[media] mt9v032: Add reset and standby gpios

Add optional reset and standby gpios. The reset gpio is used to reset
the chip in power_on().

The standby gpio is not used currently. It is just unset, so the chip is
not in standby.

Signed-off-by: Markus Pargmann <[e-mail]>
Reviewed-by: Philipp Zabel <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Acked-by: Laurent Pinchart <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

Documentation/devicetree/bindings/media/i2c/mt9v032.txt

···
 
 - link-frequencies: List of allowed link frequencies in Hz. Each frequency is
 	expressed as a 64-bit big-endian integer.
+- reset-gpios: GPIO handle which is connected to the reset pin of the chip.
+- standby-gpios: GPIO handle which is connected to the standby pin of the chip.
 
 For further reading on port node refer to
 Documentation/devicetree/bindings/media/video-interfaces.txt.

drivers/media/i2c/mt9v032.c

···
 
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/gpio/consumer.h>
 #include <linux/i2c.h>
 #include <linux/log2.h>
 #include <linux/mutex.h>
···
 
 	struct regmap *regmap;
 	struct clk *clk;
+	struct gpio_desc *reset_gpio;
+	struct gpio_desc *standby_gpio;
 
 	struct mt9v032_platform_data *pdata;
 	const struct mt9v032_model_info *model;
···
 	struct regmap *map = mt9v032->regmap;
 	int ret;
 
+	if (mt9v032->reset_gpio)
+		gpiod_set_value_cansleep(mt9v032->reset_gpio, 1);
+
 	ret = clk_set_rate(mt9v032->clk, mt9v032->sysclk);
 	if (ret < 0)
 		return ret;
 
+	/* System clock has to be enabled before releasing the reset */
 	ret = clk_prepare_enable(mt9v032->clk);
 	if (ret)
 		return ret;
 
 	udelay(1);
+
+	if (mt9v032->reset_gpio) {
+		gpiod_set_value_cansleep(mt9v032->reset_gpio, 0);
+
+		/* After releasing reset we need to wait 10 clock cycles
+		 * before accessing the sensor over I2C. As the minimum SYSCLK
+		 * frequency is 13MHz, waiting 1µs will be enough in the worst
+		 * case.
+		 */
+		udelay(1);
+	}
 
 	/* Reset the chip and stop data read out */
 	ret = regmap_write(map, MT9V032_RESET, 1);
···
 	mt9v032->clk = devm_clk_get(&client->dev, NULL);
 	if (IS_ERR(mt9v032->clk))
 		return PTR_ERR(mt9v032->clk);
+
+	mt9v032->reset_gpio = devm_gpiod_get_optional(&client->dev, "reset",
+						      GPIOD_OUT_HIGH);
+	if (IS_ERR(mt9v032->reset_gpio))
+		return PTR_ERR(mt9v032->reset_gpio);
+
+	mt9v032->standby_gpio = devm_gpiod_get_optional(&client->dev, "standby",
+							GPIOD_OUT_LOW);
+	if (IS_ERR(mt9v032->standby_gpio))
+		return PTR_ERR(mt9v032->standby_gpio);
 
 	mutex_init(&mt9v032->power_lock);
 	mt9v032->pdata = pdata;