[PATCH v8 0/4] backlight: add new max25014 backlight driver

[PATCH v8 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 v8:
- Clean up some leftovers from the led subnodes, address/size-cells (Rob)
- Add Robs rb tag
- Add Daniels rb tag
- Bring the Kconfig option in line text wise with other drivers
- Rebase on the latest next
- Link to v7: https://lore.kernel.org/r/20260123-max25014-v7-0-15e504b9acc7@gocontroll.com

Changes in v7:
- remove the led subnodes
- always enable the regulator by using devm_regulator_get_enable()
- remove the no longer required gotos and simplify early returns
- fix the name of the SHORTED_LED error field
- fix the name of the SHORTGND error field
- use the proper backlight helper functions for setting/getting
  brightness
- Link to v6: https://lore.kernel.org/r/20251201-max25014-v6-0-88e3ac8112ff@gocontroll.com

Changes in v6:
- fixup changes in v4 where default brightness handling was changed but
  not noted
- remove leftover comment about initializing brightness
- use BIT definitions for fields in the DIAG register
- apply reverse christmas tree initialization of local variables
- remove !=0 from checks, just check if (ret)
- remove > 0 from checks, just check if (val)
- use dev_err_probe() more
- set enable gpio high in the get() instead of seperately calling set()
- change usleep_range() to fsleep()
- remove null checks when setting gpio value
- get regular regulator, not optional to avoid further NULL checks in
  case none is provided
- introduce max25014_initial_power_state() to check if the bootloader
  has already initialized the backlight and to correctly set props.power
- squash max25014_register_control() into max25014_update_status()
- in max25014_configure() perform extra checking on the DISABLE register
  now that the state from the bootloader is taken into account
- Link to v5: https://lore.kernel.org/r/20251107-max25014-v5-0-9a6aa57306bf@gocontroll.com

Changes in v5:
- moved comment about current functions of the driver to the actual
  comment section of the commit
- fixed the led@0 property, regex patternProperty is not needed as of
  now
- added extra clarification about the ISET field/register
- moved #address-cells and #size-cells to the correct location
- remove leftover default-brightness in backlight nodes
- Link to v4: https://lore.kernel.org/r/20251009-max25014-v4-0-6adb2a0aa35f@gocontroll.com

Changes in v4:
- remove setting default brightness, let backlight core take care of it
- use a led node to describe the backlight
- use led-sources to enable specific channels
- also wait 2ms when there is a supply but no enable
- change dev_warn() to dev_err() in error path in max25014_check_errors()
- set backlight_properties.scale to BACKLIGHT_SCALE_LINEAR
- rebase latest next
- add address-cells and size-cells to i2c4 in av101hdt-a10.dtso
- Link to v3: https://lore.kernel.org/r/20250911-max25014-v3-0-d03f4eba375e@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 support
      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    |  83 +++++
 MAINTAINERS                                        |   6 +
 ...x8p-ml81-moduline-display-106-av101hdt-a10.dtso |  24 ++
 ...x8p-ml81-moduline-display-106-av123z7m-n17.dtso |  19 +-
 drivers/video/backlight/Kconfig                    |   7 +
 drivers/video/backlight/Makefile                   |   1 +
 drivers/video/backlight/max25014.c                 | 377 +++++++++++++++++++++
 7 files changed, 516 insertions(+), 1 deletion(-)
---
base-commit: f3e6330d7fe42b204af05a2dbc68b379e0ad179e
change-id: 20250626-max25014-4207591e1af5

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

[PATCH v8 1/4] dt-bindings: backlight: Add max25014 support

[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.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
---

In the current implementation the control registers for channel 1,
control all channels. So only one led subnode with led-sources is
supported right now. If at some point the driver functionality is
expanded the bindings can be easily extended with it.
---
 .../bindings/leds/backlight/maxim,max25014.yaml    | 83 ++++++++++++++++++++++
 MAINTAINERS                                        |  5 ++
 2 files changed, 88 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 0000000000000..d00be2e081938
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/backlight/maxim,max25014.yaml
@@ -0,0 +1,83 @@
+# 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>
+
+properties:
+  compatible:
+    enum:
+      - maxim,max25014
+
+  reg:
+    maxItems: 1
+
+  default-brightness:
+    minimum: 0
+    maximum: 100
+    default: 50
+
+  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 field in the ISET register. 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
+    default:
+      [1 1 1 1]
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: 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 0>;
+        };
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index 10d12b51b1f6f..7e3ad236537fe 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15688,6 +15688,11 @@ 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

-- 
2.53.0

[PATCH v8 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.

Reviewed-by: Daniel Thompson (RISCstar) <danielt@kernel.org>
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 | 377 +++++++++++++++++++++++++++++++++++++
 4 files changed, 386 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 7e3ad236537fe..1f1a5326a6aab 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15692,6 +15692,7 @@ 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 a7a3fbaf7c29e..f4e99542ffe8f 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -282,6 +282,13 @@ config BACKLIGHT_DA9052
 	help
 	  Enable the Backlight Driver for DA9052-BC and DA9053-AA/Bx PMICs.
 
+config BACKLIGHT_MAX25014
+	tristate "Backlight driver for Maxim MAX25014"
+	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 794820a98ed49..21c8313cfb121 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -47,6 +47,7 @@ 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 0000000000000..3ee45617261f3
--- /dev/null
+++ b/drivers/video/backlight/max25014.c
@@ -0,0 +1,377 @@
+// 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_SHORTGND         0x1C
+#define MAX25014_SHORTED_LED      0x1D
+#define MAX25014_MASK             0x1E
+#define MAX25014_DIAG             0x1F
+
+#define MAX25014_ISET_ENA         BIT(5)
+#define MAX25014_ISET_PSEN        BIT(4)
+#define MAX25014_IMODE_HDIM       BIT(2)
+#define MAX25014_SETTING_FPWM     GENMASK(6, 4)
+#define MAX25014_DISABLE_DIS_MASK GENMASK(3, 0)
+#define MAX25014_DIAG_OT          BIT(0)
+#define MAX25014_DIAG_OTW         BIT(1)
+#define MAX25014_DIAG_HW_RST      BIT(2)
+#define MAX25014_DIAG_BSTOV       BIT(3)
+#define MAX25014_DIAG_BSTUV       BIT(4)
+#define MAX25014_DIAG_IREFOOR     BIT(5)
+
+struct max25014 {
+	struct i2c_client *client;
+	struct backlight_device *bl;
+	struct regmap *regmap;
+	struct gpio_desc *enable;
+	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,
+};
+
+static int max25014_initial_power_state(struct max25014 *maxim)
+{
+	uint32_t val;
+	int ret;
+
+	ret = regmap_read(maxim->regmap, MAX25014_ISET, &val);
+	if (ret)
+		return ret;
+
+	return val & MAX25014_ISET_ENA ? BACKLIGHT_POWER_ON : BACKLIGHT_POWER_OFF;
+}
+
+static int max25014_check_errors(struct max25014 *maxim)
+{
+	uint32_t val;
+	uint8_t i;
+	int ret;
+
+	ret = regmap_read(maxim->regmap, MAX25014_OPEN, &val);
+	if (ret)
+		return ret;
+	if (val) {
+		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_SHORTGND, &val);
+	if (ret)
+		return ret;
+	if (val) {
+		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_SHORTED_LED, &val);
+	if (ret)
+		return ret;
+	if (val) {
+		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)
+		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 && val != MAX25014_DIAG_HW_RST) {
+		if (val & MAX25014_DIAG_OT)
+			dev_err(&maxim->client->dev,
+				"Overtemperature shutdown\n");
+		if (val & MAX25014_DIAG_OTW)
+			dev_err(&maxim->client->dev,
+				 "Chip is getting too hot (>125C)\n");
+		if (val & MAX25014_DIAG_BSTOV)
+			dev_err(&maxim->client->dev,
+				"Boost converter overvoltage\n");
+		if (val & MAX25014_DIAG_BSTUV)
+			dev_err(&maxim->client->dev,
+				"Boost converter undervoltage\n");
+		if (val & MAX25014_DIAG_IREFOOR)
+			dev_err(&maxim->client->dev, "IREF out of range\n");
+		return -EIO;
+	}
+	return 0;
+}
+
+/*
+ * 1. disable unused strings
+ * 2. set dim mode
+ * 3. set setting register
+ * 4. enable the backlight
+ */
+static int max25014_configure(struct max25014 *maxim, int initial_state)
+{
+	uint32_t val;
+	int ret;
+
+	ret = regmap_read(maxim->regmap, MAX25014_DISABLE, &val);
+	if (ret)
+		return ret;
+
+	/*
+	 * Strings can only be disabled when MAX25014_ISET_ENA == 0, check if
+	 * it needs to be changed at all to prevent the backlight flashing when
+	 * it is configured correctly by the bootloader
+	 */
+	if (!((val & MAX25014_DISABLE_DIS_MASK) == maxim->strings_mask)) {
+		if (initial_state == BACKLIGHT_POWER_ON) {
+			ret = regmap_write(maxim->regmap, MAX25014_ISET, 0);
+			if (ret)
+				return ret;
+		}
+		ret = regmap_write(maxim->regmap, MAX25014_DISABLE, maxim->strings_mask);
+		if (ret)
+			return ret;
+	}
+
+	ret = regmap_write(maxim->regmap, MAX25014_IMODE, MAX25014_IMODE_HDIM);
+	if (ret)
+		return ret;
+
+	ret = regmap_read(maxim->regmap, MAX25014_SETTING, &val);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(maxim->regmap, MAX25014_SETTING,
+			   val & ~MAX25014_SETTING_FPWM);
+	if (ret)
+		return ret;
+
+	return regmap_write(maxim->regmap, MAX25014_ISET,
+			   maxim->iset | MAX25014_ISET_ENA |
+			   MAX25014_ISET_PSEN);
+}
+
+static int max25014_update_status(struct backlight_device *bl_dev)
+{
+	struct max25014 *maxim = bl_get_data(bl_dev);
+	uint32_t reg;
+	int ret;
+
+	reg  = TON_STEP * backlight_get_brightness(bl_dev);
+
+	/*
+	 * 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(maxim->regmap, MAX25014_TON_1_4_LSB, reg & 0b00000011);
+	if (ret != 0)
+		return ret;
+	ret = regmap_write(maxim->regmap, MAX25014_TON1L, (reg >> 2) & 0b11111111);
+	if (ret != 0)
+		return ret;
+	return regmap_write(maxim->regmap, MAX25014_TON1H, (reg >> 10) & 0b11111111);
+}
+
+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;
+
+	res = of_property_count_u32_elems(node, "maxim,strings");
+	if (res == 4) {
+		of_property_read_u32_array(node, "maxim,strings", strings, 4);
+		for (i = 0; i < 4; i++) {
+			if (strings[i] == 0)
+				maxim->strings_mask |= 1 << i;
+	}
+	} else {
+		maxim->strings_mask = 0;
+	}
+
+	*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 > 15)
+		return dev_err_probe(dev, -EINVAL,
+				     "Invalid iset, should be a value from 0-15, entered was %d\n",
+				     maxim->iset);
+
+	if (*initial_brightness > 100)
+		return dev_err_probe(dev, -EINVAL,
+				     "Invalid initial brightness, should be a value from 0-100, entered was %d\n",
+				     *initial_brightness);
+
+	return 0;
+}
+
+static int max25014_probe(struct i2c_client *cl)
+{
+	const struct i2c_device_id *id = i2c_client_get_device_id(cl);
+	struct backlight_properties props;
+	uint32_t initial_brightness = 50;
+	struct backlight_device *bl;
+	struct max25014 *maxim;
+	int ret;
+
+	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)
+		return ret;
+
+	ret = devm_regulator_get_enable(&maxim->client->dev, "power");
+	if (ret)
+		return dev_err_probe(&maxim->client->dev, ret,
+				     "failed to get power-supply");
+
+	maxim->enable = devm_gpiod_get_optional(&maxim->client->dev, "enable",
+						GPIOD_OUT_HIGH);
+	if (IS_ERR(maxim->enable))
+		return dev_err_probe(&maxim->client->dev, PTR_ERR(maxim->enable),
+				    "failed to get enable gpio\n");
+
+	/* Datasheet Electrical Characteristics tSTARTUP 2ms */
+	fsleep(2000);
+
+	maxim->regmap = devm_regmap_init_i2c(cl, &max25014_regmap_config);
+	if (IS_ERR(maxim->regmap))
+		return dev_err_probe(&maxim->client->dev, PTR_ERR(maxim->regmap),
+			"failed to initialize the i2c regmap\n");
+
+	i2c_set_clientdata(cl, maxim);
+
+	ret = max25014_check_errors(maxim);
+	if (ret) /* error is already reported in the above function */
+		return ret;
+
+	ret = max25014_initial_power_state(maxim);
+	if (ret < 0)
+		return dev_err_probe(&maxim->client->dev, ret, "Could not get enabled state\n");
+
+	memset(&props, 0, sizeof(struct backlight_properties));
+	props.type = BACKLIGHT_PLATFORM;
+	props.max_brightness = MAX_BRIGHTNESS;
+	props.brightness = initial_brightness;
+	props.scale = BACKLIGHT_SCALE_LINEAR;
+	props.power = ret;
+
+	ret = max25014_configure(maxim, ret);
+	if (ret)
+		return dev_err_probe(&maxim->client->dev, ret, "device config error");
+
+	bl = devm_backlight_device_register(&maxim->client->dev, id->name,
+					    &maxim->client->dev, maxim,
+					    &max25014_bl_ops, &props);
+	if (IS_ERR(bl))
+		return dev_err_probe(&maxim->client->dev, PTR_ERR(bl),
+				    "failed to register backlight\n");
+
+	maxim->bl = bl;
+
+	backlight_update_status(maxim->bl);
+
+	return 0;
+}
+
+static void max25014_remove(struct i2c_client *cl)
+{
+	struct max25014 *maxim = i2c_get_clientdata(cl);
+
+	backlight_device_set_brightness(maxim->bl, 0);
+	gpiod_set_value_cansleep(maxim->enable, 0);
+}
+
+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");

-- 
2.53.0

[PATCH v8 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>
---
 ...x8p-ml81-moduline-display-106-av101hdt-a10.dtso | 24 ++++++++++++++++++++++
 1 file changed, 24 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 c6fc5d5b1e5fa..23e4bf64b28b5 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 +41,30 @@ reg_vbus: regulator-vbus {
 	};
 };
 
+&i2c4 {
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	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

-- 
2.53.0

[PATCH v8 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 3eb665ce9d5d2..0b969c8c04db1 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

-- 
2.53.0

Claude review: backlight: add new max25014 backlight driver

[Claude Code Review Bot]

Overall Series Review

Subject: backlight: add new max25014 backlight driver
Author: Maud Spierings via B4 Relay
 <devnull+maudspierings.gocontroll.com@kernel.org>
Patches: 5
Reviewed: 2026-04-12T13:25:20.719247

---

This is a well-structured 4-patch series adding a new driver for the Maxim MAX25014 automotive backlight controller. The series is at v8 and has already received Reviewed-by tags from Rob Herring (binding) and Daniel Thompson (driver). The overall shape is good: binding first, then driver, then DTS consumers. However, there are several issues ranging from minor style nits to a few substantive problems that should be addressed.

**Key concerns:**
1. Missing `#include <linux/regulator/consumer.h>` in the driver
2. `of_match_ptr()` usage is discouraged for new drivers
3. Indentation bug in `max25014_parse_dt`
4. The `remove` function doesn't fully shut down the hardware
5. Kernel type conventions (`u32`/`u8` preferred over `uint32_t`/`uint8_t`)
6. Binary literals are unusual in kernel code

---

---
Generated by Claude Code Patch Reviewer

Claude review: dt-bindings: backlight: Add max25014 support

[Claude Code Review Bot]

Patch Review

This patch adds the YAML binding and MAINTAINERS entry. It has Rob Herring's Reviewed-by.

**Minor observations:**

1. The `maxim,strings` description says "A 4-bit bitfield" but the representation is a 4-element array of `uint32`, not a bitfield. The description is slightly misleading — it's an array of 4 enable/disable flags, not a bitfield. Consider: "An array of 4 values (0 or 1) describing which LED strings to enable."

2. The binding declares `interrupts` and `pwms` properties but the driver doesn't implement either of these features. This is acceptable for forward-compatibility as documented in the cover letter, but it's worth noting.

3. The `default-brightness` property lacks a `$ref` to a type schema. While it will likely be inferred, adding `$ref: /schemas/types.yaml#/definitions/uint32` would be consistent with `maxim,iset`.

**No blocking issues.** The binding is clean and the Rob R-b carries weight.

---

---
Generated by Claude Code Patch Reviewer

Claude review: backlight: add max25014atg backlight

[Claude Code Review Bot]

Patch Review

This is the main driver patch. Several issues:

**Missing include (bug):**

The driver calls `devm_regulator_get_enable()` (line 290) but does not include `<linux/regulator/consumer.h>`. This works today only because the header is pulled in transitively through other headers, but that is fragile and will break if those transitive includes change. Add:
```c
#include <linux/regulator/consumer.h>
```

**`of_match_ptr()` usage (style/correctness):**

```c
.of_match_table = of_match_ptr(max25014_dt_ids),
```

Using `of_match_ptr()` is discouraged in new drivers. When `CONFIG_OF` is disabled, it evaluates to `NULL` and the `max25014_dt_ids` table becomes unused, generating a compiler warning. Just use the table directly:
```c
.of_match_table = max25014_dt_ids,
```

**Indentation bug in `max25014_parse_dt`:**

```c
for (i = 0; i < 4; i++) {
    if (strings[i] == 0)
        maxim->strings_mask |= 1 << i;
}
```

The closing `}` of the `for` loop appears to be indented at the level of the outer `if`, not at the `for` level. This is a whitespace-only issue but indicates sloppy formatting. (Visible at line 247 of the driver.)

**Kernel type conventions:**

The driver uses `uint32_t` and `uint8_t` throughout. Kernel convention strongly prefers `u32` and `u8`. Examples:

```c
uint32_t val;    /* should be: unsigned int val; (for regmap) or u32 */
uint8_t i;       /* should be: int i; or u8 */
uint32_t iset;   /* should be: u32 iset; */
uint8_t strings_mask; /* should be: u8 strings_mask; */
```

Note: `regmap_read()` takes `unsigned int *`, so `val` should ideally be `unsigned int` rather than `uint32_t`/`u32` to match the API precisely.

**Binary literals:**

```c
ret = regmap_write(maxim->regmap, MAX25014_TON_1_4_LSB, reg & 0b00000011);
...
ret = regmap_write(maxim->regmap, MAX25014_TON1L, (reg >> 2) & 0b11111111);
...
return regmap_write(maxim->regmap, MAX25014_TON1H, (reg >> 10) & 0b11111111);
```

Binary literals (`0b...`) are a GCC extension. Kernel code conventionally uses hex: `0x03` and `0xFF`. Also, `& 0xFF` after writing to an 8-bit register via regmap is somewhat redundant since regmap will truncate to `val_bits`, but documenting the field widths explicitly is fine.

**Unnecessary double negation:**

```c
if (!((val & MAX25014_DISABLE_DIS_MASK) == maxim->strings_mask)) {
```

This is more clearly written as:
```c
if ((val & MAX25014_DISABLE_DIS_MASK) != maxim->strings_mask) {
```

**`remove` function doesn't fully disable the hardware:**

```c
static void max25014_remove(struct i2c_client *cl)
{
    struct max25014 *maxim = i2c_get_clientdata(cl);
    backlight_device_set_brightness(maxim->bl, 0);
    gpiod_set_value_cansleep(maxim->enable, 0);
}
```

Setting brightness to 0 only writes the TON registers. The ISET_ENA bit is left set, so the boost converter continues running after the driver is removed. You should also clear the ENA bit (e.g., write 0 to `MAX25014_ISET`) before pulling the enable GPIO low.

**Unchecked return value in `max25014_parse_dt`:**

```c
of_property_read_u32_array(node, "maxim,strings", strings, 4);
```

The return value of `of_property_read_u32_array()` is not checked. If the property exists but has the wrong format, this could silently leave `strings[]` uninitialized. Since you already checked `of_property_count_u32_elems` returned 4, this is low risk, but checking the return value would be more robust.

**Unused defines:**

`MIN_BRIGHTNESS` and `TON_MIN` are defined but never used. Remove them.

**Unnecessary `#include <linux/slab.h>`:**

`devm_kzalloc` is declared via `<linux/device.h>` which is pulled in transitively. The `slab.h` include is not strictly needed, though it's common practice and harmless.

**`ret` reuse pattern in probe:**

```c
ret = max25014_initial_power_state(maxim);
if (ret < 0)
    return dev_err_probe(...);
props.power = ret;
ret = max25014_configure(maxim, ret);
```

This works because `BACKLIGHT_POWER_ON` is 0 and `BACKLIGHT_POWER_OFF` is 4, so both are non-negative. But the dual use of `ret` as both error indicator and power state value is fragile and hard to read. Consider using a separate variable like `initial_state` for clarity.

**Operator precedence in `max25014_check_errors`:**

```c
if (val & 1 << i)
```

This relies on `<<` having higher precedence than `&`, which is correct in C, but adding parentheses `(val & (1 << i))` or using `BIT(i)` would improve readability and match the BIT() style used elsewhere in the file.

---

---
Generated by Claude Code Patch Reviewer

Claude review: arm64: dts: freescale: moduline-display-av101hdt-a10: add backlight

[Claude Code Review Bot]

Patch Review

This patch adds the backlight node to the av101hdt-a10 display overlay.

**Observation:**

```dts
&i2c4 {
    #address-cells = <1>;
    #size-cells = <0>;
```

Re-specifying `#address-cells` and `#size-cells` in an overlay that extends `&i2c4` is typically unnecessary since these are already defined in the base I2C controller node. It's harmless, but redundant.

**No other issues.** The pinctrl, enable GPIO, and device properties look correct and consistent with the binding.

---

---
Generated by Claude Code Patch Reviewer

Claude review: arm64: dts: freescale: moduline-display-av123z7m-n17: add backlight

[Claude Code Review Bot]

Patch Review

This patch replaces a placeholder comment `/* max25014 @ 0x6f */` with the actual device node.

```dts
-	/* max25014 @ 0x6f */
+	backlight: backlight@6f {
```

Clean replacement of the placeholder. The node properties are consistent with patch 3 except `maxim,strings = <1 1 1 1>` (all 4 strings enabled vs. 3 in patch 3), which makes sense for a different display panel.

**No issues with this patch.**

---

### Summary of required/recommended changes

| Priority | Issue | Patch |
|----------|-------|-------|
| Should fix | Missing `#include <linux/regulator/consumer.h>` | 2/4 |
| Should fix | Replace `of_match_ptr()` with direct reference | 2/4 |
| Should fix | Fix indentation of for-loop closing brace in `max25014_parse_dt` | 2/4 |
| Should fix | Disable hardware (clear ISET_ENA) in `max25014_remove` | 2/4 |
| Nit | Use `u32`/`u8` instead of `uint32_t`/`uint8_t` | 2/4 |
| Nit | Replace binary literals with hex | 2/4 |
| Nit | Simplify `!((x) == y)` to `(x) != y` | 2/4 |
| Nit | Use `BIT(i)` instead of `1 << i` in check_errors | 2/4 |
| Nit | Remove unused `MIN_BRIGHTNESS` and `TON_MIN` defines | 2/4 |
| Nit | Use a separate variable for initial power state in probe | 2/4 |

---
Generated by Claude Code Patch Reviewer