[PATCH v4 2/7] iio: pressure: bmp280: Add support for bmp280 soft reset

[Vasileios Amoiridis <vassilisamir@xxxxxxxxx>]

The BM(P/E)28x devices have an option for soft reset which is also
recommended by the Bosch Sensortech BME2 Sensor API to be used before the
initial configuration of the device.

Link: https://github.com/boschsensortec/BME280_SensorAPI/blob/bme280_v3.5.1/bme280.c#L429
Signed-off-by: Vasileios Amoiridis <vassilisamir@xxxxxxxxx>
---
 drivers/iio/pressure/bmp280-core.c | 31 ++++++++++++++++++++++++++++++
 drivers/iio/pressure/bmp280.h      |  3 +++
 2 files changed, 34 insertions(+)

diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
index 9c705f2c4a7b..193a8fcbb5d8 100644
--- a/drivers/iio/pressure/bmp280-core.c
+++ b/drivers/iio/pressure/bmp280-core.c
@@ -965,6 +965,35 @@ static const unsigned long bme280_avail_scan_masks[] = {
 	0
 };
 
+static int bmp280_preinit(struct bmp280_data *data)
+{
+	unsigned int reg;
+	int ret;
+
+	ret = regmap_write(data->regmap, BMP280_REG_RESET, BMP280_RST_SOFT_CMD);
+	if (ret)
+		return dev_err_probe(data->dev, ret,
+				     "Failed to reset device.\n");
+
+	/*
+	 * According to the datasheet in Chapter 1: Specification, Table 2,
+	 * after resetting, the device uses the complete power-on sequence so
+	 * it needs to wait for the defined start-up time.
+	 */
+	fsleep(data->start_up_time);
+
+	ret = regmap_read(data->regmap, BMP280_REG_STATUS, &reg);
+	if (ret)
+		return dev_err_probe(data->dev, ret,
+				     "Failed to read status register.\n");
+
+	if (reg & BMP280_REG_STATUS_IM_UPDATE)
+		return dev_err_probe(data->dev, -EIO,
+				     "Failed to copy NVM contents.\n");
+
+	return 0;
+}
+
 static int bmp280_chip_config(struct bmp280_data *data)
 {
 	u8 osrs = FIELD_PREP(BMP280_OSRS_TEMP_MASK, data->oversampling_temp + 1) |
@@ -1082,6 +1111,7 @@ const struct bmp280_chip_info bmp280_chip_info = {
 	.read_temp = bmp280_read_temp,
 	.read_press = bmp280_read_press,
 	.read_calib = bmp280_read_calib,
+	.preinit = bmp280_preinit,
 
 	.trigger_handler = bmp280_trigger_handler,
 };
@@ -1202,6 +1232,7 @@ const struct bmp280_chip_info bme280_chip_info = {
 	.read_press = bmp280_read_press,
 	.read_humid = bme280_read_humid,
 	.read_calib = bme280_read_calib,
+	.preinit = bmp280_preinit,
 
 	.trigger_handler = bme280_trigger_handler,
 };
diff --git a/drivers/iio/pressure/bmp280.h b/drivers/iio/pressure/bmp280.h
index 4e675401d61b..73516878d020 100644
--- a/drivers/iio/pressure/bmp280.h
+++ b/drivers/iio/pressure/bmp280.h
@@ -205,6 +205,9 @@
 #define BMP280_REG_CONFIG		0xF5
 #define BMP280_REG_CTRL_MEAS		0xF4
 #define BMP280_REG_STATUS		0xF3
+#define BMP280_REG_STATUS_IM_UPDATE	BIT(0)
+#define BMP280_REG_RESET		0xE0
+#define BMP280_RST_SOFT_CMD		0xB6
 
 #define BMP280_REG_COMP_TEMP_START	0x88
 #define BMP280_COMP_TEMP_REG_COUNT	6
-- 
2.25.1