Re: [PATCH v2 2/3] iio: dps310: Temperature measurement errata

[Eddie James]

On 5/8/19 10:09 PM, Matt Ranostay wrote:
> On Thu, May 9, 2019 at 3:36 AM Eddie James <eajames@xxxxxxxxxxxxx> wrote:
> > From: Christopher Bostic <cbostic@xxxxxxxxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Joel Stanley <joel@xxxxxxxxx>
> > Signed-off-by: Eddie James <eajames@xxxxxxxxxxxxx>
> > ---
> >   drivers/iio/pressure/dps310.c | 51 ++++++++++++++++++++++++++++++++++++++++++-
> >   1 file changed, 50 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
> > index 7afaa88..c42808e 100644
> > --- a/drivers/iio/pressure/dps310.c
> > +++ b/drivers/iio/pressure/dps310.c
> > @@ -221,6 +221,9 @@ static bool dps310_is_writeable_reg(struct device *dev, unsigned int reg)
> >          case DPS310_MEAS_CFG:
> >          case DPS310_CFG_REG:
> >          case DPS310_RESET:
> > +       case 0x0e:
> > +       case 0x0f:
> > +       case 0x62:
> What is with the magic values? Are they not documented to what they
> are, and hence not defining enum values for them?
>
> - Matt


Thats correct. These don't show up in the data sheet so I left them as 
raw values. Chris, do you know what the source for these values was?

Thanks,

Eddie


> >                  return true;
> >          default:
> >                  return false;
> > @@ -237,6 +240,7 @@ static bool dps310_is_volatile_reg(struct device *dev, unsigned int reg)
> >          case DPS310_TMP_B1:
> >          case DPS310_TMP_B2:
> >          case DPS310_MEAS_CFG:
> > +       case 0x32:
> >                  return true;
> >          default:
> >                  return false;
> > @@ -314,7 +318,7 @@ 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 = {
> > @@ -322,6 +326,47 @@ 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 actually ~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, 0x32, &reg);
> > +       if (r < 0)
> > +               return r;
> > +
> > +       /*
> > +        * If bit 1 is set then the device is okay, and the workaround does not
> > +        * need to be applied
> > +        */
> > +       if (reg & BIT(1))
> > +               return 0;
> > +
> > +       r = regmap_write(data->regmap, 0x0e, 0xA5);
> > +       if (r < 0)
> > +               return r;
> > +
> > +       r = regmap_write(data->regmap, 0x0f, 0x96);
> > +       if (r < 0)
> > +               return r;
> > +
> > +       r = regmap_write(data->regmap, 0x62, 0x02);
> > +       if (r < 0)
> > +               return r;
> > +
> > +       r = regmap_write(data->regmap, 0x0e, 0x00);
> > +       if (r < 0)
> > +               return r;
> > +
> > +       r = regmap_write(data->regmap, 0x0f, 0x00);
> > +
> > +       return r;
> > +}
> > +
> >   static int dps310_probe(struct i2c_client *client,
> >                          const struct i2c_device_id *id)
> >   {
> > @@ -383,6 +428,10 @@ static int dps310_probe(struct i2c_client *client,
> >          if (r < 0)
> >                  goto err;
> >
> > +       r = dps310_temp_workaround(data);
> > +       if (r < 0)
> > +               return r;
> > +
> >          r = devm_iio_device_register(&client->dev, iio);
> >          if (r)
> >                  goto err;
> > --
> > 1.8.3.1