[PATCH v6 2/2] iio: light: bh1750: Add hardware reset support via GPIO

[Sergio Perez <sergio@pereznus.es>]

Some BH1750 sensors require a hardware reset before they can be
detected on the I2C bus. This implementation adds support for an
optional reset GPIO that can be specified in the device tree.

The reset sequence pulls the GPIO low and then high before initializing
the sensor, which enables proper detection with tools like i2cdetect.
This is particularly important for sensors that power on in an
undefined state.

Signed-off-by: Sergio Perez <sergio@pereznus.es>
---
Revision history:
v5 => v6:
 - No changes
v4 => v5:
 - Logic change to be coherent with dt-binding as mentioned by Krzysztof Kozlowski
 - Adjust indentation as commented by Krzysztof Kozlowski
v3 => v4:
 - No changes
v2 => v3:
 - Split in two patches: dtbinding and code
 - Ensure list on mantainers following instructions by Krzysztof Kozlowski
 - Fix check tests as explainned by Krzysztof Kozlowski
v1 => v2:
 - Fixes some whitespaces and end lines
 - Remove unnecessary include
 - Use of fsleep rather than usleep_range as suggested by Jonathan Cameron
 - Use of dev_dbg to reduce innecessary output as suggested by Jonathan Cameron
 - Delete an extra function implementing the functionality inline as suggested by Jonathan Cameron
---
 drivers/iio/light/bh1750.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/iio/light/bh1750.c b/drivers/iio/light/bh1750.c
index 4b869fa9e5b1..764f88826fcb 100644
--- a/drivers/iio/light/bh1750.c
+++ b/drivers/iio/light/bh1750.c
@@ -22,12 +22,16 @@
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
 #include <linux/module.h>
+#include <linux/gpio/consumer.h>
 
 #define BH1750_POWER_DOWN		0x00
 #define BH1750_ONE_TIME_H_RES_MODE	0x20 /* auto-mode for BH1721 */
 #define BH1750_CHANGE_INT_TIME_H_BIT	0x40
 #define BH1750_CHANGE_INT_TIME_L_BIT	0x60
 
+/* Define the reset delay time in microseconds */
+#define BH1750_RESET_DELAY_US 10000 /* 10ms */
+
 enum {
 	BH1710,
 	BH1721,
@@ -40,6 +44,7 @@ struct bh1750_data {
 	struct mutex lock;
 	const struct bh1750_chip_info *chip_info;
 	u16 mtreg;
+	struct gpio_desc *reset_gpio;
 };
 
 struct bh1750_chip_info {
@@ -248,6 +253,25 @@ static int bh1750_probe(struct i2c_client *client)
 	data->client = client;
 	data->chip_info = &bh1750_chip_info_tbl[id->driver_data];
 
+	/* Get reset GPIO from device tree */
+	data->reset_gpio = devm_gpiod_get_optional(&client->dev,
+						   "reset", GPIOD_OUT_HIGH);
+
+	if (IS_ERR(data->reset_gpio))
+		return dev_err_probe(&client->dev, PTR_ERR(data->reset_gpio),
+				     "Failed to get reset GPIO\n");
+
+	/* Perform hardware reset if GPIO is provided */
+	if (data->reset_gpio) {
+		/* Perform reset sequence: low-high */
+		gpiod_set_value_cansleep(data->reset_gpio, 1);
+		fsleep(BH1750_RESET_DELAY_US);
+		gpiod_set_value_cansleep(data->reset_gpio, 0);
+		fsleep(BH1750_RESET_DELAY_US);
+
+		dev_dbg(&client->dev, "BH1750 reset completed via GPIO\n");
+	}
+
 	usec = data->chip_info->mtreg_to_usec * data->chip_info->mtreg_default;
 	ret = bh1750_change_int_time(data, usec);
 	if (ret < 0)
-- 
2.43.0