[PATCH v3 2/3] leds: flash: rt8515: Support single-GPIO flash ICs with vin supply

[Rudraksha Gupta via B4 Relay <devnull+guptarud.gmail.com@kernel.org>]

From: Rudraksha Gupta <guptarud@gmail.com>

Extend the RT8515 driver to support flash ICs that use only a single
GPIO for both flash and torch modes (no separate ENT pin), with an
optional vin regulator that gates power to the flash IC.

When vin-supply is provided, the driver enables the regulator before
activating the LED and disables it when turning off.

Make ent-gpios optional and validate at probe time that exactly one of
ent-gpios or vin-supply is provided. When ent-gpios is absent, the
driver uses enf-gpios for both flash and torch brightness control.

Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Rudraksha Gupta <guptarud@gmail.com>
---
 drivers/leds/flash/leds-rt8515.c | 90 ++++++++++++++++++++++++++++++++--------
 1 file changed, 72 insertions(+), 18 deletions(-)

diff --git a/drivers/leds/flash/leds-rt8515.c b/drivers/leds/flash/leds-rt8515.c
index f6b439674c03..739cac8789c8 100644
--- a/drivers/leds/flash/leds-rt8515.c
+++ b/drivers/leds/flash/leds-rt8515.c
@@ -63,16 +63,44 @@ static struct rt8515 *to_rt8515(struct led_classdev_flash *fled)
 	return container_of(fled, struct rt8515, fled);
 }
 
-static void rt8515_gpio_led_off(struct rt8515 *rt)
+static int rt8515_led_off(struct rt8515 *rt)
 {
+	int ret;
+
 	gpiod_set_value(rt->enable_flash, 0);
-	gpiod_set_value(rt->enable_torch, 0);
+	if (rt->enable_torch)
+		gpiod_set_value(rt->enable_torch, 0);
+
+	/* Disable regulator */
+	ret = regulator_is_enabled(rt->reg);
+	if (ret < 0)
+		return ret;
+	if (ret > 0)
+		return regulator_disable(rt->reg);
+
+	return 0;
 }
 
-static void rt8515_gpio_brightness_commit(struct gpio_desc *gpiod,
-					  int brightness)
+static int rt8515_set_flash_brightness(struct rt8515 *rt,
+					 struct gpio_desc *gpiod,
+					 int brightness)
 {
 	int i;
+	int ret;
+
+	/*
+	 * Reset the IC to start brightness from zero,
+	 * then re-enable and pulse to the desired level.
+	 */
+	ret = rt8515_led_off(rt);
+	if (ret)
+		return ret;
+	/* IC needs time to reset its brightness counter */
+	usleep_range(100, 200);
+	/* Enable regulator */
+	ret = regulator_enable(rt->reg);
+	if (ret)
+		return ret;
 
 	/*
 	 * Toggling a GPIO line with a small delay increases the
@@ -84,31 +112,41 @@ static void rt8515_gpio_brightness_commit(struct gpio_desc *gpiod,
 		gpiod_set_value(gpiod, 1);
 		udelay(1);
 	}
+
+	return 0;
 }
 
 /* This is setting the torch light level */
-static int rt8515_led_brightness_set(struct led_classdev *led,
+static int rt8515_set_brightness(struct led_classdev *led,
 				     enum led_brightness brightness)
 {
 	struct led_classdev_flash *fled = lcdev_to_flcdev(led);
 	struct rt8515 *rt = to_rt8515(fled);
+	int ret = 0;
 
 	mutex_lock(&rt->lock);
 
 	if (brightness == LED_OFF) {
 		/* Off */
-		rt8515_gpio_led_off(rt);
+		ret = rt8515_led_off(rt);
+		if (ret)
+			goto out;
 	} else if (brightness < RT8515_TORCH_MAX) {
-		/* Step it up to movie mode brightness using the flash pin */
-		rt8515_gpio_brightness_commit(rt->enable_torch, brightness);
+		/* Step it up to movie mode brightness */
+		ret = rt8515_set_flash_brightness(rt, rt->enable_torch ?
+				rt->enable_torch : rt->enable_flash, brightness);
+		if (ret)
+			goto out;
 	} else {
 		/* Max torch brightness requested */
-		gpiod_set_value(rt->enable_torch, 1);
+		gpiod_set_value(rt->enable_torch ? rt->enable_torch :
+				rt->enable_flash, 1);
 	}
 
+out:
 	mutex_unlock(&rt->lock);
 
-	return 0;
+	return ret;
 }
 
 static int rt8515_led_flash_strobe_set(struct led_classdev_flash *fled,
@@ -117,27 +155,33 @@ static int rt8515_led_flash_strobe_set(struct led_classdev_flash *fled,
 	struct rt8515 *rt = to_rt8515(fled);
 	struct led_flash_setting *timeout = &fled->timeout;
 	int brightness = rt->flash_max_intensity;
+	int ret = 0;
 
 	mutex_lock(&rt->lock);
 
 	if (state) {
 		/* Enable LED flash mode and set brightness */
-		rt8515_gpio_brightness_commit(rt->enable_flash, brightness);
+		ret = rt8515_set_flash_brightness(rt, rt->enable_flash, brightness);
+		if (ret)
+			goto out;
 		/* Set timeout */
 		mod_timer(&rt->powerdown_timer,
 			  jiffies + usecs_to_jiffies(timeout->val));
 	} else {
 		timer_delete_sync(&rt->powerdown_timer);
 		/* Turn the LED off */
-		rt8515_gpio_led_off(rt);
+		ret = rt8515_led_off(rt);
+		if (ret)
+			goto out;
 	}
 
 	fled->led_cdev.brightness = LED_OFF;
 	/* After this the torch LED will be disabled */
 
+out:
 	mutex_unlock(&rt->lock);
 
-	return 0;
+	return ret;
 }
 
 static int rt8515_led_flash_strobe_get(struct led_classdev_flash *fled,
@@ -166,9 +210,12 @@ static const struct led_flash_ops rt8515_flash_ops = {
 static void rt8515_powerdown_timer(struct timer_list *t)
 {
 	struct rt8515 *rt = timer_container_of(rt, t, powerdown_timer);
+	int ret;
 
 	/* Turn the LED off */
-	rt8515_gpio_led_off(rt);
+	ret = rt8515_led_off(rt);
+	if (ret)
+		dev_err(rt->dev, "failed to turn off LED (%d)\n", ret);
 }
 
 static void rt8515_init_flash_timeout(struct rt8515 *rt)
@@ -298,12 +345,18 @@ static int rt8515_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, PTR_ERR(rt->enable_flash),
 				     "cannot get ENF (enable flash) GPIO\n");
 
-	/* ENT - Enable Torch line */
-	rt->enable_torch = devm_gpiod_get(dev, "ent", GPIOD_OUT_LOW);
+	/* ENT - Enable Torch line (optional for single-GPIO flash ICs) */
+	rt->enable_torch = devm_gpiod_get_optional(dev, "ent", GPIOD_OUT_LOW);
 	if (IS_ERR(rt->enable_torch))
 		return dev_err_probe(dev, PTR_ERR(rt->enable_torch),
 				     "cannot get ENT (enable torch) GPIO\n");
 
+	/* Optional VIN supply */
+	rt->reg = devm_regulator_get(dev, "vin");
+	if (IS_ERR(rt->reg))
+		return dev_err_probe(dev, PTR_ERR(rt->reg),
+				     "failed to get vin supply\n");
+
 	child = device_get_next_child_node(dev, NULL);
 	if (!child) {
 		dev_err(dev,
@@ -333,8 +386,9 @@ static int rt8515_probe(struct platform_device *pdev)
 
 	fled->ops = &rt8515_flash_ops;
 
-	led->max_brightness = rt->torch_max_intensity;
-	led->brightness_set_blocking = rt8515_led_brightness_set;
+	led->max_brightness = rt->enable_torch ?
+		rt->torch_max_intensity : rt->flash_max_intensity;
+	led->brightness_set_blocking = rt8515_set_brightness;
 	led->flags |= LED_CORE_SUSPENDRESUME | LED_DEV_CAP_FLASH;
 
 	mutex_init(&rt->lock);

-- 
2.53.0