Input: exc3000 - add reset gpio support

Add basic support for an optional reset gpio.
Reviewed-by: NEnric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: NSebastian Reichel <sebastian.reichel@collabora.com>
Acked-by: NRob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200805160520.456570-4-sebastian.reichel@collabora.comSigned-off-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/devicetree/bindings/input/touchscreen/eeti,exc3000.yaml

@@ -22,6 +22,8 @@ properties:
     const: 0x2a
   interrupts:
     maxItems: 1
+  reset-gpios:
+    maxItems: 1
   touchscreen-size-x: true
   touchscreen-size-y: true
   touchscreen-inverted-x: true

drivers/input/touchscreen/exc3000.c

@@ -8,7 +8,9 @@
  */
 
 #include <linux/bitops.h>
+#include <linux/delay.h>
 #include <linux/device.h>
+#include <linux/gpio/consumer.h>
 #include <linux/i2c.h>
 #include <linux/input.h>
 #include <linux/input/mt.h>
@@ -30,6 +32,9 @@
 
 #define EXC3000_TIMEOUT_MS		100
 
+#define EXC3000_RESET_MS		10
+#define EXC3000_READY_MS		100
+
 static const struct i2c_device_id exc3000_id[];
 
 struct eeti_dev_info {
@@ -63,6 +68,7 @@ struct exc3000_data {
 	const struct eeti_dev_info *info;
 	struct input_dev *input;
 	struct touchscreen_properties prop;
+	struct gpio_desc *reset;
 	struct timer_list timer;
 	u8 buf[2 * EXC3000_LEN_FRAME];
 };
@@ -204,6 +210,17 @@ static int exc3000_probe(struct i2c_client *client)
 	}
 	timer_setup(&data->timer, exc3000_timer, 0);
 
+	data->reset = devm_gpiod_get_optional(&client->dev, "reset",
+					      GPIOD_OUT_HIGH);
+	if (IS_ERR(data->reset))
+		return PTR_ERR(data->reset);
+
+	if (data->reset) {
+		msleep(EXC3000_RESET_MS);
+		gpiod_set_value_cansleep(data->reset, 0);
+		msleep(EXC3000_READY_MS);
+	}
+
 	input = devm_input_allocate_device(&client->dev);
 	if (!input)
 		return -ENOMEM;