[PATCH v1 14/17] iio: chemical: bme680: Modify startup procedure

[Vasileios Amoiridis <vassilisamir@gmail.com>]

Modify the startup procedure to reflect the procedure of
the Bosch BME68x Sensor API. The initial readings and
configuration of the sensor need to happen in the
following order:

1) Read calibration data [1,2]
2) Chip general configuration [3]
3) Gas configuration [4]

After the chip configuration it is necessary to ensure that
the sensor is in sleeping mode, in order to apply the gas
configuration settings [5].

Also, after the soft reset, it is advised to wait for 5ms [6].

[1]: https://github.com/boschsensortec/BME68x_SensorAPI/blob/v4.4.8/bme68x.c#L162
[2]: https://github.com/boschsensortec/BME68x_SensorAPI/blob/v4.4.8/examples/forced_mode/forced_mode.c#L44
[3]: https://github.com/boschsensortec/BME68x_SensorAPI/blob/v4.4.8/examples/forced_mode/forced_mode.c#L53
[4]: https://github.com/boschsensortec/BME68x_SensorAPI/blob/v4.4.8/examples/forced_mode/forced_mode.c#L60
[5]: https://github.com/boschsensortec/BME68x_SensorAPI/blob/v4.4.8/bme68x.c#L640
[6]: https://github.com/boschsensortec/BME68x_SensorAPI/blob/v4.4.8/bme68x.c#L294
Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
---
 drivers/iio/chemical/bme680.h      |  2 ++
 drivers/iio/chemical/bme680_core.c | 27 ++++++++++++++++++---------
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/drivers/iio/chemical/bme680.h b/drivers/iio/chemical/bme680.h
index 17ea59253923..3be2f76a5bfb 100644
--- a/drivers/iio/chemical/bme680.h
+++ b/drivers/iio/chemical/bme680.h
@@ -61,6 +61,8 @@
 
 #define BME680_MEAS_TRIM_MASK			GENMASK(24, 4)
 
+#define BME680_STARTUP_TIME_US			5000
+
 /* Calibration Parameters */
 #define BME680_T2_LSB_REG	0x8A
 #define BME680_H2_MSB_REG	0xE1
diff --git a/drivers/iio/chemical/bme680_core.c b/drivers/iio/chemical/bme680_core.c
index b055eeee8f1c..afaa43ec3241 100644
--- a/drivers/iio/chemical/bme680_core.c
+++ b/drivers/iio/chemical/bme680_core.c
@@ -505,10 +505,12 @@ static int bme680_chip_config(struct bme680_data *data)
 	ret = regmap_write_bits(data->regmap, BME680_REG_CTRL_MEAS,
 				BME680_OSRS_TEMP_MASK | BME680_OSRS_PRESS_MASK,
 				osrs);
-	if (ret < 0)
+	if (ret < 0) {
 		dev_err(dev, "failed to write ctrl_meas register\n");
+		return ret;
+	}
 
-	return ret;
+	return 0;
 }
 
 static int bme680_gas_config(struct bme680_data *data)
@@ -517,6 +519,11 @@ static int bme680_gas_config(struct bme680_data *data)
 	int ret;
 	u8 heatr_res, heatr_dur;
 
+	/* Go to sleep */
+	ret = bme680_set_mode(data, false);
+	if (ret < 0)
+		return ret;
+
 	heatr_res = bme680_calc_heater_res(data, data->heater_temp);
 
 	/* set target heater temperature */
@@ -847,6 +854,8 @@ int bme680_core_probe(struct device *dev, struct regmap *regmap,
 		return ret;
 	}
 
+	usleep_range(BME680_STARTUP_TIME_US, BME680_STARTUP_TIME_US + 1000);
+
 	ret = regmap_read(regmap, BME680_REG_CHIP_ID, &data->check);
 	if (ret < 0) {
 		dev_err(dev, "Error reading chip ID\n");
@@ -859,22 +868,22 @@ int bme680_core_probe(struct device *dev, struct regmap *regmap,
 		return -ENODEV;
 	}
 
-	ret = bme680_chip_config(data);
+	ret = bme680_read_calib(data, &data->bme680);
 	if (ret < 0) {
-		dev_err(dev, "failed to set chip_config data\n");
+		dev_err(dev,
+			"failed to read calibration coefficients at probe\n");
 		return ret;
 	}
 
-	ret = bme680_gas_config(data);
+	ret = bme680_chip_config(data);
 	if (ret < 0) {
-		dev_err(dev, "failed to set gas config data\n");
+		dev_err(dev, "failed to set chip_config data\n");
 		return ret;
 	}
 
-	ret = bme680_read_calib(data, &data->bme680);
+	ret = bme680_gas_config(data);
 	if (ret < 0) {
-		dev_err(dev,
-			"failed to read calibration coefficients at probe\n");
+		dev_err(dev, "failed to set gas config data\n");
 		return ret;
 	}
 
-- 
2.25.1