linux-kernel - Re: [PATCH v2 2/3] iio: temperature: mlx90632 Read sampling frequency

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Date:   Sun, 4 Sep 2022 17:23:16 +0200
From:   Crt Mori <cmo@...exis.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH v2 2/3] iio: temperature: mlx90632 Read sampling frequency

On Sun, 4 Sept 2022 at 17:19, Jonathan Cameron <jic23@...nel.org> wrote:
>
> On Sun,  4 Sep 2022 00:24:02 +0200
> cmo@...exis.com wrote:
>
> > From: Crt Mori <cmo@...exis.com>
> >
> > Allow users to read sensor sampling frequency to better plan the
> > application measurement requests.
>
> I didn't read this closely enough.  Why is the frequency read only?
> We'd not normally have an available attribute in that case, because
> the values aren't available if we have no way to set the value.
>

It is writable, but so far I did not want to include the change part,
because it is writing to EEPROM and that means sensor slowly gets
killed as memory has limited number of write cycles.

> Jonathan
>
> >
> > Signed-off-by: Crt Mori <cmo@...exis.com>
> > ---
> >  drivers/iio/temperature/mlx90632.c | 44 ++++++++++++++++++++++++++++++
> >  1 file changed, 44 insertions(+)
> >
> > diff --git a/drivers/iio/temperature/mlx90632.c b/drivers/iio/temperature/mlx90632.c
> > index 9acd819c76a6..37edd324d6a1 100644
> > --- a/drivers/iio/temperature/mlx90632.c
> > +++ b/drivers/iio/temperature/mlx90632.c
> > @@ -80,6 +80,9 @@
> >  #define MLX90632_PWR_STATUS_CONTINUOUS MLX90632_PWR_STATUS(3) /* continuous */
> >
> >  #define MLX90632_EE_RR(ee_val) (ee_val & GENMASK(10, 8)) /* Only Refresh Rate bits */
> > +#define MLX90632_REFRESH_RATE(ee_val) (MLX90632_EE_RR(ee_val) >> 8)
> > +                                     /* Extract Refresh Rate from ee register */
> > +#define MLX90632_REFRESH_RATE_STATUS(refresh_rate) (refresh_rate << 8)
> >
> >  /* Measurement types */
> >  #define MLX90632_MTYP_MEDICAL 0
> > @@ -908,6 +911,24 @@ static int mlx90632_calc_ambient_dsp105(struct mlx90632_data *data, int *val)
> >       return ret;
> >  }
> >
> > +static int mlx90632_get_refresh_rate(struct mlx90632_data *data,
> > +                                  int *refresh_rate)
> > +{
> > +     unsigned int meas1;
> > +     int ret;
> > +
> > +     ret = regmap_read(data->regmap, MLX90632_EE_MEDICAL_MEAS1, &meas1);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     *refresh_rate = MLX90632_REFRESH_RATE(meas1);
> > +
> > +     return ret;
> > +}
> > +
> > +static const int mlx90632_freqs[][2] = { {0, 500000}, {1, 0}, {2, 0}, {4, 0},
> > +                                       {8, 0}, {16, 0}, {32, 0}, {64, 0} };
> > +
> >  static int mlx90632_pm_interraction_wakeup(struct mlx90632_data *data)
> >  {
> >       unsigned long now;
> > @@ -978,6 +999,15 @@ static int mlx90632_read_raw(struct iio_dev *indio_dev,
> >               *val = data->object_ambient_temperature;
> >               ret = IIO_VAL_INT;
> >               break;
> > +     case IIO_CHAN_INFO_SAMP_FREQ:
> > +             ret = mlx90632_get_refresh_rate(data, &cr);
> > +             if (ret < 0)
> > +                     goto mlx90632_read_raw_pm;
> > +
> > +             *val = mlx90632_freqs[cr][0];
> > +             *val2 = mlx90632_freqs[cr][1];
> > +             ret = IIO_VAL_INT_PLUS_MICRO;
> > +             break;
> >       default:
> >               ret = -EINVAL;
> >               break;
> > @@ -1012,12 +1042,24 @@ static int mlx90632_write_raw(struct iio_dev *indio_dev,
> >       }
> >  }
> >
> > +static IIO_CONST_ATTR(sampling_frequency_available, "0.5 1 2 4 8 16 32 64");
> > +
> > +static struct attribute *mlx90632_attributes[] = {
> > +     &iio_const_attr_sampling_frequency_available.dev_attr.attr,
> > +     NULL
> > +};
> > +
> > +static const struct attribute_group mlx90632_attribute_group = {
> > +     .attrs = mlx90632_attributes,
> > +};
> > +
> >  static const struct iio_chan_spec mlx90632_channels[] = {
> >       {
> >               .type = IIO_TEMP,
> >               .modified = 1,
> >               .channel2 = IIO_MOD_TEMP_AMBIENT,
> >               .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> > +             .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
> >       },
> >       {
> >               .type = IIO_TEMP,
> > @@ -1025,12 +1067,14 @@ static const struct iio_chan_spec mlx90632_channels[] = {
> >               .channel2 = IIO_MOD_TEMP_OBJECT,
> >               .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
> >                       BIT(IIO_CHAN_INFO_CALIBEMISSIVITY) | BIT(IIO_CHAN_INFO_CALIBAMBIENT),
> > +             .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
> >       },
> >  };
> >
> >  static const struct iio_info mlx90632_info = {
> >       .read_raw = mlx90632_read_raw,
> >       .write_raw = mlx90632_write_raw,
> > +     .attrs = &mlx90632_attribute_group,
> >  };
> >
> >  static int mlx90632_sleep(struct mlx90632_data *data)
>