, 7)
> +#define AD7949_CFG_BW                      BIT(6)
> +#define AD7949_CFG_BW_FULL                 1
> +#define AD7949_CFG_REF_SEL                 GENMASK(5, 3)
> +#define AD7949_CFG_SEQ                     GENMASK(2, 1)
> +#define AD7949_CFG_SEQ_DISABLED            0x0
> +#define AD7949_CFG_READBACK                BIT(0)
> +#define AD7949_CFG_READBACK_EN             0
> +#define AD7949_CFG_READBACK_DIS            1
>
>  enum {
>         ID_AD7949 = 0,
> @@ -24,6 +35,18 @@ enum {
>         ID_AD7689,
>  };
>
> +enum ad7949_ref_sel {
> +       AD7949_REF_2V5 = 0, /* 2.5V internal ref + temp sensor */
> +       AD7949_REF_4V0, /* 4.096V internal ref + temp sensor */
> +       AD7949_REF_EXT_TEMP, /* REF + temp sensor */
> +       AD7949_REF_EXT_TEMP_BUF, /* REFIN + temp sensor */
> +       AD7949_REF_RSRV_4,
> +       AD7949_REF_RSRV_5,
> +       AD7949_REF_EXT, /* REF, no temp */
> +       AD7949_REF_EXT_BUF, /* REFIN, no temp */
> +       AD7949_REF_MAX,
> +};
> +
>  struct ad7949_adc_spec {
>         u8 num_channels;
>         u8 resolution;
> @@ -41,6 +64,7 @@ struct ad7949_adc_spec {
>   * @vref: regulator generating Vref
>   * @iio_dev: reference to iio structure
>   * @spi: reference to spi structure
> + * @ref_sel: selected reference voltage source
>   * @resolution: resolution of the chip
>   * @cfg: copy of the configuration register
>   * @current_channel: current channel in use
> @@ -51,6 +75,7 @@ struct ad7949_adc_chip {
>         struct regulator *vref;
>         struct iio_dev *indio_dev;
>         struct spi_device *spi;
> +       enum ad7949_ref_sel ref_sel;
>         u8 resolution;
>         u16 cfg;
>         unsigned int current_channel;
> @@ -59,7 +84,7 @@ struct ad7949_adc_chip {
>
>  static bool ad7949_spi_cfg_is_read_back(struct ad7949_adc_chip *ad7949_adc)
>  {
> -       if (!(ad7949_adc->cfg & AD7949_CFG_READ_BACK))
> +       if (!(ad7949_adc->cfg & AD7949_CFG_READBACK))
>                 return true;
>
>         return false;
> @@ -91,7 +116,7 @@ static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val,
>         };
>
>         ad7949_adc->cfg = (val & mask) | (ad7949_adc->cfg & ~mask);
> -       ad7949_adc->buffer = ad7949_adc->cfg << shift;
> +       ad7949_adc->buffer = (ad7949_adc->cfg & AD7949_CFG_MASK_TOTAL) << shift;
>         spi_message_init_with_transfers(&msg, tx, 1);
>         ret = spi_sync(ad7949_adc->spi, &msg);
>
> @@ -136,8 +161,8 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
>         };
>
>         ret = ad7949_spi_write_cfg(ad7949_adc,
> -                                  channel << AD7949_OFFSET_CHANNEL_SEL,
> -                                  AD7949_MASK_CHANNEL_SEL);
> +                                  FIELD_PREP(AD7949_CFG_CHAN_SEL, channel),
> +                                  AD7949_CFG_CHAN_SEL);
>         if (ret)
>                 return ret;
>
> @@ -204,11 +229,20 @@ static int ad7949_spi_read_raw(struct iio_dev *indio_dev,
>                 return IIO_VAL_INT;
>
>         case IIO_CHAN_INFO_SCALE:
> -               ret = regulator_get_voltage(ad7949_adc->vref);
> -               if (ret < 0)
> -                       return ret;
> +               if (ad7949_adc->vref) {
> +                       ret = regulator_get_voltage(ad7949_adc->vref);
> +                       if (ret < 0)
> +                               return ret;
> +
> +                       *val = ret / 5000;
> +               } else if (ad7949_adc->ref_sel == AD7949_REF_2V5) {
> +                       *val = 2500;
> +               } else if (ad7949_adc->ref_sel == AD7949_REF_4V0) {
> +                       *val = 4096;
> +               } else {
> +                       return -EINVAL;
> +               }
>
> -               *val = ret / 5000;
>                 return IIO_VAL_INT;
>         }
>
> @@ -226,7 +260,8 @@ static int ad7949_spi_reg_access(struct iio_dev *indio_dev,
>                 *readval = ad7949_adc->cfg;
>         else
>                 ret = ad7949_spi_write_cfg(ad7949_adc,
> -                       writeval & AD7949_MASK_TOTAL, AD7949_MASK_TOTAL);
> +                       writeval & AD7949_CFG_MASK_TOTAL,
> +                       AD7949_CFG_MASK_TOTAL);
>
>         return ret;
>  }
> @@ -240,10 +275,24 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
>  {
>         int ret;
>         int val;
> +       u16 adc_config = 0;
>
> -       /* Sequencer disabled, CFG readback disabled, IN0 as default channel */
>         ad7949_adc->current_channel = 0;
> -       ret = ad7949_spi_write_cfg(ad7949_adc, 0x3C79, AD7949_MASK_TOTAL);
> +       ad7949_adc->cfg = 0;
> +
> +       adc_config |= FIELD_PREP(AD7949_CFG_APPLY, 1);
> +       adc_config |= FIELD_PREP(AD7949_CFG_CHAN_CFG,
> +                       AD7949_CFG_CHAN_CFG_UNIPOLAR_GND);
> +       adc_config |= FIELD_PREP(AD7949_CFG_CHAN_SEL,
> +                       ad7949_adc->current_channel);
> +       adc_config |= FIELD_PREP(AD7949_CFG_BW, AD7949_CFG_BW_FULL);
> +       adc_config |= FIELD_PREP(AD7949_CFG_REF_SEL, ad7949_adc->ref_sel);
> +       adc_config |= FIELD_PREP(AD7949_CFG_SEQ, AD7949_CFG_SEQ_DISABLED);
> +       adc_config |= FIELD_PREP(AD7949_CFG_READBACK, AD7949_CFG_READBACK_DIS);
> +
> +       ret = ad7949_spi_write_cfg(ad7949_adc,
> +                       adc_config,
> +                       AD7949_CFG_MASK_TOTAL);
>
>         /*
>          * Do a dummy conversion to apply the first configuration setting.
> @@ -261,6 +310,7 @@ static int ad7949_spi_probe(struct spi_device *spi)
>         struct ad7949_adc_chip *ad7949_adc;
>         struct iio_dev *indio_dev;
>         int ret;
> +       u32 temp;
>
>         indio_dev = devm_iio_device_alloc(dev, sizeof(*ad7949_adc));
>         if (!indio_dev) {
> @@ -279,21 +329,53 @@ static int ad7949_spi_probe(struct spi_device *spi)
>         ad7949_adc = iio_priv(indio_dev);
>         ad7949_adc->indio_dev = indio_dev;
>         ad7949_adc->spi = spi;
> +       ad7949_adc->vref = NULL;
>
>         spec = &ad7949_adc_spec[spi_get_device_id(spi)->driver_data];
>         indio_dev->num_channels = spec->num_channels;
>         ad7949_adc->resolution = spec->resolution;
>
> -       ad7949_adc->vref = devm_regulator_get(dev, "vref");
> -       if (IS_ERR(ad7949_adc->vref)) {
> -               dev_err(dev, "fail to request regulator\n");
> -               return PTR_ERR(ad7949_adc->vref);
> +       ret = of_property_read_u32(ad7949_adc->indio_dev->dev.of_node,
> +                       "adi,reference-select",
> +                       &temp);
> +       if (ret == 0) {
> +               switch (temp) {
> +               case 0:
> +                       ad7949_adc->ref_sel = AD7949_REF_2V5;
> +                       break;
> +               case 1:
> +                       ad7949_adc->ref_sel = AD7949_REF_4V0;
> +                       break;
> +               case 2:
> +                       ad7949_adc->ref_sel = AD7949_REF_EXT;
> +                       break;
> +               case 3:
> +                       ad7949_adc->ref_sel = AD7949_REF_EXT_BUF;
> +                       break;
> +               default:
> +                       ad7949_adc->ref_sel = AD7949_REF_EXT_BUF;
> +                       dev_warn(dev,
> +                               "unknown reference-select value, using REFIN external Vref (3) by default\n");
> +               }
> +       } else {
> +               ad7949_adc->ref_sel = AD7949_REF_EXT_BUF;
> +               dev_warn(dev, "using external Vref by default\n");
>         }
>
> -       ret = regulator_enable(ad7949_adc->vref);
> -       if (ret < 0) {
> -               dev_err(dev, "fail to enable regulator\n");
> -               return ret;
> +       /* Check whether using external Vref */
> +       if ((ad7949_adc->ref_sel != AD7949_REF_2V5) &&
> +                       (ad7949_adc->ref_sel != AD7949_REF_4V0)) {
> +               ad7949_adc->vref = devm_regulator_get(dev, "vref");
> +               if (IS_ERR(ad7949_adc->vref)) {
> +                       dev_err(dev, "fail to request regulator\n");
> +                       return PTR_ERR(ad7949_adc->vref);
> +               }
> +
> +               ret = regulator_enable(ad7949_adc->vref);
> +               if (ret < 0) {
> +                       dev_err(dev, "fail to enable regulator\n");
> +                       return ret;
> +               }
>         }
>
>         mutex_init(&ad7949_adc->lock);
> @@ -314,7 +396,8 @@ static int ad7949_spi_probe(struct spi_device *spi)
>
>  err:
>         mutex_destroy(&ad7949_adc->lock);
> -       regulator_disable(ad7949_adc->vref);
> +       if (ad7949_adc->vref)
> +               regulator_disable(ad7949_adc->vref);
>
>         return ret;
>  }
> @@ -326,7 +409,8 @@ static int ad7949_spi_remove(struct spi_device *spi)
>
>         iio_device_unregister(indio_dev);
>         mutex_destroy(&ad7949_adc->lock);
> -       regulator_disable(ad7949_adc->vref);
> +       if (ad7949_adc->vref)
> +               regulator_disable(ad7949_adc->vref);
>
>         return 0;
>  }
> --
> 1.9.1
>