[PATCH v3 0/2] iio: pressure: dps310: Reset chip if MEAS_CFG is corrupt

[PATCH v3 0/2] iio: pressure: dps310: Reset chip if MEAS_CFG is corrupt

[Eddie James]

Corruption of the MEAS_CFG register has been observed soon after
system boot. In order to recover this scenario, check MEAS_CFG if
measurement isn't ready, and if it's incorrect, reset the DPS310
and execute the startup procedure. Include a patch to move the
startup procedure into a function.

Changes since v2:
 - Add some comments
 - Fix the clunky control flow

Changes since v1:
 - Separate into two patches
 - Rename 'dps310_verify_meas_cfg' to 'dps310_check_reset_meas_cfg'

Eddie James (2):
  iio: pressure: dps310: Refactor startup procedure
  iio: pressure: dps310: Reset chip if MEAS_CFG is corrupt

 drivers/iio/pressure/dps310.c | 280 +++++++++++++++++++++-------------
 1 file changed, 176 insertions(+), 104 deletions(-)

-- 
2.27.0

[PATCH v3 1/2] iio: pressure: dps310: Refactor startup procedure

[Eddie James]

Move the startup procedure into a function, and correct a missing
check on the return code for writing the PRS_CFG register.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
---
 drivers/iio/pressure/dps310.c | 192 ++++++++++++++++++----------------
 1 file changed, 103 insertions(+), 89 deletions(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index 36fb7ae0d0a9..f79b274bb38d 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -159,6 +159,106 @@ static int dps310_get_coefs(struct dps310_data *data)
 	return 0;
 }
 
+/*
+ * 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_startup(struct dps310_data *data)
+{
+	int rc;
+	int ready;
+
+	/*
+	 * Set up pressure sensor in single sample, one measurement per second
+	 * mode
+	 */
+	rc = regmap_write(data->regmap, DPS310_PRS_CFG, 0);
+	if (rc < 0)
+		return rc;
+
+	/*
+	 * Set up external (MEMS) temperature sensor in single sample, one
+	 * measurement per second mode
+	 */
+	rc = regmap_write(data->regmap, DPS310_TMP_CFG, DPS310_TMP_EXT);
+	if (rc < 0)
+		return rc;
+
+	/* Temp and pressure shifts are disabled when PRC <= 8 */
+	rc = regmap_write_bits(data->regmap, DPS310_CFG_REG,
+			       DPS310_PRS_SHIFT_EN | DPS310_TMP_SHIFT_EN, 0);
+	if (rc < 0)
+		return rc;
+
+	/* MEAS_CFG doesn't update correctly unless first written with 0 */
+	rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
+			       DPS310_MEAS_CTRL_BITS, 0);
+	if (rc < 0)
+		return rc;
+
+	/* Turn on temperature and pressure measurement in the background */
+	rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
+			       DPS310_MEAS_CTRL_BITS, DPS310_PRS_EN |
+			       DPS310_TEMP_EN | DPS310_BACKGROUND);
+	if (rc < 0)
+		return rc;
+
+	/*
+	 * Calibration coefficients required for reporting temperature.
+	 * They are available 40ms after the device has started
+	 */
+	rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
+				      ready & DPS310_COEF_RDY, 10000, 40000);
+	if (rc < 0)
+		return rc;
+
+	rc = dps310_get_coefs(data);
+	if (rc < 0)
+		return rc;
+
+	rc = dps310_temp_workaround(data);
+	if (rc < 0)
+		return rc;
+
+	return 0;
+}
+
 static int dps310_get_pres_precision(struct dps310_data *data)
 {
 	int rc;
@@ -677,52 +777,12 @@ static const struct iio_info dps310_info = {
 	.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)
 {
 	struct dps310_data *data;
 	struct iio_dev *iio;
-	int rc, ready;
+	int rc;
 
 	iio = devm_iio_device_alloc(&client->dev,  sizeof(*data));
 	if (!iio)
@@ -747,54 +807,8 @@ static int dps310_probe(struct i2c_client *client,
 	if (rc)
 		return rc;
 
-	/*
-	 * Set up pressure sensor in single sample, one measurement per second
-	 * mode
-	 */
-	rc = regmap_write(data->regmap, DPS310_PRS_CFG, 0);
-
-	/*
-	 * Set up external (MEMS) temperature sensor in single sample, one
-	 * measurement per second mode
-	 */
-	rc = regmap_write(data->regmap, DPS310_TMP_CFG, DPS310_TMP_EXT);
-	if (rc < 0)
-		return rc;
-
-	/* Temp and pressure shifts are disabled when PRC <= 8 */
-	rc = regmap_write_bits(data->regmap, DPS310_CFG_REG,
-			       DPS310_PRS_SHIFT_EN | DPS310_TMP_SHIFT_EN, 0);
-	if (rc < 0)
-		return rc;
-
-	/* MEAS_CFG doesn't update correctly unless first written with 0 */
-	rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
-			       DPS310_MEAS_CTRL_BITS, 0);
-	if (rc < 0)
-		return rc;
-
-	/* Turn on temperature and pressure measurement in the background */
-	rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
-			       DPS310_MEAS_CTRL_BITS, DPS310_PRS_EN |
-			       DPS310_TEMP_EN | DPS310_BACKGROUND);
-	if (rc < 0)
-		return rc;
-
-	/*
-	 * Calibration coefficients required for reporting temperature.
-	 * They are available 40ms after the device has started
-	 */
-	rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
-				      ready & DPS310_COEF_RDY, 10000, 40000);
-	if (rc < 0)
-		return rc;
-
-	rc = dps310_get_coefs(data);
-	if (rc < 0)
-		return rc;
-
-	rc = dps310_temp_workaround(data);
-	if (rc < 0)
+	rc = dps310_startup(data);
+	if (rc)
 		return rc;
 
 	rc = devm_iio_device_register(&client->dev, iio);
-- 
2.27.0

[PATCH v3 2/2] iio: pressure: dps310: Reset chip if MEAS_CFG is corrupt

[Eddie James]

Corruption of the MEAS_CFG register has been observed soon after
system boot. In order to recover this scenario, check MEAS_CFG if
measurement isn't ready, and if it's incorrect, reset the DPS310
and execute the startup procedure.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
---
 drivers/iio/pressure/dps310.c | 88 +++++++++++++++++++++++++++++------
 1 file changed, 73 insertions(+), 15 deletions(-)

diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
index f79b274bb38d..fbceaa2cd71c 100644
--- a/drivers/iio/pressure/dps310.c
+++ b/drivers/iio/pressure/dps310.c
@@ -397,6 +397,44 @@ static int dps310_get_temp_k(struct dps310_data *data)
 	return scale_factors[ilog2(rc)];
 }
 
+/*
+ * Called with lock held. Returns a negative value on error, a positive value
+ * when the device is not ready, and zero when the device is ready.
+ */
+static int dps310_check_reset_meas_cfg(struct dps310_data *data, int ready_bit)
+{
+	int meas_cfg;
+	int rc = regmap_read(data->regmap, DPS310_MEAS_CFG, &meas_cfg);
+
+	if (rc < 0)
+		return rc;
+
+	/* Device is ready, proceed to measurement */
+	if (meas_cfg & ready_bit)
+		return 0;
+
+	/* Device is OK, just not ready */
+	if (meas_cfg & (DPS310_PRS_EN | DPS310_TEMP_EN | DPS310_BACKGROUND))
+		return 1;
+
+	/* DPS310 register state corrupt, better start from scratch */
+	rc = regmap_write(data->regmap, DPS310_RESET, DPS310_RESET_MAGIC);
+	if (rc < 0)
+		return rc;
+
+	/* Wait for device chip access: 2.5ms in specification */
+	usleep_range(2500, 12000);
+
+	/* Reinitialize the chip */
+	rc = dps310_startup(data);
+	if (rc)
+		return rc;
+
+	dev_info(&data->client->dev,
+		 "recovered from corrupted MEAS_CFG=%02x\n", meas_cfg);
+	return 1;
+}
+
 static int dps310_read_pres_raw(struct dps310_data *data)
 {
 	int rc;
@@ -409,16 +447,26 @@ static int dps310_read_pres_raw(struct dps310_data *data)
 	if (mutex_lock_interruptible(&data->lock))
 		return -EINTR;
 
-	rate = dps310_get_pres_samp_freq(data);
-	timeout = DPS310_POLL_TIMEOUT_US(rate);
-
-	/* Poll for sensor readiness; base the timeout upon the sample rate. */
-	rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
-				      ready & DPS310_PRS_RDY,
-				      DPS310_POLL_SLEEP_US(timeout), timeout);
-	if (rc)
+	rc = dps310_check_reset_meas_cfg(data, DPS310_PRS_RDY);
+	if (rc < 0)
 		goto done;
 
+	if (rc > 0) {
+		rate = dps310_get_pres_samp_freq(data);
+		timeout = DPS310_POLL_TIMEOUT_US(rate);
+
+		/*
+		 * Poll for sensor readiness; base the timeout upon the sample
+		 * rate.
+		 */
+		rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG,
+					      ready, ready & DPS310_PRS_RDY,
+					      DPS310_POLL_SLEEP_US(timeout),
+					      timeout);
+		if (rc)
+			goto done;
+	}
+
 	rc = regmap_bulk_read(data->regmap, DPS310_PRS_BASE, val, sizeof(val));
 	if (rc < 0)
 		goto done;
@@ -458,16 +506,26 @@ static int dps310_read_temp_raw(struct dps310_data *data)
 	if (mutex_lock_interruptible(&data->lock))
 		return -EINTR;
 
-	rate = dps310_get_temp_samp_freq(data);
-	timeout = DPS310_POLL_TIMEOUT_US(rate);
-
-	/* Poll for sensor readiness; base the timeout upon the sample rate. */
-	rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
-				      ready & DPS310_TMP_RDY,
-				      DPS310_POLL_SLEEP_US(timeout), timeout);
+	rc = dps310_check_reset_meas_cfg(data, DPS310_TMP_RDY);
 	if (rc < 0)
 		goto done;
 
+	if (rc > 0) {
+		rate = dps310_get_temp_samp_freq(data);
+		timeout = DPS310_POLL_TIMEOUT_US(rate);
+
+		/*
+		 * Poll for sensor readiness; base the timeout upon the sample
+		 * rate.
+		 */
+		rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG,
+					      ready, ready & DPS310_TMP_RDY,
+					      DPS310_POLL_SLEEP_US(timeout),
+					      timeout);
+		if (rc < 0)
+			goto done;
+	}
+
 	rc = dps310_read_temp_ready(data);
 
 done:
-- 
2.27.0

Re: [PATCH v3 2/2] iio: pressure: dps310: Reset chip if MEAS_CFG is corrupt

[Joel Stanley]

On Tue, 24 May 2022 at 20:17, Eddie James <eajames@linux.ibm.com> wrote:
>
> Corruption of the MEAS_CFG register has been observed soon after
> system boot. In order to recover this scenario, check MEAS_CFG if
> measurement isn't ready, and if it's incorrect, reset the DPS310
> and execute the startup procedure.
>
> Signed-off-by: Eddie James <eajames@linux.ibm.com>

Reviewed-by: Joel Stanley <joel@jms.id.au>

> ---
>  drivers/iio/pressure/dps310.c | 88 +++++++++++++++++++++++++++++------
>  1 file changed, 73 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
> index f79b274bb38d..fbceaa2cd71c 100644
> --- a/drivers/iio/pressure/dps310.c
> +++ b/drivers/iio/pressure/dps310.c
> @@ -397,6 +397,44 @@ static int dps310_get_temp_k(struct dps310_data *data)
>         return scale_factors[ilog2(rc)];
>  }
>
> +/*
> + * Called with lock held. Returns a negative value on error, a positive value
> + * when the device is not ready, and zero when the device is ready.
> + */
> +static int dps310_check_reset_meas_cfg(struct dps310_data *data, int ready_bit)
> +{
> +       int meas_cfg;
> +       int rc = regmap_read(data->regmap, DPS310_MEAS_CFG, &meas_cfg);
> +
> +       if (rc < 0)
> +               return rc;
> +
> +       /* Device is ready, proceed to measurement */
> +       if (meas_cfg & ready_bit)
> +               return 0;
> +
> +       /* Device is OK, just not ready */
> +       if (meas_cfg & (DPS310_PRS_EN | DPS310_TEMP_EN | DPS310_BACKGROUND))
> +               return 1;
> +
> +       /* DPS310 register state corrupt, better start from scratch */
> +       rc = regmap_write(data->regmap, DPS310_RESET, DPS310_RESET_MAGIC);
> +       if (rc < 0)
> +               return rc;
> +
> +       /* Wait for device chip access: 2.5ms in specification */
> +       usleep_range(2500, 12000);
> +
> +       /* Reinitialize the chip */
> +       rc = dps310_startup(data);
> +       if (rc)
> +               return rc;
> +
> +       dev_info(&data->client->dev,
> +                "recovered from corrupted MEAS_CFG=%02x\n", meas_cfg);
> +       return 1;
> +}
> +
>  static int dps310_read_pres_raw(struct dps310_data *data)
>  {
>         int rc;
> @@ -409,16 +447,26 @@ static int dps310_read_pres_raw(struct dps310_data *data)
>         if (mutex_lock_interruptible(&data->lock))
>                 return -EINTR;
>
> -       rate = dps310_get_pres_samp_freq(data);
> -       timeout = DPS310_POLL_TIMEOUT_US(rate);
> -
> -       /* Poll for sensor readiness; base the timeout upon the sample rate. */
> -       rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
> -                                     ready & DPS310_PRS_RDY,
> -                                     DPS310_POLL_SLEEP_US(timeout), timeout);
> -       if (rc)
> +       rc = dps310_check_reset_meas_cfg(data, DPS310_PRS_RDY);
> +       if (rc < 0)
>                 goto done;
>
> +       if (rc > 0) {
> +               rate = dps310_get_pres_samp_freq(data);
> +               timeout = DPS310_POLL_TIMEOUT_US(rate);
> +
> +               /*
> +                * Poll for sensor readiness; base the timeout upon the sample
> +                * rate.
> +                */
> +               rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG,
> +                                             ready, ready & DPS310_PRS_RDY,
> +                                             DPS310_POLL_SLEEP_US(timeout),
> +                                             timeout);
> +               if (rc)
> +                       goto done;
> +       }
> +
>         rc = regmap_bulk_read(data->regmap, DPS310_PRS_BASE, val, sizeof(val));
>         if (rc < 0)
>                 goto done;
> @@ -458,16 +506,26 @@ static int dps310_read_temp_raw(struct dps310_data *data)
>         if (mutex_lock_interruptible(&data->lock))
>                 return -EINTR;
>
> -       rate = dps310_get_temp_samp_freq(data);
> -       timeout = DPS310_POLL_TIMEOUT_US(rate);
> -
> -       /* Poll for sensor readiness; base the timeout upon the sample rate. */
> -       rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
> -                                     ready & DPS310_TMP_RDY,
> -                                     DPS310_POLL_SLEEP_US(timeout), timeout);
> +       rc = dps310_check_reset_meas_cfg(data, DPS310_TMP_RDY);
>         if (rc < 0)
>                 goto done;
>
> +       if (rc > 0) {
> +               rate = dps310_get_temp_samp_freq(data);
> +               timeout = DPS310_POLL_TIMEOUT_US(rate);
> +
> +               /*
> +                * Poll for sensor readiness; base the timeout upon the sample
> +                * rate.
> +                */
> +               rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG,
> +                                             ready, ready & DPS310_TMP_RDY,
> +                                             DPS310_POLL_SLEEP_US(timeout),
> +                                             timeout);
> +               if (rc < 0)
> +                       goto done;
> +       }
> +
>         rc = dps310_read_temp_ready(data);
>
>  done:
> --
> 2.27.0
>

Re: [PATCH v3 1/2] iio: pressure: dps310: Refactor startup procedure

[Joel Stanley]

On Tue, 24 May 2022 at 20:17, Eddie James <eajames@linux.ibm.com> wrote:
>
> Move the startup procedure into a function, and correct a missing
> check on the return code for writing the PRS_CFG register.
>
> Signed-off-by: Eddie James <eajames@linux.ibm.com>

Reviewed-by: Joel Stanley <joel@jms.id.au>

> ---
>  drivers/iio/pressure/dps310.c | 192 ++++++++++++++++++----------------
>  1 file changed, 103 insertions(+), 89 deletions(-)
>
> diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
> index 36fb7ae0d0a9..f79b274bb38d 100644
> --- a/drivers/iio/pressure/dps310.c
> +++ b/drivers/iio/pressure/dps310.c
> @@ -159,6 +159,106 @@ static int dps310_get_coefs(struct dps310_data *data)
>         return 0;
>  }
>
> +/*
> + * 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_startup(struct dps310_data *data)
> +{
> +       int rc;
> +       int ready;
> +
> +       /*
> +        * Set up pressure sensor in single sample, one measurement per second
> +        * mode
> +        */
> +       rc = regmap_write(data->regmap, DPS310_PRS_CFG, 0);
> +       if (rc < 0)
> +               return rc;
> +
> +       /*
> +        * Set up external (MEMS) temperature sensor in single sample, one
> +        * measurement per second mode
> +        */
> +       rc = regmap_write(data->regmap, DPS310_TMP_CFG, DPS310_TMP_EXT);
> +       if (rc < 0)
> +               return rc;
> +
> +       /* Temp and pressure shifts are disabled when PRC <= 8 */
> +       rc = regmap_write_bits(data->regmap, DPS310_CFG_REG,
> +                              DPS310_PRS_SHIFT_EN | DPS310_TMP_SHIFT_EN, 0);
> +       if (rc < 0)
> +               return rc;
> +
> +       /* MEAS_CFG doesn't update correctly unless first written with 0 */
> +       rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
> +                              DPS310_MEAS_CTRL_BITS, 0);
> +       if (rc < 0)
> +               return rc;
> +
> +       /* Turn on temperature and pressure measurement in the background */
> +       rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
> +                              DPS310_MEAS_CTRL_BITS, DPS310_PRS_EN |
> +                              DPS310_TEMP_EN | DPS310_BACKGROUND);
> +       if (rc < 0)
> +               return rc;
> +
> +       /*
> +        * Calibration coefficients required for reporting temperature.
> +        * They are available 40ms after the device has started
> +        */
> +       rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
> +                                     ready & DPS310_COEF_RDY, 10000, 40000);
> +       if (rc < 0)
> +               return rc;
> +
> +       rc = dps310_get_coefs(data);
> +       if (rc < 0)
> +               return rc;
> +
> +       rc = dps310_temp_workaround(data);
> +       if (rc < 0)
> +               return rc;
> +
> +       return 0;
> +}
> +
>  static int dps310_get_pres_precision(struct dps310_data *data)
>  {
>         int rc;
> @@ -677,52 +777,12 @@ static const struct iio_info dps310_info = {
>         .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)
>  {
>         struct dps310_data *data;
>         struct iio_dev *iio;
> -       int rc, ready;
> +       int rc;
>
>         iio = devm_iio_device_alloc(&client->dev,  sizeof(*data));
>         if (!iio)
> @@ -747,54 +807,8 @@ static int dps310_probe(struct i2c_client *client,
>         if (rc)
>                 return rc;
>
> -       /*
> -        * Set up pressure sensor in single sample, one measurement per second
> -        * mode
> -        */
> -       rc = regmap_write(data->regmap, DPS310_PRS_CFG, 0);
> -
> -       /*
> -        * Set up external (MEMS) temperature sensor in single sample, one
> -        * measurement per second mode
> -        */
> -       rc = regmap_write(data->regmap, DPS310_TMP_CFG, DPS310_TMP_EXT);
> -       if (rc < 0)
> -               return rc;
> -
> -       /* Temp and pressure shifts are disabled when PRC <= 8 */
> -       rc = regmap_write_bits(data->regmap, DPS310_CFG_REG,
> -                              DPS310_PRS_SHIFT_EN | DPS310_TMP_SHIFT_EN, 0);
> -       if (rc < 0)
> -               return rc;
> -
> -       /* MEAS_CFG doesn't update correctly unless first written with 0 */
> -       rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
> -                              DPS310_MEAS_CTRL_BITS, 0);
> -       if (rc < 0)
> -               return rc;
> -
> -       /* Turn on temperature and pressure measurement in the background */
> -       rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
> -                              DPS310_MEAS_CTRL_BITS, DPS310_PRS_EN |
> -                              DPS310_TEMP_EN | DPS310_BACKGROUND);
> -       if (rc < 0)
> -               return rc;
> -
> -       /*
> -        * Calibration coefficients required for reporting temperature.
> -        * They are available 40ms after the device has started
> -        */
> -       rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
> -                                     ready & DPS310_COEF_RDY, 10000, 40000);
> -       if (rc < 0)
> -               return rc;
> -
> -       rc = dps310_get_coefs(data);
> -       if (rc < 0)
> -               return rc;
> -
> -       rc = dps310_temp_workaround(data);
> -       if (rc < 0)
> +       rc = dps310_startup(data);
> +       if (rc)
>                 return rc;
>
>         rc = devm_iio_device_register(&client->dev, iio);
> --
> 2.27.0
>

Re: [PATCH v3 1/2] iio: pressure: dps310: Refactor startup procedure

[Andy Shevchenko]

On Tue, May 24, 2022 at 10:35 PM Eddie James <eajames@linux.ibm.com> wrote:
>
> Move the startup procedure into a function, and correct a missing
> check on the return code for writing the PRS_CFG register.

...

> +/*
> + * Some verions of chip will read temperatures in the ~60C range when

versions
of the chip(s)

> + * its actually ~20C. This is the manufacturer recommended workaround

it's

> + * to correct the issue. The registers used below are undocumented.
> + */

Yes, they are in the original code, but you may just fix while at it.

...

> +       rc = dps310_temp_workaround(data);
> +       if (rc < 0)

These ' < 0' parts are cargo cult, I believe.
That's why this makes code longer and confusing by "what is the
meaning of the positive values here?"

> +               return rc;
> +
> +       return 0;

That said,

  return dps310_temp_workaround(data);

should suffice.

-- 
With Best Regards,
Andy Shevchenko