[PATCH v3 0/3] Samsung Expressatt: Camera Flash

[PATCH v3 0/3] Samsung Expressatt: Camera Flash

[Rudraksha Gupta]

This small series adds camera flash to an existing similar mainline
driver and adds it to the Samsung Expressatt's DTS

// Tests

// # Navigate to LED
sudo su
cd /sys/class/leds/white:flash

// # Should stay at dim brightness
echo 1 > brightness
echo 1 > brightness
echo 1 > brightness
echo 1 > brightness
echo 0 > brightness           # LED_OFF

// # Max Brightness
echo 50 > brightness
echo 0 > brightness           # LED_OFF
echo 99 > brightness
echo 0 > brightness           # LED_OFF
echo 1000 > brightness
echo 0 > brightness           # LED_OFF
echo 100 > brightness
echo 0 > brightness           # LED_OFF

// # Should increase in brightness
for i in $(seq 1 16); do echo $i > brightness; sleep 1; done
echo 0 > brightness           # LED_OFF

// # Test flash strobe (rt8515_led_flash_strobe_set)
cat max_flash_timeout          # check max
echo 200000 > flash_timeout    # 200ms
echo 1 > flash_strobe          # strobe ON → brightness_commit + timer
cat flash_strobe               # should read 1, then 0 after timeout
sleep 1
cat flash_strobe               # should be 0 (timer fired)

// # Test manual strobe cancel
echo 1 > flash_strobe ; echo 0 > flash_strobe          # immediate off

// # Check regulator error handling
dmesg | tail -20                     # look for any "failed to turn off LED" msgs

Downstream reference:
Link: https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-12.0-YNG4N/drivers/leds/Makefile#L51
Link: https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-12.0-YNG4N/arch/arm/mach-msm/board-apexq-camera.c#L591

Signed-off-by: Rudraksha Gupta <guptarud@gmail.com>
---
Changes in v3:
- DTS:
    - Renamed and reordered nodes
- Driver:
    - Use regulator_is_enabled() instead of reg_enabled
    - remove ent xor vin check
    - remove rt->reg == -ENODEV check
    - rename functions to reflect what they do and added ret's
    - Fixed: LED was increasing in brightness when setting the same
        brightness multiple times
- Link to v2: https://lore.kernel.org/r/20260318-expressatt_camera_flash-v2-0-5c2b9a623dcb@gmail.com

Changes in v2:
- dt-bindings: Explain the hardware and not the driver
- **/*: Use vin-supply instead of unlock-gpio
- expressatt DTS: Reorder pinctrl-*
- expressatt DTS: Define rfs-ohms to a default (couldn't find
                  information about this)
- Link to v1: https://lore.kernel.org/r/20260306-expressatt_camera_flash-v1-0-b1996f7cdfdd@gmail.com

---
Rudraksha Gupta (3):
      dt-bindings: leds: rt8515: Support single-GPIO flash ICs with vin supply
      leds: flash: rt8515: Support single-GPIO flash ICs with vin supply
      ARM: dts: qcom: msm8960: expressatt: Add camera flash

 .../devicetree/bindings/leds/richtek,rt8515.yaml   | 34 +++++++-
 .../dts/qcom/qcom-msm8960-samsung-expressatt.dts   | 43 +++++++++++
 drivers/leds/flash/leds-rt8515.c                   | 90 +++++++++++++++++-----
 3 files changed, 148 insertions(+), 19 deletions(-)
---
base-commit: e9ec05addd1a067fc7cb218f20ecdc1b1b0898c0
change-id: 20260306-expressatt_camera_flash-13c15a7427aa
prerequisite-message-id: <20251205-expressatt-touchkey-v1-1-1444b927c9f3@gmail.com>
prerequisite-patch-id: 8de4de7909722ccaf385c4224f25a623eaa72c28

Best regards,
-- 
Rudraksha Gupta <guptarud@gmail.com>

[PATCH v3 1/3] dt-bindings: leds: rt8515: Support single-GPIO flash ICs with vin supply

[Rudraksha Gupta]

Some flash ICs use the same one-wire pulse-count protocol as the RT8515
but have only a single enable line for both flash and torch modes, plus
an optional input voltage supply (e.g. a GPIO-controlled fixed
regulator) that gates power to the chip.

Make ent-gpios optional and add a vin-supply property to support these
variants. Add a oneOf constraint requiring exactly one of ent-gpios or
vin-supply. Add a binding example showing the single-GPIO configuration
with an input supply.

Assisted-by: Claude:claude-opus-4.6
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Rudraksha Gupta <guptarud@gmail.com>
---
 .../devicetree/bindings/leds/richtek,rt8515.yaml   | 34 +++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/leds/richtek,rt8515.yaml b/Documentation/devicetree/bindings/leds/richtek,rt8515.yaml
index 0356371a6b01..ab3c5139132c 100644
--- a/Documentation/devicetree/bindings/leds/richtek,rt8515.yaml
+++ b/Documentation/devicetree/bindings/leds/richtek,rt8515.yaml
@@ -15,6 +15,10 @@ description: |
   current for each mode is defined in hardware using two resistors
   RFS and RTS.
 
+  Some flash ICs use the same one-wire pulse-count protocol but have
+  only a single enable line for both flash and torch modes. For these
+  single-channel variants, only enf-gpios is needed.
+
 properties:
   compatible:
     const: richtek,rt8515
@@ -26,6 +30,11 @@ properties:
   ent-gpios:
     maxItems: 1
     description: A connection to the 'ENT' (enable torch) pin.
+      Not present on single-channel flash ICs that use only one enable
+      line for both flash and torch modes.
+
+  vin-supply:
+    description: Optional input supply for the flash IC.
 
   richtek,rfs-ohms:
     minimum: 7680
@@ -81,10 +90,15 @@ properties:
 
 required:
   - compatible
-  - ent-gpios
   - enf-gpios
   - led
 
+oneOf:
+  - required:
+      - ent-gpios
+  - required:
+      - vin-supply
+
 additionalProperties: false
 
 examples:
@@ -108,4 +122,22 @@ examples:
         };
     };
 
+  - |
+    /* Single-channel flash IC with input supply */
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/leds/common.h>
+
+    led-controller {
+        compatible = "richtek,rt8515";
+        enf-gpios = <&tlmm 3 GPIO_ACTIVE_HIGH>;
+        vin-supply = <&flash_reg>;
+        richtek,rfs-ohms = <16000>;
+
+        led {
+            function = LED_FUNCTION_FLASH;
+            color = <LED_COLOR_ID_WHITE>;
+            flash-max-timeout-us = <250000>;
+        };
+    };
+
 ...

-- 
2.53.0

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

[Rudraksha Gupta]

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

[PATCH v3 3/3] ARM: dts: qcom: msm8960: expressatt: Add camera flash

[Rudraksha Gupta]

Add camera flash support for the Samsung Galaxy Express (expressatt).

The flash IC uses a one-wire pulse-count protocol on GPIO 3, powered
by a GPIO-controlled fixed regulator on PMIC MPP 4. The regulator is
modeled as a regulator-fixed node and supplied to the flash IC via
vin-supply.

Downstream references:
Link: https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-12.0-YNG4N/drivers/leds/Makefile#L51
Link: https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-12.0-YNG4N/arch/arm/mach-msm/board-apexq-camera.c#L591

Assisted-by: Claude:claude-opus-4.6
Reviewed-by: David Heidelberg <david@ixit.cz>
Signed-off-by: Rudraksha Gupta <guptarud@gmail.com>
---
 .../dts/qcom/qcom-msm8960-samsung-expressatt.dts   | 43 ++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts b/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts
index c4b98af6955d..35514fd53e3d 100644
--- a/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts
+++ b/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <dt-bindings/input/input.h>
+#include <dt-bindings/leds/common.h>
 #include <dt-bindings/reset/qcom,gcc-msm8960.h>
 
 #include "qcom-msm8960.dtsi"
@@ -61,6 +62,32 @@ touchkey_enable: touchkey-enable {
 		regulator-boot-on;
 	};
 
+	vreg_flash: regulator-flash {
+		compatible = "regulator-fixed";
+		regulator-name = "VREG_FLASH_3P3";
+		regulator-min-microvolt = <3300000>;
+		regulator-max-microvolt = <3300000>;
+		gpio = <&pm8921_mpps 4 GPIO_ACTIVE_HIGH>;
+		enable-active-high;
+		pinctrl-0 = <&flash_led_unlock>;
+		pinctrl-names = "default";
+	};
+
+	led-controller {
+		compatible = "richtek,rt8515";
+		enf-gpios = <&tlmm 3 GPIO_ACTIVE_HIGH>;
+		vin-supply = <&vreg_flash>;
+		richtek,rfs-ohms = <16000>;
+		pinctrl-0 = <&cam_flash_en>;
+		pinctrl-names = "default";
+
+		led {
+			function = LED_FUNCTION_FLASH;
+			color = <LED_COLOR_ID_WHITE>;
+			flash-max-timeout-us = <250000>;
+		};
+	};
+
 	i2c-gpio-touchkey {
 		compatible = "i2c-gpio";
 		#address-cells = <1>;
@@ -172,6 +199,13 @@ touchscreen@4a {
 };
 
 &tlmm {
+	cam_flash_en: cam-flash-en-state {
+		pins = "gpio3";
+		function = "gpio";
+		drive-strength = <16>;
+		bias-pull-down;
+	};
+
 	spi1_default: spi1-default-state {
 		mosi-pins {
 			pins = "gpio6";
@@ -572,3 +606,12 @@ magnetometer@2e {
 		/* TODO: Figure out Mount Matrix */
 	};
 };
+
+&pm8921_mpps {
+	flash_led_unlock: flash-led-unlock-state {
+		pins = "mpp4";
+		function = "digital";
+		output-low;
+		power-source = <PM8921_GPIO_S4>;
+	};
+};

-- 
2.53.0