[PATCH v3 0/4] backlight: add new max25014 backlight driver

[PATCH v3 0/4] backlight: add new max25014 backlight driver

[Maud Spierings via B4 Relay]

The Maxim MAX25014 is an automotive grade backlight driver IC. Its
datasheet can be found at [1].

With its integrated boost controller, it can power 4 channels (led
strings) and has a number of different modes using pwm and or i2c.
Currently implemented is only i2c control.

link: https://www.analog.com/media/en/technical-documentation/data-sheets/MAX25014.pdf [1]

Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
---
Changes in v3:
- fixed commit message type intgrated -> integrated
- added maximum and description to maxim,iset-property
- dropped unused labels and pinctrl in bindings example
- put the compatible first in the bindings example and dts
- removed brackets around defines
- removed the leftover pdata struct field
- removed the initial_brightness struct field
- Link to v2: https://lore.kernel.org/r/20250819-max25014-v2-0-5fd7aeb141ea@gocontroll.com

Changes in v2:
- Remove leftover unused property from the bindings example
- Complete the bindings example with all properties
- Remove some double info from the maxim,iset property
- Remove platform_data header, fold its data into the max25014 struct
- Don't force defines to be unsigned
- Remove stray struct max25014 declaration
- Remove chipname and device from the max25014 struct
- Inline the max25014_backlight_register() and strings_mask() functions
- Remove CONFIG_OF ifdef
- Link to v1: https://lore.kernel.org/r/20250725-max25014-v1-0-0e8cce92078e@gocontroll.com

---
Maud Spierings (4):
      dt-bindings: backlight: Add max25014 bindings
      backlight: add max25014atg backlight
      arm64: dts: freescale: moduline-display-av101hdt-a10: add backlight
      arm64: dts: freescale: moduline-display-av123z7m-n17: add backlight

 .../bindings/leds/backlight/maxim,max25014.yaml    |  81 +++++
 MAINTAINERS                                        |   6 +
 ...x8p-ml81-moduline-display-106-av101hdt-a10.dtso |  21 ++
 ...x8p-ml81-moduline-display-106-av123z7m-n17.dtso |  19 +-
 drivers/video/backlight/Kconfig                    |   7 +
 drivers/video/backlight/Makefile                   |   1 +
 drivers/video/backlight/max25014.c                 | 394 +++++++++++++++++++++
 7 files changed, 528 insertions(+), 1 deletion(-)
---
base-commit: 8f21d9da46702c4d6951ba60ca8a05f42870fe8f
change-id: 20250626-max25014-4207591e1af5

Best regards,
-- 
Maud Spierings <maudspierings@gocontroll.com>

[PATCH v3 1/4] dt-bindings: backlight: Add max25014 bindings

[Maud Spierings via B4 Relay]

From: Maud Spierings <maudspierings@gocontroll.com>

The Maxim MAX25014 is a 4-channel automotive grade backlight driver IC
with integrated boost controller.

Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
---
 .../bindings/leds/backlight/maxim,max25014.yaml    | 81 ++++++++++++++++++++++
 MAINTAINERS                                        |  5 ++
 2 files changed, 86 insertions(+)

diff --git a/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml b/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
new file mode 100644
index 0000000000000000000000000000000000000000..e113a2ad16aa74f982b9c2ea80578aed2d9424fe
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
@@ -0,0 +1,81 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/backlight/maxim,max25014.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Maxim max25014 backlight controller
+
+maintainers:
+  - Maud Spierings <maudspierings@gocontroll.com>
+
+allOf:
+  - $ref: common.yaml#
+
+properties:
+  compatible:
+    enum:
+      - maxim,max25014
+
+  reg:
+    maxItems: 1
+
+  enable-gpios:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  power-supply:
+    description: Regulator which controls the boost converter input rail.
+
+  pwms:
+    maxItems: 1
+
+  maxim,iset:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    maximum: 15
+    default: 11
+    description:
+      Value of the ISET register field. This controls the current scale of the
+      outputs, a higher number means more current.
+
+  maxim,strings:
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    description:
+      A 4-bit bitfield that describes which led strings to turn on.
+    minItems: 4
+    maxItems: 4
+    items:
+      maximum: 1
+
+required:
+  - compatible
+  - reg
+  - maxim,strings
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        backlight@6f {
+            compatible = "maxim,max25014";
+            reg = <0x6f>;
+            default-brightness = <50>;
+            enable-gpios = <&gpio1 4 GPIO_ACTIVE_HIGH>;
+            interrupt-parent = <&gpio1>;
+            interrupts = <2 IRQ_TYPE_EDGE_FALLING>;
+            power-supply = <&reg_backlight>;
+            pwms = <&pwm1>;
+            maxim,iset = <7>;
+            maxim,strings = <1 1 1 1>;
+        };
+    };
+
diff --git a/MAINTAINERS b/MAINTAINERS
index 7b7396ed28a700a2aab318553ce8ba1788312bff..5a592eefbe7562734aada05ab9e3aea8cee010e7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15069,6 +15069,11 @@ F:	Documentation/userspace-api/media/drivers/max2175.rst
 F:	drivers/media/i2c/max2175*
 F:	include/uapi/linux/max2175.h
 
+MAX25014 BACKLIGHT DRIVER
+M:	Maud Spierings <maudspierings@gocontroll.com>
+S:	Maintained
+F:	Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
+
 MAX31335 RTC DRIVER
 M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
 L:	linux-rtc@vger.kernel.org

-- 
2.51.0

[PATCH v3 2/4] backlight: add max25014atg backlight

[Maud Spierings via B4 Relay]

From: Maud Spierings <maudspierings@gocontroll.com>

The Maxim MAX25014 is a 4-channel automotive grade backlight driver IC
with integrated boost controller.

Signed-off-by: Maud Spierings maudspierings@gocontroll.com
---
 MAINTAINERS                        |   1 +
 drivers/video/backlight/Kconfig    |   7 +
 drivers/video/backlight/Makefile   |   1 +
 drivers/video/backlight/max25014.c | 394 +++++++++++++++++++++++++++++++++++++
 4 files changed, 403 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 5a592eefbe7562734aada05ab9e3aea8cee010e7..f73d0b94922fe9d7e691a5578a72af41b998a365 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15073,6 +15073,7 @@ MAX25014 BACKLIGHT DRIVER
 M:	Maud Spierings <maudspierings@gocontroll.com>
 S:	Maintained
 F:	Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
+F:	drivers/video/backlight/max25014.c
 
 MAX31335 RTC DRIVER
 M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index d9374d208ceebbf8b3c27976e9cb4d725939b942..d3bb6ccd41853d940f24c6ab8135e4b9b9ebefd7 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -262,6 +262,13 @@ config BACKLIGHT_DA9052
 	help
 	  Enable the Backlight Driver for DA9052-BC and DA9053-AA/Bx PMICs.
 
+config BACKLIGHT_MAX25014
+	tristate "Backlight driver for the Maxim MAX25014 chip"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  If you are using a MAX25014 chip as a backlight driver say Y to enable it.
+
 config BACKLIGHT_MAX8925
 	tristate "Backlight driver for MAX8925"
 	depends on MFD_MAX8925
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index dfbb169bf6ea215704859f633b6c4a887f4ebacd..1170d9ec40b8dbd52aeec1dade1cd2d2b56af466 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -45,6 +45,7 @@ obj-$(CONFIG_BACKLIGHT_LOCOMO)		+= locomolcd.o
 obj-$(CONFIG_BACKLIGHT_LP855X)		+= lp855x_bl.o
 obj-$(CONFIG_BACKLIGHT_LP8788)		+= lp8788_bl.o
 obj-$(CONFIG_BACKLIGHT_LV5207LP)	+= lv5207lp.o
+obj-$(CONFIG_BACKLIGHT_MAX25014)	+= max25014.o
 obj-$(CONFIG_BACKLIGHT_MAX8925)		+= max8925_bl.o
 obj-$(CONFIG_BACKLIGHT_MP3309C)		+= mp3309c.o
 obj-$(CONFIG_BACKLIGHT_MT6370)		+= mt6370-backlight.o
diff --git a/drivers/video/backlight/max25014.c b/drivers/video/backlight/max25014.c
new file mode 100644
index 0000000000000000000000000000000000000000..f4ca79dfc39ccb04702e6114c35a5863f80b8853
--- /dev/null
+++ b/drivers/video/backlight/max25014.c
@@ -0,0 +1,394 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Backlight driver for Maxim MAX25014
+ *
+ * Copyright (C) 2025 GOcontroll B.V.
+ * Author: Maud Spierings <maudspierings@gocontroll.com>
+ */
+
+#include <linux/backlight.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#define MAX25014_ISET_DEFAULT_100 11
+#define MAX_BRIGHTNESS            100
+#define MIN_BRIGHTNESS            0
+#define TON_MAX                   130720 /* @153Hz */
+#define TON_STEP                  1307 /* @153Hz */
+#define TON_MIN                   0
+
+#define MAX25014_DEV_ID           0x00
+#define MAX25014_REV_ID           0x01
+#define MAX25014_ISET             0x02
+#define MAX25014_IMODE            0x03
+#define MAX25014_TON1H            0x04
+#define MAX25014_TON1L            0x05
+#define MAX25014_TON2H            0x06
+#define MAX25014_TON2L            0x07
+#define MAX25014_TON3H            0x08
+#define MAX25014_TON3L            0x09
+#define MAX25014_TON4H            0x0A
+#define MAX25014_TON4L            0x0B
+#define MAX25014_TON_1_4_LSB      0x0C
+#define MAX25014_SETTING          0x12
+#define MAX25014_DISABLE          0x13
+#define MAX25014_BSTMON           0x14
+#define MAX25014_IOUT1            0x15
+#define MAX25014_IOUT2            0x16
+#define MAX25014_IOUT3            0x17
+#define MAX25014_IOUT4            0x18
+#define MAX25014_OPEN             0x1B
+#define MAX25014_SHORT_GND        0x1C
+#define MAX25014_SHORT_LED        0x1D
+#define MAX25014_MASK             0x1E
+#define MAX25014_DIAG             0x1F
+
+#define MAX25014_IMODE_HDIM       BIT(2)
+#define MAX25014_ISET_ENABLE      BIT(5)
+#define MAX25014_ISET_PSEN        BIT(4)
+#define MAX25014_DIAG_HW_RST      BIT(2)
+#define MAX25014_SETTING_FPWM     GENMASK(6, 4)
+
+struct max25014 {
+	struct i2c_client *client;
+	struct backlight_device *bl;
+	struct regmap *regmap;
+	struct gpio_desc *enable;
+	struct regulator *vin; /* regulator for boost converter Vin rail */
+	uint32_t iset;
+	uint8_t strings_mask;
+};
+
+static const struct regmap_config max25014_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = MAX25014_DIAG,
+};
+
+/**
+ * @brief control the brightness with i2c registers
+ *
+ * @param regmap trivial
+ * @param brt brightness
+ * @return int
+ */
+static int max25014_register_control(struct regmap *regmap, uint32_t brt)
+{
+	uint32_t reg = TON_STEP * brt;
+	int ret;
+	/*
+	 * 18 bit number lowest, 2 bits in first register,
+	 * next lowest 8 in the L register, next 8 in the H register
+	 * Seemingly setting the strength of only one string controls all of
+	 * them, individual settings don't affect the outcome.
+	 */
+
+	ret = regmap_write(regmap, MAX25014_TON_1_4_LSB, reg & 0b00000011);
+	if (ret != 0)
+		return ret;
+	ret = regmap_write(regmap, MAX25014_TON1L, (reg >> 2) & 0b11111111);
+	if (ret != 0)
+		return ret;
+	return regmap_write(regmap, MAX25014_TON1H, (reg >> 10) & 0b11111111);
+}
+
+static int max25014_check_errors(struct max25014 *maxim)
+{
+	uint8_t i;
+	int ret;
+	uint32_t val;
+
+	ret = regmap_read(maxim->regmap, MAX25014_OPEN, &val);
+	if (ret != 0)
+		return ret;
+	if (val > 0) {
+		dev_err(&maxim->client->dev, "Open led strings detected on:\n");
+		for (i = 0; i < 4; i++) {
+			if (val & 1 << i)
+				dev_err(&maxim->client->dev, "string %d\n", i + 1);
+		}
+		return -EIO;
+	}
+
+	ret = regmap_read(maxim->regmap, MAX25014_SHORT_GND, &val);
+	if (ret != 0)
+		return ret;
+	if (val > 0) {
+		dev_err(&maxim->client->dev, "Short to ground detected on:\n");
+		for (i = 0; i < 4; i++) {
+			if (val & 1 << i)
+				dev_err(&maxim->client->dev, "string %d\n", i + 1);
+		}
+		return -EIO;
+	}
+
+	ret = regmap_read(maxim->regmap, MAX25014_SHORT_GND, &val);
+	if (ret != 0)
+		return ret;
+	if (val > 0) {
+		dev_err(&maxim->client->dev, "Shorted led detected on:\n");
+		for (i = 0; i < 4; i++) {
+			if (val & 1 << i)
+				dev_err(&maxim->client->dev, "string %d\n", i + 1);
+		}
+		return -EIO;
+	}
+
+	ret = regmap_read(maxim->regmap, MAX25014_DIAG, &val);
+	if (ret != 0)
+		return ret;
+	/*
+	 * The HW_RST bit always starts at 1 after power up.
+	 * It is reset on first read, does not indicate an error.
+	 */
+	if (val > 0 && val != MAX25014_DIAG_HW_RST) {
+		if (val & 0b1)
+			dev_err(&maxim->client->dev, "Overtemperature shutdown\n");
+		if (val & 0b10)
+			dev_warn(&maxim->client->dev,
+				 "Chip is getting too hot (>125C)\n");
+		if (val & 0b1000)
+			dev_err(&maxim->client->dev, "Boost converter overvoltage\n");
+		if (val & 0b10000)
+			dev_err(&maxim->client->dev, "Boost converter undervoltage\n");
+		if (val & 0b100000)
+			dev_err(&maxim->client->dev, "IREF out of range\n");
+		return -EIO;
+	}
+	return 0;
+}
+
+/*
+ * 1. disable unused strings
+ * 2. set dim mode
+ * 3. set initial brightness
+ * 4. set setting register
+ * 5. enable the backlight
+ */
+static int max25014_configure(struct max25014 *maxim, uint32_t initial_brightness)
+{
+	int ret;
+	uint32_t val;
+
+	ret = regmap_write(maxim->regmap, MAX25014_DISABLE,
+			   maxim->strings_mask);
+	if (ret != 0)
+		return ret;
+
+	ret = regmap_write(maxim->regmap, MAX25014_IMODE, MAX25014_IMODE_HDIM);
+	if (ret != 0)
+		return ret;
+
+	max25014_register_control(maxim->regmap,
+				  initial_brightness);
+
+	ret = regmap_read(maxim->regmap, MAX25014_SETTING, &val);
+	if (ret != 0)
+		return ret;
+
+	ret = regmap_write(
+		maxim->regmap, MAX25014_SETTING,
+		val & ~MAX25014_SETTING_FPWM);
+	if (ret != 0)
+		return ret;
+
+	ret = regmap_write(maxim->regmap, MAX25014_ISET,
+			   maxim->iset | MAX25014_ISET_ENABLE | MAX25014_ISET_PSEN);
+	return ret;
+}
+
+static int max25014_update_status(struct backlight_device *bl_dev)
+{
+	struct max25014 *maxim = bl_get_data(bl_dev);
+
+	if (bl_dev->props.state & BL_CORE_SUSPENDED)
+		bl_dev->props.brightness = 0;
+
+	return max25014_register_control(maxim->regmap, bl_dev->props.brightness);
+}
+
+static const struct backlight_ops max25014_bl_ops = {
+	.options = BL_CORE_SUSPENDRESUME,
+	.update_status = max25014_update_status,
+};
+
+static int max25014_parse_dt(struct max25014 *maxim, uint32_t *initial_brightness)
+{
+	struct device *dev = &maxim->client->dev;
+	struct device_node *node = dev->of_node;
+	uint32_t strings[4];
+	int res, i;
+
+	if (!node) {
+		dev_err(dev, "no platform data\n");
+		return -EINVAL;
+	}
+
+	res = of_property_count_u32_elems(node, "maxim,strings");
+	if (res == 4) {
+		of_property_read_u32_array(node, "maxim,strings", strings, 4);
+	} else {
+		dev_err(dev, "strings property not correctly defined\n");
+		return -EINVAL;
+	}
+
+	for (i = 0; i < 4; i++) {
+		if (strings[i] == 0)
+			maxim->strings_mask |= 1 << i;
+	}
+
+	*initial_brightness = 50U;
+	of_property_read_u32(node, "default-brightness", initial_brightness);
+	maxim->iset = MAX25014_ISET_DEFAULT_100;
+	of_property_read_u32(node, "maxim,iset", &maxim->iset);
+
+	if (maxim->iset < 0 || maxim->iset > 15) {
+		dev_err(dev,
+			"Invalid iset, should be a value from 0-15, entered was %d\n",
+			maxim->iset);
+		return -EINVAL;
+	}
+
+	if (*initial_brightness < 0 || *initial_brightness > 100) {
+		dev_err(dev,
+			"Invalid initial brightness, should be a value from 0-100, entered was %d\n",
+			*initial_brightness);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int max25014_probe(struct i2c_client *cl)
+{
+	struct backlight_device *bl;
+	const struct i2c_device_id *id = i2c_client_get_device_id(cl);
+	struct max25014 *maxim;
+	struct backlight_properties props;
+	int ret;
+	uint32_t initial_brightness;
+
+	maxim = devm_kzalloc(&cl->dev, sizeof(struct max25014), GFP_KERNEL);
+	if (!maxim)
+		return -ENOMEM;
+
+	maxim->client = cl;
+
+	ret = max25014_parse_dt(maxim, &initial_brightness);
+	if (ret < 0)
+		return ret;
+
+	maxim->vin = devm_regulator_get(&maxim->client->dev, "power");
+	if (IS_ERR(maxim->vin)) {
+		if (PTR_ERR(maxim->vin) == -EPROBE_DEFER)
+			return -EPROBE_DEFER;
+		maxim->vin = NULL;
+	}
+
+	if (maxim->vin) {
+		ret = regulator_enable(maxim->vin);
+		if (ret < 0) {
+			dev_err(&maxim->client->dev, "failed to enable Vin: %d\n", ret);
+			return ret;
+		}
+	}
+
+	maxim->enable =
+		devm_gpiod_get_optional(&maxim->client->dev, "enable", GPIOD_ASIS);
+	if (IS_ERR(maxim->enable)) {
+		ret = PTR_ERR(maxim->enable);
+		dev_err(&maxim->client->dev, "failed to get enable gpio: %d\n", ret);
+		goto disable_vin;
+	}
+
+	if (maxim->enable) {
+		gpiod_set_value_cansleep(maxim->enable, 1);
+
+		/* Datasheet Electrical Characteristics tSTARTUP 2ms */
+		usleep_range(2000, 2500);
+	}
+
+	maxim->regmap = devm_regmap_init_i2c(cl, &max25014_regmap_config);
+	if (IS_ERR(maxim->regmap)) {
+		ret = PTR_ERR(maxim->regmap);
+		dev_err(&maxim->client->dev, "failed to initialize the i2c regmap: %d\n", ret);
+		goto disable_full;
+	}
+
+	i2c_set_clientdata(cl, maxim);
+
+	ret = max25014_check_errors(maxim);
+	if (ret) { /* error is already reported in the above function */
+		goto disable_full;
+	}
+
+	ret = max25014_configure(maxim, initial_brightness);
+	if (ret) {
+		dev_err(&maxim->client->dev, "device config err: %d", ret);
+		goto disable_full;
+	}
+
+	memset(&props, 0, sizeof(props));
+	props.type = BACKLIGHT_PLATFORM;
+	props.max_brightness = MAX_BRIGHTNESS;
+
+	props.brightness = initial_brightness;
+
+	bl = devm_backlight_device_register(&maxim->client->dev, id->name, &maxim->client->dev,
+					    maxim, &max25014_bl_ops, &props);
+	if (IS_ERR(bl))
+		return PTR_ERR(bl);
+
+	maxim->bl = bl;
+
+	return 0;
+
+disable_full:
+	if (maxim->enable)
+		gpiod_set_value_cansleep(maxim->enable, 0);
+disable_vin:
+	if (maxim->vin)
+		regulator_disable(maxim->vin);
+	return ret;
+}
+
+static void max25014_remove(struct i2c_client *cl)
+{
+	struct max25014 *maxim = i2c_get_clientdata(cl);
+
+	maxim->bl->props.brightness = 0;
+	max25014_update_status(maxim->bl);
+	if (maxim->enable)
+		gpiod_set_value_cansleep(maxim->enable, 0);
+	if (maxim->vin)
+		regulator_disable(maxim->vin);
+}
+
+static const struct of_device_id max25014_dt_ids[] = {
+	{ .compatible = "maxim,max25014", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max25014_dt_ids);
+
+static const struct i2c_device_id max25014_ids[] = {
+	{ "max25014" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max25014_ids);
+
+static struct i2c_driver max25014_driver = {
+	.driver = {
+		.name = KBUILD_MODNAME,
+		.of_match_table = of_match_ptr(max25014_dt_ids),
+	},
+	.probe = max25014_probe,
+	.remove = max25014_remove,
+	.id_table = max25014_ids,
+};
+module_i2c_driver(max25014_driver);
+
+MODULE_DESCRIPTION("Maxim MAX25014 backlight driver");
+MODULE_AUTHOR("Maud Spierings <maudspierings@gocontroll.com>");
+MODULE_LICENSE("GPL");

-- 
2.51.0

[PATCH v3 3/4] arm64: dts: freescale: moduline-display-av101hdt-a10: add backlight

[Maud Spierings via B4 Relay]

From: Maud Spierings <maudspierings@gocontroll.com>

Add the missing backlight driver.

Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
---
 ...tx8p-ml81-moduline-display-106-av101hdt-a10.dtso | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/arch/arm64/boot/dts/freescale/imx8mp-tx8p-ml81-moduline-display-106-av101hdt-a10.dtso b/arch/arm64/boot/dts/freescale/imx8mp-tx8p-ml81-moduline-display-106-av101hdt-a10.dtso
index e3965caca6be42a17aa89b77bd5b919382c84151..3d0983a3ab5463196de8cefb863bde74426b735d 100644
--- a/arch/arm64/boot/dts/freescale/imx8mp-tx8p-ml81-moduline-display-106-av101hdt-a10.dtso
+++ b/arch/arm64/boot/dts/freescale/imx8mp-tx8p-ml81-moduline-display-106-av101hdt-a10.dtso
@@ -17,6 +17,7 @@
 
 	panel {
 		compatible = "boe,av101hdt-a10";
+		backlight = <&backlight>;
 		enable-gpios = <&gpio1 7 GPIO_ACTIVE_HIGH>;
 		pinctrl-0 = <&pinctrl_panel>;
 		pinctrl-names = "default";
@@ -40,7 +41,27 @@ reg_vbus: regulator-vbus {
 	};
 };
 
+&i2c4 {
+	backlight: backlight@6f {
+		compatible = "maxim,max25014";
+		reg = <0x6f>;
+		default-brightness = <50>;
+		enable-gpios = <&gpio1 4 GPIO_ACTIVE_HIGH>;
+		pinctrl-names = "default";
+		pinctrl-0 = <&pinctrl_backlight>;
+		maxim,iset = <7>;
+		maxim,strings = <1 1 1 0>;
+	};
+};
+
 &iomuxc {
+	pinctrl_backlight: backlightgrp {
+		fsl,pins = <
+			MX8MP_IOMUXC_GPIO1_IO04__GPIO1_IO04
+				(MX8MP_PULL_UP | MX8MP_PULL_ENABLE)
+		>;
+	};
+
 	pinctrl_panel: panelgrp {
 		fsl,pins = <
 			MX8MP_IOMUXC_GPIO1_IO07__GPIO1_IO07

-- 
2.51.0

[PATCH v3 4/4] arm64: dts: freescale: moduline-display-av123z7m-n17: add backlight

[Maud Spierings via B4 Relay]

From: Maud Spierings <maudspierings@gocontroll.com>

Add the missing backlight.

Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
---
 ...p-tx8p-ml81-moduline-display-106-av123z7m-n17.dtso | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/freescale/imx8mp-tx8p-ml81-moduline-display-106-av123z7m-n17.dtso b/arch/arm64/boot/dts/freescale/imx8mp-tx8p-ml81-moduline-display-106-av123z7m-n17.dtso
index 3eb665ce9d5d2a1c742ffb4feca046e406e29956..0b969c8c04db1c86b2a90c5f5ef91e494e5de7a6 100644
--- a/arch/arm64/boot/dts/freescale/imx8mp-tx8p-ml81-moduline-display-106-av123z7m-n17.dtso
+++ b/arch/arm64/boot/dts/freescale/imx8mp-tx8p-ml81-moduline-display-106-av123z7m-n17.dtso
@@ -16,6 +16,7 @@
 
 	panel {
 		compatible = "boe,av123z7m-n17";
+		backlight = <&backlight>;
 		enable-gpios = <&gpio1 7 GPIO_ACTIVE_HIGH>;
 		pinctrl-0 = <&pinctrl_panel>;
 		pinctrl-names = "default";
@@ -91,10 +92,26 @@ lvds1_out: endpoint {
 		};
 	};
 
-	/* max25014 @ 0x6f */
+	backlight: backlight@6f {
+		compatible = "maxim,max25014";
+		reg = <0x6f>;
+		default-brightness = <50>;
+		enable-gpios = <&gpio1 4 GPIO_ACTIVE_HIGH>;
+		pinctrl-names = "default";
+		pinctrl-0 = <&pinctrl_backlight>;
+		maxim,iset = <7>;
+		maxim,strings = <1 1 1 1>;
+	};
 };
 
 &iomuxc {
+	pinctrl_backlight: backlightgrp {
+		fsl,pins = <
+			MX8MP_IOMUXC_GPIO1_IO04__GPIO1_IO04
+				(MX8MP_PULL_UP | MX8MP_PULL_ENABLE)
+		>;
+	};
+
 	pinctrl_lvds_bridge: lvdsbridgegrp {
 		fsl,pins = <
 			MX8MP_IOMUXC_SAI1_TXD2__GPIO4_IO14

-- 
2.51.0

Re: [PATCH v3 2/4] backlight: add max25014atg backlight

[Maud Spierings]

On 9/11/25 09:53, Maud Spierings via B4 Relay wrote:
> From: Maud Spierings <maudspierings@gocontroll.com>
> 
> The Maxim MAX25014 is a 4-channel automotive grade backlight driver IC
> with integrated boost controller.
> 
> Signed-off-by: Maud Spierings maudspierings@gocontroll.com

b4 has been complaining for a bit but I couldn't figure out why, I just 
figured it out. The SoB tag is malformed somehow, the <> around the 
email address is missing. Will fix this in the next version.

Kind regards,
Maud

Re: [PATCH v3 1/4] dt-bindings: backlight: Add max25014 bindingsy

[Frank Li]

On Thu, Sep 11, 2025 at 09:53:18AM +0200, Maud Spierings via B4 Relay wrote:
> From: Maud Spierings <maudspierings@gocontroll.com>
>
> The Maxim MAX25014 is a 4-channel automotive grade backlight driver IC
> with integrated boost controller.
>
> Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
> ---
>  .../bindings/leds/backlight/maxim,max25014.yaml    | 81 ++++++++++++++++++++++
>  MAINTAINERS                                        |  5 ++
>  2 files changed, 86 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml b/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
> new file mode 100644
> index 0000000000000000000000000000000000000000..e113a2ad16aa74f982b9c2ea80578aed2d9424fe
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
> @@ -0,0 +1,81 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/leds/backlight/maxim,max25014.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Maxim max25014 backlight controller
> +
> +maintainers:
> +  - Maud Spierings <maudspierings@gocontroll.com>
> +
> +allOf:
> +  - $ref: common.yaml#
> +
> +properties:
> +  compatible:
> +    enum:
> +      - maxim,max25014
> +
> +  reg:
> +    maxItems: 1
> +
> +  enable-gpios:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  power-supply:
> +    description: Regulator which controls the boost converter input rail.
> +
> +  pwms:
> +    maxItems: 1
> +
> +  maxim,iset:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    maximum: 15
> +    default: 11
> +    description:
> +      Value of the ISET register field. This controls the current scale of the
> +      outputs, a higher number means more current.

Use standard unit. Do not use register value directly.

> +
> +  maxim,strings:
> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +    description:
> +      A 4-bit bitfield that describes which led strings to turn on.
> +    minItems: 4
> +    maxItems: 4
> +    items:
> +      maximum: 1

led should have standard interface.

check  Documentation/devicetree/bindings/leds/common.yaml

Frank

> +
> +required:
> +  - compatible
> +  - reg
> +  - maxim,strings
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    #include <dt-bindings/interrupt-controller/irq.h>
> +
> +    i2c {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        backlight@6f {
> +            compatible = "maxim,max25014";
> +            reg = <0x6f>;
> +            default-brightness = <50>;
> +            enable-gpios = <&gpio1 4 GPIO_ACTIVE_HIGH>;
> +            interrupt-parent = <&gpio1>;
> +            interrupts = <2 IRQ_TYPE_EDGE_FALLING>;
> +            power-supply = <&reg_backlight>;
> +            pwms = <&pwm1>;
> +            maxim,iset = <7>;
> +            maxim,strings = <1 1 1 1>;
> +        };
> +    };
> +
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 7b7396ed28a700a2aab318553ce8ba1788312bff..5a592eefbe7562734aada05ab9e3aea8cee010e7 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -15069,6 +15069,11 @@ F:	Documentation/userspace-api/media/drivers/max2175.rst
>  F:	drivers/media/i2c/max2175*
>  F:	include/uapi/linux/max2175.h
>
> +MAX25014 BACKLIGHT DRIVER
> +M:	Maud Spierings <maudspierings@gocontroll.com>
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
> +
>  MAX31335 RTC DRIVER
>  M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
>  L:	linux-rtc@vger.kernel.org
>
> --
> 2.51.0
>
>

Re: [PATCH v3 1/4] dt-bindings: backlight: Add max25014 bindingsy

[Maud Spierings]

Hi Frank,
Thanks for the review.

On 9/11/25 17:33, Frank Li wrote:
> On Thu, Sep 11, 2025 at 09:53:18AM +0200, Maud Spierings via B4 Relay wrote:
>> From: Maud Spierings <maudspierings@gocontroll.com>
>>
>> The Maxim MAX25014 is a 4-channel automotive grade backlight driver IC
>> with integrated boost controller.
>>
>> Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
>> ---
>>   .../bindings/leds/backlight/maxim,max25014.yaml    | 81 ++++++++++++++++++++++
>>   MAINTAINERS                                        |  5 ++
>>   2 files changed, 86 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml b/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
>> new file mode 100644
>> index 0000000000000000000000000000000000000000..e113a2ad16aa74f982b9c2ea80578aed2d9424fe
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
>> @@ -0,0 +1,81 @@
>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/leds/backlight/maxim,max25014.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Maxim max25014 backlight controller
>> +
>> +maintainers:
>> +  - Maud Spierings <maudspierings@gocontroll.com>
>> +
>> +allOf:
>> +  - $ref: common.yaml#
>> +
>> +properties:
>> +  compatible:
>> +    enum:
>> +      - maxim,max25014
>> +
>> +  reg:
>> +    maxItems: 1
>> +
>> +  enable-gpios:
>> +    maxItems: 1
>> +
>> +  interrupts:
>> +    maxItems: 1
>> +
>> +  power-supply:
>> +    description: Regulator which controls the boost converter input rail.
>> +
>> +  pwms:
>> +    maxItems: 1
>> +
>> +  maxim,iset:
>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    maximum: 15
>> +    default: 11
>> +    description:
>> +      Value of the ISET register field. This controls the current scale of the
>> +      outputs, a higher number means more current.
> 
> Use standard unit. Do not use register value directly.

It is unfortunately not just a value in Amps, it depends on the hardware 
design. There is a kind of "default" table with a 49.9K resistor, but 
depending on that resistor the current is different.

>> +
>> +  maxim,strings:
>> +    $ref: /schemas/types.yaml#/definitions/uint32-array
>> +    description:
>> +      A 4-bit bitfield that describes which led strings to turn on.
>> +    minItems: 4
>> +    maxItems: 4
>> +    items:
>> +      maximum: 1
> 
> led should have standard interface.
> 
> check  Documentation/devicetree/bindings/leds/common.yaml

Thanks I will investigate, that may indeed be a better abstraction.

Kind regards,
Maud

Re: [PATCH v3 1/4] dt-bindings: backlight: Add max25014 bindingsy

[Frank Li]

On Fri, Sep 12, 2025 at 08:17:09AM +0200, Maud Spierings wrote:
> Hi Frank,
> Thanks for the review.
>
> On 9/11/25 17:33, Frank Li wrote:
> > On Thu, Sep 11, 2025 at 09:53:18AM +0200, Maud Spierings via B4 Relay wrote:
> > > From: Maud Spierings <maudspierings@gocontroll.com>
> > >
> > > The Maxim MAX25014 is a 4-channel automotive grade backlight driver IC
> > > with integrated boost controller.
> > >
> > > Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
> > > ---
> > >   .../bindings/leds/backlight/maxim,max25014.yaml    | 81 ++++++++++++++++++++++
> > >   MAINTAINERS                                        |  5 ++
> > >   2 files changed, 86 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml b/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
> > > new file mode 100644
> > > index 0000000000000000000000000000000000000000..e113a2ad16aa74f982b9c2ea80578aed2d9424fe
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
> > > @@ -0,0 +1,81 @@
> > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/leds/backlight/maxim,max25014.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Maxim max25014 backlight controller
> > > +
> > > +maintainers:
> > > +  - Maud Spierings <maudspierings@gocontroll.com>
> > > +
> > > +allOf:
> > > +  - $ref: common.yaml#
> > > +
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - maxim,max25014
> > > +
> > > +  reg:
> > > +    maxItems: 1
> > > +
> > > +  enable-gpios:
> > > +    maxItems: 1
> > > +
> > > +  interrupts:
> > > +    maxItems: 1
> > > +
> > > +  power-supply:
> > > +    description: Regulator which controls the boost converter input rail.
> > > +
> > > +  pwms:
> > > +    maxItems: 1
> > > +
> > > +  maxim,iset:
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    maximum: 15
> > > +    default: 11
> > > +    description:
> > > +      Value of the ISET register field. This controls the current scale of the
> > > +      outputs, a higher number means more current.
> >
> > Use standard unit. Do not use register value directly.
>
> It is unfortunately not just a value in Amps, it depends on the hardware
> design. There is a kind of "default" table with a 49.9K resistor, but
> depending on that resistor the current is different.

You should calculate in your driver. if 49.9K is dependence, you should
add xxx_ohm at dts.

Frank

>
> > > +
> > > +  maxim,strings:
> > > +    $ref: /schemas/types.yaml#/definitions/uint32-array
> > > +    description:
> > > +      A 4-bit bitfield that describes which led strings to turn on.
> > > +    minItems: 4
> > > +    maxItems: 4
> > > +    items:
> > > +      maximum: 1
> >
> > led should have standard interface.
> >
> > check  Documentation/devicetree/bindings/leds/common.yaml
>
> Thanks I will investigate, that may indeed be a better abstraction.
>
> Kind regards,
> Maud
>

Re: [PATCH v3 2/4] backlight: add max25014atg backlight

[Daniel Thompson]

On Thu, Sep 11, 2025 at 09:53:19AM +0200, Maud Spierings via B4 Relay wrote:
> diff --git a/drivers/video/backlight/max25014.c b/drivers/video/backlight/max25014.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..f4ca79dfc39ccb04702e6114c35a5863f80b8853
> --- /dev/null
> +++ b/drivers/video/backlight/max25014.c
> @@ -0,0 +1,394 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Backlight driver for Maxim MAX25014
> + *
> + * Copyright (C) 2025 GOcontroll B.V.
> + * Author: Maud Spierings <maudspierings@gocontroll.com>
> + */
> +
> +#include <linux/backlight.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/i2c.h>
> +#include <linux/regmap.h>
> +#include <linux/slab.h>
> +
> +#define MAX25014_ISET_DEFAULT_100 11
> +#define MAX_BRIGHTNESS            100
> +#define MIN_BRIGHTNESS            0
> +#define TON_MAX                   130720 /* @153Hz */
> +#define TON_STEP                  1307 /* @153Hz */
> +#define TON_MIN                   0
> +
> +#define MAX25014_DEV_ID           0x00
> +#define MAX25014_REV_ID           0x01
> +#define MAX25014_ISET             0x02
> +#define MAX25014_IMODE            0x03
> +#define MAX25014_TON1H            0x04
> +#define MAX25014_TON1L            0x05
> +#define MAX25014_TON2H            0x06
> +#define MAX25014_TON2L            0x07
> +#define MAX25014_TON3H            0x08
> +#define MAX25014_TON3L            0x09
> +#define MAX25014_TON4H            0x0A
> +#define MAX25014_TON4L            0x0B
> +#define MAX25014_TON_1_4_LSB      0x0C
> +#define MAX25014_SETTING          0x12
> +#define MAX25014_DISABLE          0x13
> +#define MAX25014_BSTMON           0x14
> +#define MAX25014_IOUT1            0x15
> +#define MAX25014_IOUT2            0x16
> +#define MAX25014_IOUT3            0x17
> +#define MAX25014_IOUT4            0x18
> +#define MAX25014_OPEN             0x1B
> +#define MAX25014_SHORT_GND        0x1C
> +#define MAX25014_SHORT_LED        0x1D
> +#define MAX25014_MASK             0x1E
> +#define MAX25014_DIAG             0x1F
> +
> +#define MAX25014_IMODE_HDIM       BIT(2)
> +#define MAX25014_ISET_ENABLE      BIT(5)
> +#define MAX25014_ISET_PSEN        BIT(4)
> +#define MAX25014_DIAG_HW_RST      BIT(2)
> +#define MAX25014_SETTING_FPWM     GENMASK(6, 4)
> +
> +struct max25014 {
> +	struct i2c_client *client;
> +	struct backlight_device *bl;
> +	struct regmap *regmap;
> +	struct gpio_desc *enable;
> +	struct regulator *vin; /* regulator for boost converter Vin rail */
> +	uint32_t iset;
> +	uint8_t strings_mask;
> +};
> +
> +static const struct regmap_config max25014_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +	.max_register = MAX25014_DIAG,
> +};
> +
> +/**
> + * @brief control the brightness with i2c registers
> + *
> + * @param regmap trivial
> + * @param brt brightness
> + * @return int
> + */
> +static int max25014_register_control(struct regmap *regmap, uint32_t brt)
> +{
> +	uint32_t reg = TON_STEP * brt;
> +	int ret;
> +	/*
> +	 * 18 bit number lowest, 2 bits in first register,
> +	 * next lowest 8 in the L register, next 8 in the H register
> +	 * Seemingly setting the strength of only one string controls all of
> +	 * them, individual settings don't affect the outcome.
> +	 */
> +
> +	ret = regmap_write(regmap, MAX25014_TON_1_4_LSB, reg & 0b00000011);
> +	if (ret != 0)
> +		return ret;
> +	ret = regmap_write(regmap, MAX25014_TON1L, (reg >> 2) & 0b11111111);
> +	if (ret != 0)
> +		return ret;
> +	return regmap_write(regmap, MAX25014_TON1H, (reg >> 10) & 0b11111111);
> +}
> +
> +static int max25014_check_errors(struct max25014 *maxim)
> +{
> +	uint8_t i;
> +	int ret;
> +	uint32_t val;
> +
> +	ret = regmap_read(maxim->regmap, MAX25014_OPEN, &val);
> +	if (ret != 0)
> +		return ret;
> +	if (val > 0) {
> +		dev_err(&maxim->client->dev, "Open led strings detected on:\n");
> +		for (i = 0; i < 4; i++) {
> +			if (val & 1 << i)
> +				dev_err(&maxim->client->dev, "string %d\n", i + 1);
> +		}
> +		return -EIO;
> +	}
> +
> +	ret = regmap_read(maxim->regmap, MAX25014_SHORT_GND, &val);
> +	if (ret != 0)
> +		return ret;
> +	if (val > 0) {
> +		dev_err(&maxim->client->dev, "Short to ground detected on:\n");
> +		for (i = 0; i < 4; i++) {
> +			if (val & 1 << i)
> +				dev_err(&maxim->client->dev, "string %d\n", i + 1);
> +		}
> +		return -EIO;
> +	}
> +
> +	ret = regmap_read(maxim->regmap, MAX25014_SHORT_GND, &val);
> +	if (ret != 0)
> +		return ret;
> +	if (val > 0) {
> +		dev_err(&maxim->client->dev, "Shorted led detected on:\n");
> +		for (i = 0; i < 4; i++) {
> +			if (val & 1 << i)
> +				dev_err(&maxim->client->dev, "string %d\n", i + 1);
> +		}
> +		return -EIO;
> +	}
> +
> +	ret = regmap_read(maxim->regmap, MAX25014_DIAG, &val);
> +	if (ret != 0)
> +		return ret;
> +	/*
> +	 * The HW_RST bit always starts at 1 after power up.
> +	 * It is reset on first read, does not indicate an error.
> +	 */
> +	if (val > 0 && val != MAX25014_DIAG_HW_RST) {
> +		if (val & 0b1)
> +			dev_err(&maxim->client->dev, "Overtemperature shutdown\n");
> +		if (val & 0b10)
> +			dev_warn(&maxim->client->dev,
> +				 "Chip is getting too hot (>125C)\n");

The dev_warn() looks a bit odd here. Even through the hardware is alive
the drive reacts to this warning by refusing to probe.

That problem means this should be dev_err() like all the other issues
here.


> +		if (val & 0b1000)
> +			dev_err(&maxim->client->dev, "Boost converter overvoltage\n");
> +		if (val & 0b10000)
> +			dev_err(&maxim->client->dev, "Boost converter undervoltage\n");
> +		if (val & 0b100000)
> +			dev_err(&maxim->client->dev, "IREF out of range\n");
> +		return -EIO;
> +	}
> +	return 0;
> +}
> +
> +/*
> + * 1. disable unused strings
> + * 2. set dim mode
> + * 3. set initial brightness
> + * 4. set setting register
> + * 5. enable the backlight
> + */
> +static int max25014_configure(struct max25014 *maxim, uint32_t initial_brightness)
> +{
> +	int ret;
> +	uint32_t val;
> +
> +	ret = regmap_write(maxim->regmap, MAX25014_DISABLE,
> +			   maxim->strings_mask);
> +	if (ret != 0)
> +		return ret;
> +
> +	ret = regmap_write(maxim->regmap, MAX25014_IMODE, MAX25014_IMODE_HDIM);
> +	if (ret != 0)
> +		return ret;
> +
> +	max25014_register_control(maxim->regmap,
> +				  initial_brightness);
> +
> +	ret = regmap_read(maxim->regmap, MAX25014_SETTING, &val);
> +	if (ret != 0)
> +		return ret;
> +
> +	ret = regmap_write(
> +		maxim->regmap, MAX25014_SETTING,
> +		val & ~MAX25014_SETTING_FPWM);
> +	if (ret != 0)
> +		return ret;
> +
> +	ret = regmap_write(maxim->regmap, MAX25014_ISET,
> +			   maxim->iset | MAX25014_ISET_ENABLE | MAX25014_ISET_PSEN);
> +	return ret;
> +}
> +
> +static int max25014_update_status(struct backlight_device *bl_dev)
> +{
> +	struct max25014 *maxim = bl_get_data(bl_dev);
> +
> +	if (bl_dev->props.state & BL_CORE_SUSPENDED)
> +		bl_dev->props.brightness = 0;

This should be using the backlight_is_blank() helper rather than
fiddling with the state variables.


> +
> +	return max25014_register_control(maxim->regmap, bl_dev->props.brightness);
> +}
> +
> +static const struct backlight_ops max25014_bl_ops = {
> +	.options = BL_CORE_SUSPENDRESUME,
> +	.update_status = max25014_update_status,
> +};
> +
> +static int max25014_parse_dt(struct max25014 *maxim, uint32_t *initial_brightness)
> +{
> +	struct device *dev = &maxim->client->dev;
> +	struct device_node *node = dev->of_node;
> +	uint32_t strings[4];
> +	int res, i;
> +
> +	if (!node) {
> +		dev_err(dev, "no platform data\n");
> +		return -EINVAL;
> +	}
> +
> +	res = of_property_count_u32_elems(node, "maxim,strings");
> +	if (res == 4) {
> +		of_property_read_u32_array(node, "maxim,strings", strings, 4);
> +	} else {
> +		dev_err(dev, "strings property not correctly defined\n");
> +		return -EINVAL;
> +	}
> +
> +	for (i = 0; i < 4; i++) {
> +		if (strings[i] == 0)
> +			maxim->strings_mask |= 1 << i;
> +	}
> +
> +	*initial_brightness = 50U;
> +	of_property_read_u32(node, "default-brightness", initial_brightness);
> +	maxim->iset = MAX25014_ISET_DEFAULT_100;
> +	of_property_read_u32(node, "maxim,iset", &maxim->iset);
> +
> +	if (maxim->iset < 0 || maxim->iset > 15) {
> +		dev_err(dev,
> +			"Invalid iset, should be a value from 0-15, entered was %d\n",
> +			maxim->iset);
> +		return -EINVAL;
> +	}
> +
> +	if (*initial_brightness < 0 || *initial_brightness > 100) {
> +		dev_err(dev,
> +			"Invalid initial brightness, should be a value from 0-100, entered was %d\n",
> +			*initial_brightness);
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +static int max25014_probe(struct i2c_client *cl)
> +{
> +	struct backlight_device *bl;
> +	const struct i2c_device_id *id = i2c_client_get_device_id(cl);
> +	struct max25014 *maxim;
> +	struct backlight_properties props;
> +	int ret;
> +	uint32_t initial_brightness;
> +
> +	maxim = devm_kzalloc(&cl->dev, sizeof(struct max25014), GFP_KERNEL);
> +	if (!maxim)
> +		return -ENOMEM;
> +
> +	maxim->client = cl;
> +
> +	ret = max25014_parse_dt(maxim, &initial_brightness);
> +	if (ret < 0)
> +		return ret;
> +
> +	maxim->vin = devm_regulator_get(&maxim->client->dev, "power");
> +	if (IS_ERR(maxim->vin)) {
> +		if (PTR_ERR(maxim->vin) == -EPROBE_DEFER)
> +			return -EPROBE_DEFER;
> +		maxim->vin = NULL;
> +	}
> +
> +	if (maxim->vin) {
> +		ret = regulator_enable(maxim->vin);
> +		if (ret < 0) {
> +			dev_err(&maxim->client->dev, "failed to enable Vin: %d\n", ret);
> +			return ret;
> +		}
> +	}
> +
> +	maxim->enable =
> +		devm_gpiod_get_optional(&maxim->client->dev, "enable", GPIOD_ASIS);
> +	if (IS_ERR(maxim->enable)) {
> +		ret = PTR_ERR(maxim->enable);
> +		dev_err(&maxim->client->dev, "failed to get enable gpio: %d\n", ret);
> +		goto disable_vin;
> +	}
> +
> +	if (maxim->enable) {
> +		gpiod_set_value_cansleep(maxim->enable, 1);
> +
> +		/* Datasheet Electrical Characteristics tSTARTUP 2ms */
> +		usleep_range(2000, 2500);
> +	}
> +
> +	maxim->regmap = devm_regmap_init_i2c(cl, &max25014_regmap_config);
> +	if (IS_ERR(maxim->regmap)) {
> +		ret = PTR_ERR(maxim->regmap);
> +		dev_err(&maxim->client->dev, "failed to initialize the i2c regmap: %d\n", ret);
> +		goto disable_full;
> +	}
> +
> +	i2c_set_clientdata(cl, maxim);
> +
> +	ret = max25014_check_errors(maxim);
> +	if (ret) { /* error is already reported in the above function */
> +		goto disable_full;
> +	}
> +
> +	ret = max25014_configure(maxim, initial_brightness);
> +	if (ret) {
> +		dev_err(&maxim->client->dev, "device config err: %d", ret);
> +		goto disable_full;
> +	}
> +
> +	memset(&props, 0, sizeof(props));
> +	props.type = BACKLIGHT_PLATFORM;
> +	props.max_brightness = MAX_BRIGHTNESS;

Please ensure that props.scale is set to something better than UNKNOWN.


Daniel.

Re: [PATCH v3 1/4] dt-bindings: backlight: Add max25014 bindingsy

[Maud Spierings]

On 9/12/25 17:22, Frank Li wrote:
> On Fri, Sep 12, 2025 at 08:17:09AM +0200, Maud Spierings wrote:
>> Hi Frank,
>> Thanks for the review.
>>
>> On 9/11/25 17:33, Frank Li wrote:
>>> On Thu, Sep 11, 2025 at 09:53:18AM +0200, Maud Spierings via B4 Relay wrote:
>>>> From: Maud Spierings <maudspierings@gocontroll.com>
>>>>
>>>> The Maxim MAX25014 is a 4-channel automotive grade backlight driver IC
>>>> with integrated boost controller.
>>>>
>>>> Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
>>>> ---
>>>>    .../bindings/leds/backlight/maxim,max25014.yaml    | 81 ++++++++++++++++++++++
>>>>    MAINTAINERS                                        |  5 ++
>>>>    2 files changed, 86 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml b/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
>>>> new file mode 100644
>>>> index 0000000000000000000000000000000000000000..e113a2ad16aa74f982b9c2ea80578aed2d9424fe
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
>>>> @@ -0,0 +1,81 @@
>>>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: http://devicetree.org/schemas/leds/backlight/maxim,max25014.yaml#
>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>> +
>>>> +title: Maxim max25014 backlight controller
>>>> +
>>>> +maintainers:
>>>> +  - Maud Spierings <maudspierings@gocontroll.com>
>>>> +
>>>> +allOf:
>>>> +  - $ref: common.yaml#
>>>> +
>>>> +properties:
>>>> +  compatible:
>>>> +    enum:
>>>> +      - maxim,max25014
>>>> +
>>>> +  reg:
>>>> +    maxItems: 1
>>>> +
>>>> +  enable-gpios:
>>>> +    maxItems: 1
>>>> +
>>>> +  interrupts:
>>>> +    maxItems: 1
>>>> +
>>>> +  power-supply:
>>>> +    description: Regulator which controls the boost converter input rail.
>>>> +
>>>> +  pwms:
>>>> +    maxItems: 1
>>>> +
>>>> +  maxim,iset:
>>>> +    $ref: /schemas/types.yaml#/definitions/uint32
>>>> +    maximum: 15
>>>> +    default: 11
>>>> +    description:
>>>> +      Value of the ISET register field. This controls the current scale of the
>>>> +      outputs, a higher number means more current.
>>>
>>> Use standard unit. Do not use register value directly.
>>
>> It is unfortunately not just a value in Amps, it depends on the hardware
>> design. There is a kind of "default" table with a 49.9K resistor, but
>> depending on that resistor the current is different.
> 
> You should calculate in your driver. if 49.9K is dependence, you should
> add xxx_ohm at dts.

I've tried to find the logic behind the Riref resistor and its 
values/effects, but there is no formula for it, there are example values 
for 49.9k and 40.2k, besides that all that is stated that the minimum 
allowed value is 27.5k and the maximum value is 83.5k.

Not sure how to continue after that, I cannot verify/approximate any 
relation with only two data points.
Kind regards,
Maud