media: ov2740: Ensure proper reset sequence on probe()

Before this commit on probe() the driver would do:

reset=1                // from probe() calling gpiod_get(GPIOD_OUT_HIGH)
reset=0                // from resume()
msleep(20)             // from resume()

So if reset was 0 before getting the GPIO the reset line would only be
driven high for a very short time and sometimes there would be errors
reading the id register afterwards.

Add a msleep(20) after getting the reset line to ensure the sensor is
properly reset:

reset=1                // from probe() calling gpiod_get(GPIOD_OUT_HIGH)
msleep(20)             // from probe()
reset=0                // from resume()
msleep(20)             // from resume()

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Tested-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Author: jwrdegoede

drivers/media/i2c/ov2740.c

@@ -1333,9 +1333,16 @@ static int ov2740_probe(struct i2c_client *client)
 		return dev_err_probe(dev, ret, "failed to check HW configuration\n");
 
 	ov2740->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
-	if (IS_ERR(ov2740->reset_gpio))
+	if (IS_ERR(ov2740->reset_gpio)) {
 		return dev_err_probe(dev, PTR_ERR(ov2740->reset_gpio),
 				     "failed to get reset GPIO\n");
+	} else if (ov2740->reset_gpio) {
+		/*
+		 * Ensure reset is asserted for at least 20 ms before
+		 * ov2740_resume() deasserts it.
+		 */
+		msleep(20);
+	}
 
 	ov2740->clk = devm_clk_get_optional(dev, "clk");
 	if (IS_ERR(ov2740->clk))