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

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Message-ID: <CAJCx=gn0Yv+oP56HQQNm-9JbH2aoZuEQ-73b1grLTVNfbYsDsg@mail.gmail.com>
Date:   Thu, 9 May 2019 11:09:56 +0800
From:   Matt Ranostay <matt.ranostay@...sulko.com>
To:     Eddie James <eajames@...ux.ibm.com>
Cc:     "open list:IIO SUBSYSTEM AND DRIVERS" <linux-iio@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>, joel@....id.au,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Hartmut Knaack <knaack.h@....de>,
        Jonathan Cameron <jic23@...nel.org>,
        Christopher Bostic <cbostic@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 2/3] iio: dps310: Temperature measurement errata

On Thu, May 9, 2019 at 3:36 AM Eddie James <eajames@...ux.ibm.com> wrote:
>
> From: Christopher Bostic <cbostic@...ux.vnet.ibm.com>
>
> 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@...ux.vnet.ibm.com>
> Signed-off-by: Joel Stanley <joel@....id.au>
> Signed-off-by: Eddie James <eajames@...ux.ibm.com>
> ---
>  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

>                 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
>