Re: [PATCH v2 1/2] staging: iio: ad7780: add gain & filter gpio support

["Popa, Stefan Serban" <StefanSerban.Popa@analog.com>]

On Du, 2019-01-27 at 18:30 -0200, Renato Lui Geh wrote:
> Previously, the AD7780 driver only supported gpio for the 'powerdown'
> pin. This commit adds suppport for the 'gain' and 'filter' pin.
> 
> Signed-off-by: Renato Lui Geh <renatogeh@gmail.com>
> Signed-off-by: Giuliano Belinassi <giuliano.belinassi@usp.br>
> Co-developed-by: Giuliano Belinassi <giuliano.belinassi@usp.br>
> ---
> Changes in v2:
>         - Filter reading changed to mHz
>         - Storing filter, gain and voltage to chip_info

Hi,

Comments inline.

Regards,
Stefan

> 
>  drivers/staging/iio/adc/ad7780.c       | 103 ++++++++++++++++++++++---
>  include/linux/iio/adc/ad_sigma_delta.h |   5 ++
>  2 files changed, 99 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/staging/iio/adc/ad7780.c
> b/drivers/staging/iio/adc/ad7780.c
> index c4a85789c2db..82394e31b168 100644
> --- a/drivers/staging/iio/adc/ad7780.c
> +++ b/drivers/staging/iio/adc/ad7780.c
> @@ -39,6 +39,15 @@
>  #define AD7170_PATTERN         (AD7780_PAT0 | AD7170_PAT2)
>  #define AD7170_PATTERN_MASK    (AD7780_PAT0 | AD7780_PAT1 | AD7170_PAT2)
> 
> +#define AD7780_GAIN_GPIO       0
> +#define AD7780_FILTER_GPIO     1
> +
> +#define AD7780_GAIN_MIDPOINT   64
> +#define AD7780_FILTER_MIDPOINT 13350
> +
> +static const unsigned int ad778x_gain[2]    = { 1, 128 };
> +static const unsigned int ad778x_filter[2]  = { 10000, 16700 };
I would name this array ad778x_odr_avail or something like that. We should
also consider adding the option to read the available sampling frequencies
from user space, but let's leave this for another commit.
> +
>  struct ad7780_chip_info {
>         struct iio_chan_spec    channel;
>         unsigned int            pattern_mask;
> @@ -50,7 +59,11 @@ struct ad7780_state {
>         const struct ad7780_chip_info   *chip_info;
>         struct regulator                *reg;
>         struct gpio_desc                *powerdown_gpio;
> -       unsigned int    gain;
> +       struct gpio_desc                *gain_gpio;
> +       struct gpio_desc                *filter_gpio;
> +       unsigned int                    gain;
> +       unsigned int                    filter;

Also, this could be renamed as odr.

> +       unsigned int                    int_vref_mv;
> 
>         struct ad_sigma_delta sd;
>  };
> @@ -104,17 +117,65 @@ static int ad7780_read_raw(struct iio_dev
> *indio_dev,
>                 voltage_uv = regulator_get_voltage(st->reg);
>                 if (voltage_uv < 0)
>                         return voltage_uv;
> -               *val = (voltage_uv / 1000) * st->gain;
> +               voltage_uv /= 1000;
> +               *val = voltage_uv * st->gain;
>                 *val2 = chan->scan_type.realbits - 1;
> +               st->int_vref_mv = voltage_uv;
>                 return IIO_VAL_FRACTIONAL_LOG2;
>         case IIO_CHAN_INFO_OFFSET:
>                 *val = -(1 << (chan->scan_type.realbits - 1));
>                 return IIO_VAL_INT;
> +       case IIO_CHAN_INFO_SAMP_FREQ:
> +               *val = st->filter;
> +               return IIO_VAL_INT;
>         }
> 
>         return -EINVAL;
>  }
> 
> +static int ad7780_write_raw(struct iio_dev *indio_dev,
> +                           struct iio_chan_spec const *chan,
> +                           int val,
> +                           int val2,
> +                           long m)
> +{
> +       struct ad7780_state *st = iio_priv(indio_dev);
> +       const struct ad7780_chip_info *chip_info = st->chip_info;
> +       int vref, gain;
> +       unsigned int full_scale;
> +
> +       if (!chip_info->is_ad778x)
> +               return 0;
> +
> +       switch (m) {
> +       case IIO_CHAN_INFO_SCALE:
> +               if (val != 0)
> +                       return -EINVAL;
> +
> +               vref = st->int_vref_mv * 1000000LL;

From the datasheet, the VREF is ±5 V, therefore your vref variable will
overflow. You probably need unsigned long long.

> +               full_scale = 1 << (chip_info->channel.scane_type.realbis
> - 1);
> +               gain = DIV_ROUND_CLOSEST(vref, full_scale);
> +               gain = DIV_ROUND_CLOSEST(gain, val2);
> +               st->gain = gain;
> +               if (gain < AD7780_GAIN_MIDPOINT)
> +                       gain = 0;
> +               else
> +                       gain = 1;
> +               gpiod_set_value(st->gain_gpio, gain);
> +       break;
> +       case IIO_CHAN_INFO_SAMP_FREQ:
> +               if (1000*val + val2/1000 < AD7780_FILTER_MIDPOINT)
> +                       val = 0;
> +               else
> +                       val = 1;
> +               st->filter = ad778x_filter[val];
> +               gpiod_set_value(st->filter_gpio, val);
> +       break;
> +       }
> +
> +       return 0;
> +}
> +
>  static int ad7780_postprocess_sample(struct ad_sigma_delta *sigma_delta,
>                                      unsigned int raw_sample)
>  {
> @@ -126,10 +187,8 @@ static int ad7780_postprocess_sample(struct
> ad_sigma_delta *sigma_delta,
>                 return -EIO;
> 
>         if (chip_info->is_ad778x) {
> -               if (raw_sample & AD7780_GAIN)
> -                       st->gain = 1;
> -               else
> -                       st->gain = 128;
> +               st->gain = ad778x_gain[raw_sample & AD7780_GAIN];
> +               st->filter = ad778x_filter[raw_sample & AD7780_FILTER];
>         }
> 
>         return 0;
> @@ -141,18 +200,20 @@ static const struct ad_sigma_delta_info
> ad7780_sigma_delta_info = {
>         .has_registers = false,
>  };
> 
> -#define AD7780_CHANNEL(bits, wordsize) \
> +#define AD7170_CHANNEL(bits, wordsize) \
>         AD_SD_CHANNEL_NO_SAMP_FREQ(1, 0, 0, bits, 32, wordsize - bits)
> +#define AD7780_CHANNEL(bits, wordsize) \
> +       AD_SD_CHANNEL_GAIN_FILTER(1, 0, 0, bits, 32, wordsize - bits)
> 
>  static const struct ad7780_chip_info ad7780_chip_info_tbl[] = {
>         [ID_AD7170] = {
> -               .channel = AD7780_CHANNEL(12, 24),
> +               .channel = AD7170_CHANNEL(12, 24),
>                 .pattern = AD7170_PATTERN,
>                 .pattern_mask = AD7170_PATTERN_MASK,
>                 .is_ad778x = false,
>         },
>         [ID_AD7171] = {
> -               .channel = AD7780_CHANNEL(16, 24),
> +               .channel = AD7170_CHANNEL(16, 24),
>                 .pattern = AD7170_PATTERN,
>                 .pattern_mask = AD7170_PATTERN_MASK,
>                 .is_ad778x = false,
> @@ -173,6 +234,7 @@ static const struct ad7780_chip_info
> ad7780_chip_info_tbl[] = {
> 
>  static const struct iio_info ad7780_info = {
>         .read_raw = ad7780_read_raw,
> +       .write_raw = ad7780_write_raw,
>  };
> 
>  static int ad7780_probe(struct spi_device *spi)
> @@ -222,6 +284,29 @@ static int ad7780_probe(struct spi_device *spi)
>                 goto error_disable_reg;
>         }
> 
> +       if (st->chip_info->is_ad778x) {
> +               st->gain_gpio = devm_gpiod_get_optional(&spi->dev,
> +                                                       "gain",
> +                                                       GPIOD_OUT_HIGH);
> +               if (IS_ERR(st->gain_gpio)) {
> +                       ret = PTR_ERR(st->gain_gpio);
> +                       dev_err(&spi->dev, "Failed to request gain GPIO:
> %d\n",
> +                               ret);
> +                       goto error_disable_reg;
> +               }
> +
> +               st->filter_gpio = devm_gpiod_get_optional(&spi->dev,
> +                                                         "filter",
> +                                                         GPIOD_OUT_HIGH)
> ;
> +               if (IS_ERR(st->filter_gpio)) {
> +                       ret = PTR_ERR(st->filter_gpio);
> +                       dev_err(&spi->dev,
> +                               "Failed to request filter GPIO: %d\n",
> +                               ret);
> +                       goto error_disable_reg;
> +               }
> +       }
> +
>         ret = ad_sd_setup_buffer_and_trigger(indio_dev);
>         if (ret)
>                 goto error_disable_reg;
> diff --git a/include/linux/iio/adc/ad_sigma_delta.h
> b/include/linux/iio/adc/ad_sigma_delta.h
> index 7e84351fa2c0..c01da869de83 100644
> --- a/include/linux/iio/adc/ad_sigma_delta.h
> +++ b/include/linux/iio/adc/ad_sigma_delta.h
> @@ -176,6 +176,11 @@ int ad_sd_validate_trigger(struct iio_dev
> *indio_dev, struct iio_trigger *trig);
>         __AD_SD_CHANNEL(_si, _channel, -1, _address, _bits, \
>                 _storagebits, _shift, NULL, IIO_VOLTAGE, 0)
> 
> +#define AD_SD_CHANNEL_GAIN_FILTER(_si, _channel, _address, _bits, \
> +       _storagebits, _shift) \
> +       __AD_SD_CHANNEL(_si, _channel, -1, _address, _bits, \
> +               _storagebits, _shift, NULL, IIO_VOLTAGE,
> BIT(IIO_CHAN_INFO_RAW))
> +

Do you need to define a new macro?

>  #define AD_SD_TEMP_CHANNEL(_si, _address, _bits, _storagebits, _shift) \
>         __AD_SD_CHANNEL(_si, 0, -1, _address, _bits, \
>                 _storagebits, _shift, NULL, IIO_TEMP, \
> --
> 2.20.1
>