[PATCH linux dev-4.10 1/2] drivers/iio: dps310 Temperature measurement fix.

[Joel Stanley]

On Tue, Jul 25, 2017 at 6:55 AM, Christopher Bostic
<cbostic at linux.vnet.ibm.com> wrote:
> Add a manufacturer's suggested workaround to deal with early revisions
> of chip that don't indicate correct temperature.  Readings can be in the
> ~60C range when they should be in the ~20's.
>
> Signed-off-by: Christopher Bostic <cbostic at linux.vnet.ibm.com>

Looks okay Chris. Has there been an errata issued for the device so I
can check what we're doing here?

I don't think there's much value in the #defines without meaningful
labels, so I removed them when applying the patch.

Cheers,

Joel

> ---
>  drivers/iio/pressure/dps310.c | 49 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 48 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
> index 1b54ae0..f351c26 100644
> --- a/drivers/iio/pressure/dps310.c
> +++ b/drivers/iio/pressure/dps310.c
> @@ -56,7 +56,12 @@
>  #define  DPS310_FIFO_EN                BIT(5)
>  #define  DPS310_SPI_EN         BIT(6)
>  #define DPS310_RESET           0x0c
> +#define DPS310_TEMP_FIX_E      0x0e
> +#define DPS310_TEMP_FIX_F      0x0f
>  #define  DPS310_RESET_MAGIC    (BIT(0) | BIT(3))
> +#define DPS310_TEMP_FIX_32     0x32
> +#define  DPS310_TEMP_ERR_FIXED BIT(1)
> +#define DPS310_TEMP_FIX_62     0x62
>  #define DPS310_COEF_BASE       0x10
>
>  #define DPS310_PRS_BASE                DPS310_PRS_B0
> @@ -219,6 +224,9 @@ static bool dps310_is_writeable_reg(struct device *dev, unsigned int reg)
>         case DPS310_MEAS_CFG:
>         case DPS310_CFG_REG:
>         case DPS310_RESET:
> +       case DPS310_TEMP_FIX_E:
> +       case DPS310_TEMP_FIX_F:
> +       case DPS310_TEMP_FIX_62:
>                 return true;
>         default:
>                 return false;
> @@ -308,7 +316,7 @@ static int dps310_read_raw(struct iio_dev *iio,
>         .writeable_reg = dps310_is_writeable_reg,
>         .volatile_reg = dps310_is_volatile_reg,
>         .cache_type = REGCACHE_RBTREE,
> -       .max_register = 0x29,
> +       .max_register = 0x62,
>  };
>
>  static const struct iio_info dps310_info = {
> @@ -317,6 +325,41 @@ static int dps310_read_raw(struct iio_dev *iio,
>         .write_raw = dps310_write_raw,
>  };
>
> +/*
> + * Some verions of chip will read temperatures in the ~60C range when
> + * its acutally ~20C. This is the manufacturer recommended workaround
> + * to correct the issue.
> + */
> +static int dps310_temp_workaround(struct dps310_data *data)
> +{
> +       int r, reg;
> +
> +       r = regmap_read(data->regmap, DPS310_TEMP_FIX_32, &reg);
> +       if (r < 0)
> +               return r;
> +
> +       if (!(reg & DPS310_TEMP_ERR_FIXED)) {
> +               r = regmap_write(data->regmap, DPS310_TEMP_FIX_E, 0xA5);
> +               if (r < 0)
> +                       return r;
> +
> +               r = regmap_write(data->regmap, DPS310_TEMP_FIX_F, 0x96);
> +               if (r < 0)
> +                       return r;
> +
> +               r = regmap_write(data->regmap, DPS310_TEMP_FIX_62, 0x02);
> +               if (r < 0)
> +                       return r;
> +
> +               r = regmap_write(data->regmap, DPS310_TEMP_FIX_E, 0x00);
> +               if (r < 0)
> +                       return r;
> +
> +               r = regmap_write(data->regmap, DPS310_TEMP_FIX_F, 0x00);
> +       }
> +       return r;
> +}
> +
>  static int dps310_probe(struct i2c_client *client,
>                         const struct i2c_device_id *id)
>  {
> @@ -379,6 +422,10 @@ static int dps310_probe(struct i2c_client *client,
>         if (r < 0)
>                 return r;
>
> +       r = dps310_temp_workaround(data);
> +       if (r < 0)
> +               return r;
> +
>         r = devm_iio_device_register(&client->dev, iio);
>         if (r)
>                 return r;
> --
> 1.8.2.2
>