drivers: ssd1306: Support GPIO reset function

If dts has reset-gpios information, reset it.

Signed-off-by: Kwon Tae-young <tykwon@m2i.co.kr>

drivers/display/ssd1306.c

@@ -47,6 +47,7 @@ LOG_MODULE_REGISTER(ssd1306);
 #endif
 
 struct ssd1306_data {
+	struct device *reset;
 	struct device *i2c;
 	u8_t contrast;
 	u8_t scan_mode;
@@ -366,6 +367,12 @@ static int ssd1306_init_device(struct device *dev)
 		SSD1306_SET_NORMAL_DISPLAY,
 	};
 
+#ifdef DT_SOLOMON_SSD1306FB_0_RESET_GPIOS_CONTROLLER
+	gpio_pin_write(driver->reset, DT_SOLOMON_SSD1306FB_0_RESET_GPIOS_PIN, 0);
+	k_sleep(SSD1306_RESET_DELAY);
+	gpio_pin_write(driver->reset, DT_SOLOMON_SSD1306FB_0_RESET_GPIOS_PIN, 1);
+#endif
+
 	/* Turn display off */
 	if (ssd1306_reg_write(driver, SSD1306_CONTROL_LAST_BYTE_CMD,
 			      SSD1306_DISPLAY_OFF)) {
@@ -415,6 +422,18 @@ static int ssd1306_init(struct device *dev)
 		return -EINVAL;
 	}
 
+#ifdef DT_SOLOMON_SSD1306FB_0_RESET_GPIOS_CONTROLLER
+	driver->reset = device_get_binding(DT_SOLOMON_SSD1306FB_0_RESET_GPIOS_CONTROLLER);
+	if (driver->reset == NULL) {
+		LOG_ERR("Failed to get pointer to %s device!",
+			    DT_SOLOMON_SSD1306FB_0_RESET_GPIOS_CONTROLLER);
+		return -EINVAL;
+	}
+
+	gpio_pin_configure(driver->reset, DT_SOLOMON_SSD1306FB_0_RESET_GPIOS_PIN,
+			   GPIO_DIR_OUT);
+#endif
+
 	if (ssd1306_init_device(dev)) {
 		LOG_ERR("Failed to initialize device!");
 		return -EIO;

drivers/display/ssd1306_regs.h

@@ -106,4 +106,7 @@
 #define SSD1306_READ_MODIFY_WRITE_START		0xe0
 #define SSD1306_READ_MODIFY_WRITE_END		0xee
 
+/* time constants in ms */
+#define SSD1306_RESET_DELAY			1
+
 #endif