media: ov5647: Add support for PWDN GPIO.

Add support for an optional GPIO connected to PWDN on the sensor. This
allows the use of hardware standby mode where internal device clock
and circuit activities are halted.

Please note that power is off when PWDN is high.
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
Signed-off-by: Roman Kovalivskyi <roman.kovalivskyi@globallogic.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/i2c/ov5647.c

@@ -21,6 +21,7 @@
 
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/gpio/consumer.h>
 #include <linux/i2c.h>
 #include <linux/init.h>
 #include <linux/io.h>
@@ -35,6 +36,13 @@
 
 #define SENSOR_NAME "ov5647"
 
+/*
+ * From the datasheet, "20ms after PWDN goes low or 20ms after RESETB goes
+ * high if reset is inserted after PWDN goes high, host can access sensor's
+ * SCCB to initialize sensor."
+ */
+#define PWDN_ACTIVE_DELAY_MS	20
+
 #define MIPI_CTRL00_CLOCK_LANE_GATE		BIT(5)
 #define MIPI_CTRL00_BUS_IDLE			BIT(2)
 #define MIPI_CTRL00_CLOCK_LANE_DISABLE		BIT(0)
@@ -86,6 +94,7 @@ struct ov5647 {
 	unsigned int			height;
 	int				power_count;
 	struct clk			*xclk;
+	struct gpio_desc		*pwdn;
 };
 
 static inline struct ov5647 *to_state(struct v4l2_subdev *sd)
@@ -355,6 +364,11 @@ static int ov5647_sensor_power(struct v4l2_subdev *sd, int on)
 	if (on && !ov5647->power_count)	{
 		dev_dbg(&client->dev, "OV5647 power on\n");
 
+		if (ov5647->pwdn) {
+			gpiod_set_value_cansleep(ov5647->pwdn, 0);
+			msleep(PWDN_ACTIVE_DELAY_MS);
+		}
+
 		ret = clk_prepare_enable(ov5647->xclk);
 		if (ret < 0) {
 			dev_err(&client->dev, "clk prepare enable failed\n");
@@ -392,6 +406,8 @@ static int ov5647_sensor_power(struct v4l2_subdev *sd, int on)
 			dev_dbg(&client->dev, "soft stby failed\n");
 
 		clk_disable_unprepare(ov5647->xclk);
+
+		gpiod_set_value_cansleep(ov5647->pwdn, 1);
 	}
 
 	/* Update the power count. */
@@ -581,6 +597,14 @@ static int ov5647_probe(struct i2c_client *client)
 		return -EINVAL;
 	}
 
+	/* Request the power down GPIO asserted */
+	sensor->pwdn = devm_gpiod_get_optional(&client->dev, "pwdn",
+					       GPIOD_OUT_HIGH);
+	if (IS_ERR(sensor->pwdn)) {
+		dev_err(dev, "Failed to get 'pwdn' gpio\n");
+		return -EINVAL;
+	}
+
 	mutex_init(&sensor->lock);
 
 	sd = &sensor->sd;
@@ -594,7 +618,15 @@ static int ov5647_probe(struct i2c_client *client)
 	if (ret < 0)
 		goto mutex_remove;
 
+	if (sensor->pwdn) {
+		gpiod_set_value_cansleep(sensor->pwdn, 0);
+		msleep(PWDN_ACTIVE_DELAY_MS);
+	}
+
 	ret = ov5647_detect(sd);
+
+	gpiod_set_value_cansleep(sensor->pwdn, 1);
+
 	if (ret < 0)
 		goto error;