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SubjectRe: [PATCH v3 2/3] iio: dps310: Temperature measurement errata
On Wed, 15 May 2019 13:41:16 -0500
Eddie James <eajames@linux.ibm.com> wrote:

> From: Christopher Bostic <cbostic@linux.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@linux.vnet.ibm.com>
> Signed-off-by: Joel Stanley <joel@jms.id.au>
> Signed-off-by: Eddie James <eajames@linux.ibm.com>
Looks fine to me.

For reference:

Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
> drivers/iio/pressure/dps310.c | 52 +++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 50 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
> index 9acfccb..a093e3a 100644
> --- a/drivers/iio/pressure/dps310.c
> +++ b/drivers/iio/pressure/dps310.c
> @@ -53,7 +53,6 @@
> #define DPS310_RESET 0x0c
> #define DPS310_RESET_MAGIC 0x09
> #define DPS310_COEF_BASE 0x10
> -#define DPS310_COEF_SRC 0x28
>
> /* Make sure sleep time is <= 20ms for usleep_range */
> #define DPS310_POLL_SLEEP_US(t) min(20000, (t) / 8)
> @@ -234,6 +233,10 @@ static bool dps310_is_writeable_reg(struct device *dev, unsigned int reg)
> case DPS310_MEAS_CFG:
> case DPS310_CFG_REG:
> case DPS310_RESET:
> + /* No documentation available on the registers below */
> + case 0x0e:
> + case 0x0f:
> + case 0x62:
> return true;
> default:
> return false;
> @@ -250,6 +253,7 @@ 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: /* No documentation available on this register */
> return true;
> default:
> return false;
> @@ -360,7 +364,7 @@ static void dps310_reset(void *action_data)
> .writeable_reg = dps310_is_writeable_reg,
> .volatile_reg = dps310_is_volatile_reg,
> .cache_type = REGCACHE_RBTREE,
> - .max_register = DPS310_COEF_SRC,
> + .max_register = 0x62, /* No documentation available on this register */
> };
>
> static const struct iio_info dps310_info = {
> @@ -368,6 +372,46 @@ static void dps310_reset(void *action_data)
> .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. The registers used below are undocumented.
> + */
> +static int dps310_temp_workaround(struct dps310_data *data)
> +{
> + int rc;
> + int reg;
> +
> + rc = regmap_read(data->regmap, 0x32, &reg);
> + if (rc < 0)
> + return rc;
> +
> + /*
> + * 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;
> +
> + rc = regmap_write(data->regmap, 0x0e, 0xA5);
> + if (rc < 0)
> + return rc;
> +
> + rc = regmap_write(data->regmap, 0x0f, 0x96);
> + if (rc < 0)
> + return rc;
> +
> + rc = regmap_write(data->regmap, 0x62, 0x02);
> + if (rc < 0)
> + return rc;
> +
> + rc = regmap_write(data->regmap, 0x0e, 0x00);
> + if (rc < 0)
> + return rc;
> +
> + return regmap_write(data->regmap, 0x0f, 0x00);
> +}
> +
> static int dps310_probe(struct i2c_client *client,
> const struct i2c_device_id *id)
> {
> @@ -439,6 +483,10 @@ static int dps310_probe(struct i2c_client *client,
> if (rc < 0)
> return rc;
>
> + rc = dps310_temp_workaround(data);
> + if (rc < 0)
> + return rc;
> +
> rc = devm_iio_device_register(&client->dev, iio);
> if (rc)
> return rc;

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