video: hx8357: Make IM pins optional

The IM pins of the HX8357 controller are used to define the interface
used to feed pixel stream to the LCD panel.

Most of the time, these pins are directly routed to either the ground or
the VCC to set their values.

Remove the need to assign GPIOs to these pins when we are in such a case.
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/backlight/hx8357.c

@@ -76,6 +76,7 @@ struct hx8357_data {
 	unsigned		reset;
 	struct spi_device	*spi;
 	int			state;
+	bool			use_im_pins;
 };
 
 static u8 hx8357_seq_power[] = {
@@ -250,9 +251,11 @@ static int hx8357_lcd_init(struct lcd_device *lcdev)
 	 * Set the interface selection pins to SPI mode, with three
 	 * wires
 	 */
-	gpio_set_value_cansleep(lcd->im_pins[0], 1);
-	gpio_set_value_cansleep(lcd->im_pins[1], 0);
-	gpio_set_value_cansleep(lcd->im_pins[2], 1);
+	if (lcd->use_im_pins) {
+		gpio_set_value_cansleep(lcd->im_pins[0], 1);
+		gpio_set_value_cansleep(lcd->im_pins[1], 0);
+		gpio_set_value_cansleep(lcd->im_pins[2], 1);
+	}
 
 	/* Reset the screen */
 	gpio_set_value(lcd->reset, 1);
@@ -424,25 +427,32 @@ static int hx8357_probe(struct spi_device *spi)
 		return -EINVAL;
 	}
 
-	for (i = 0; i < HX8357_NUM_IM_PINS; i++) {
-		lcd->im_pins[i] = of_get_named_gpio(spi->dev.of_node,
-						"im-gpios", i);
-		if (lcd->im_pins[i] == -EPROBE_DEFER) {
-			dev_info(&spi->dev, "GPIO requested is not here yet, deferring the probe\n");
-			return -EPROBE_DEFER;
-		}
-		if (!gpio_is_valid(lcd->im_pins[i])) {
-			dev_err(&spi->dev, "Missing dt property: im-gpios\n");
-			return -EINVAL;
-		}
-
-		ret = devm_gpio_request_one(&spi->dev, lcd->im_pins[i],
-					GPIOF_OUT_INIT_LOW, "im_pins");
-		if (ret) {
-			dev_err(&spi->dev, "failed to request gpio %d: %d\n",
-				lcd->im_pins[i], ret);
-			return -EINVAL;
+	if (of_find_property(spi->dev.of_node, "im-gpios", NULL)) {
+		lcd->use_im_pins = 1;
+
+		for (i = 0; i < HX8357_NUM_IM_PINS; i++) {
+			lcd->im_pins[i] = of_get_named_gpio(spi->dev.of_node,
+							    "im-gpios", i);
+			if (lcd->im_pins[i] == -EPROBE_DEFER) {
+				dev_info(&spi->dev, "GPIO requested is not here yet, deferring the probe\n");
+				return -EPROBE_DEFER;
+			}
+			if (!gpio_is_valid(lcd->im_pins[i])) {
+				dev_err(&spi->dev, "Missing dt property: im-gpios\n");
+				return -EINVAL;
+			}
+
+			ret = devm_gpio_request_one(&spi->dev, lcd->im_pins[i],
+						    GPIOF_OUT_INIT_LOW,
+						    "im_pins");
+			if (ret) {
+				dev_err(&spi->dev, "failed to request gpio %d: %d\n",
+					lcd->im_pins[i], ret);
+				return -EINVAL;
+			}
 		}
+	} else {
+		lcd->use_im_pins = 0;
 	}
 
 	lcdev = lcd_device_register("mxsfb", &spi->dev, lcd, &hx8357_ops);