Message-Id: <20251201-max25014-v6-2-88e3ac8112ff@gocontroll.com>
Date: Mon, 01 Dec 2025 12:53:21 +0100
From: Maud Spierings via B4 Relay <devnull+maudspierings.gocontroll.com@...nel.org>
To: Lee Jones <lee@...nel.org>, Daniel Thompson <danielt@...nel.org>, 
 Jingoo Han <jingoohan1@...il.com>, Pavel Machek <pavel@...nel.org>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, Helge Deller <deller@....de>, 
 Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>, Liam Girdwood <lgirdwood@...il.com>, 
 Mark Brown <broonie@...nel.org>
Cc: dri-devel@...ts.freedesktop.org, linux-leds@...r.kernel.org, 
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-fbdev@...r.kernel.org, imx@...ts.linux.dev, 
 linux-arm-kernel@...ts.infradead.org, 
 Maud Spierings <maudspierings@...ontroll.com>
Subject: [PATCH v6 2/4] backlight: add max25014atg backlight

From: Maud Spierings <maudspierings@...ontroll.com>

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

Signed-off-by: Maud Spierings <maudspierings@...ontroll.com>
---
 MAINTAINERS                        |   1 +
 drivers/video/backlight/Kconfig    |   7 +
 drivers/video/backlight/Makefile   |   1 +
 drivers/video/backlight/max25014.c | 419 +++++++++++++++++++++++++++++++++++++
 4 files changed, 428 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 606ce086f758..d082d3f8cfae 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15265,6 +15265,7 @@ MAX25014 BACKLIGHT DRIVER
 M:	Maud Spierings <maudspierings@...ontroll.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@...log.com>
diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index d9374d208cee..d3bb6ccd4185 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 dfbb169bf6ea..1170d9ec40b8 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 000000000000..7000225752c3
--- /dev/null
+++ b/drivers/video/backlight/max25014.c
@@ -0,0 +1,419 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Backlight driver for Maxim MAX25014
+ *
+ * Copyright (C) 2025 GOcontroll B.V.
+ * Author: Maud Spierings <maudspierings@...ontroll.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_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;
+	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,
+};
+
+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_SHORT_GND, &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_SHORT_GND, &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;
+
+	/*
+	 * 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
+	 */
+	ret = regmap_read(maxim->regmap, MAX25014_DISABLE, &val);
+	if (ret)
+		return ret;
+
+	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;
+
+	ret = regmap_write(maxim->regmap, MAX25014_ISET,
+			   maxim->iset | MAX25014_ISET_ENA |
+			   MAX25014_ISET_PSEN);
+	return ret;
+}
+
+static int max25014_update_status(struct backlight_device *bl_dev)
+{
+	struct max25014 *maxim = bl_get_data(bl_dev);
+	uint32_t reg;
+	int ret;
+
+	if (backlight_is_blank(maxim->bl))
+		bl_dev->props.brightness = 0;
+
+	reg  = TON_STEP * bl_dev->props.brightness;
+
+	/*
+	 * 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;
+	struct fwnode_handle *child;
+	uint32_t strings[4];
+	int res, i;
+
+	if (!node)
+		return dev_err_probe(dev, -EINVAL, "no platform data\n");
+
+	child = device_get_next_child_node(dev, NULL);
+	if (child) {
+		res = fwnode_property_count_u32(child, "led-sources");
+		if (res > 0) {
+			fwnode_property_read_u32_array(child, "led-sources",
+						       strings, res);
+
+			/* set all strings as disabled, then enable those in led-sources*/
+			maxim->strings_mask = 0xf;
+			for (i = 0; i < res; i++) {
+				if (strings[i] <= 4)
+					maxim->strings_mask &= ~BIT(strings[i]);
+			}
+		}
+
+		fwnode_property_read_u32(child, "default-brightness",
+					 initial_brightness);
+
+		fwnode_handle_put(child);
+	}
+
+	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;
+
+	maxim->vin = devm_regulator_get(&maxim->client->dev, "power");
+	if (IS_ERR(maxim->vin)) {
+		return dev_err_probe(&maxim->client->dev, PTR_ERR(maxim->vin),
+				     "failed to get power-supply");
+	}
+
+	ret = regulator_enable(maxim->vin);
+	if (ret)
+		return dev_err_probe(&maxim->client->dev, ret,
+			"failed to enable power-supply\n");
+
+	maxim->enable = devm_gpiod_get_optional(&maxim->client->dev, "enable",
+						GPIOD_OUT_HIGH);
+	if (IS_ERR(maxim->enable)) {
+		ret = dev_err_probe(&maxim->client->dev, PTR_ERR(maxim->enable),
+				    "failed to get enable gpio\n");
+		goto disable_vin;
+	}
+
+	/* Datasheet Electrical Characteristics tSTARTUP 2ms */
+	fsleep(2000);
+
+	maxim->regmap = devm_regmap_init_i2c(cl, &max25014_regmap_config);
+	if (IS_ERR(maxim->regmap)) {
+		ret = dev_err_probe(&maxim->client->dev, PTR_ERR(maxim->regmap),
+			"failed to initialize the i2c regmap\n");
+		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_initial_power_state(maxim);
+	if (ret < 0) {
+		dev_err_probe(&maxim->client->dev, ret, "Could not get enabled state\n");
+		goto disable_full;
+	}
+
+	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) {
+		dev_err_probe(&maxim->client->dev, ret, "device config error");
+		goto disable_full;
+	}
+
+	bl = devm_backlight_device_register(&maxim->client->dev, id->name,
+					    &maxim->client->dev, maxim,
+					    &max25014_bl_ops, &props);
+	if (IS_ERR(bl)) {
+		ret = dev_err_probe(&maxim->client->dev, PTR_ERR(bl),
+				    "failed to register backlight\n");
+		goto disable_full;
+	}
+
+	maxim->bl = bl;
+
+	backlight_update_status(maxim->bl);
+
+	return 0;
+
+disable_full:
+	gpiod_set_value_cansleep(maxim->enable, 0);
+disable_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);
+	gpiod_set_value_cansleep(maxim->enable, 0);
+	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@...ontroll.com>");
+MODULE_LICENSE("GPL");

-- 
2.52.0

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