Message-Id: <20250725-max25014-v1-2-0e8cce92078e@gocontroll.com>
Date: Fri, 25 Jul 2025 13:09:24 +0200
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>
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>, 
 "Maud Spierings maudspierings"@gocontroll.com
Subject: [PATCH 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 intgrated boost controller.

Signed-off-by: Maud Spierings maudspierings@...ontroll.com
---
 MAINTAINERS                            |   2 +
 drivers/video/backlight/Kconfig        |   7 +
 drivers/video/backlight/Makefile       |   1 +
 drivers/video/backlight/max25014.c     | 449 +++++++++++++++++++++++++++++++++
 include/linux/platform_data/max25014.h |  24 ++
 5 files changed, 483 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 9e9a45442b7bf60b00eaf3f8ebadf8f4fbaf3bef..3cae3402f531921a93208626ba9477018e7ef347 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14911,6 +14911,8 @@ 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
+F:	include/linux/platform_data/max25014.h
 
 MAX31335 RTC DRIVER
 M:	Antoniu Miclaus <antoniu.miclaus@...log.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..371b6017953ae5955f4dfef921980dfdedd65d85
--- /dev/null
+++ b/drivers/video/backlight/max25014.c
@@ -0,0 +1,449 @@
+// 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/platform_data/max25014.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#define MAX25014_ISET_DEFAULT_100 11U
+#define MAX_BRIGHTNESS (100U)
+#define MIN_BRIGHTNESS (0U)
+#define TON_MAX (130720U) /* @153Hz */
+#define TON_STEP (1307U) /* @153Hz */
+#define TON_MIN (0U)
+
+#define MAX25014_DEV_ID         (0x00U)
+#define MAX25014_REV_ID         (0x01U)
+#define MAX25014_ISET           (0x02U)
+#define MAX25014_IMODE          (0x03U)
+#define MAX25014_TON1H          (0x04U)
+#define MAX25014_TON1L          (0x05U)
+#define MAX25014_TON2H          (0x06U)
+#define MAX25014_TON2L          (0x07U)
+#define MAX25014_TON3H          (0x08U)
+#define MAX25014_TON3L          (0x09U)
+#define MAX25014_TON4H          (0x0AU)
+#define MAX25014_TON4L          (0x0BU)
+#define MAX25014_TON_1_4_LSB    (0x0CU)
+#define MAX25014_SETTING        (0x12U)
+#define MAX25014_DISABLE        (0x13U)
+#define MAX25014_BSTMON         (0x14U)
+#define MAX25014_IOUT1          (0x15U)
+#define MAX25014_IOUT2          (0x16U)
+#define MAX25014_IOUT3          (0x17U)
+#define MAX25014_IOUT4          (0x18U)
+#define MAX25014_OPEN           (0x1BU)
+#define MAX25014_SHORT_GND      (0x1CU)
+#define MAX25014_SHORT_LED      (0x1DU)
+#define MAX25014_MASK           (0x1EU)
+#define MAX25014_DIAG           (0x1FU)
+
+#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 max25014 {
+	const char *chipname;
+	struct i2c_client *client;
+	struct backlight_device *bl;
+	struct device *dev;
+	struct regmap *regmap;
+	struct max25014_platform_data *pdata;
+	struct gpio_desc *enable;
+	struct regulator *vin; /* regulator for boost converter Vin rail */
+};
+
+static const struct regmap_config max25014_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = MAX25014_DIAG,
+};
+
+/**
+ * @brief get the bit mask for the DISABLE register.
+ *
+ * @param strings the led string configuration array.
+ * @return uint8_t bits to set in the register.
+ */
+static uint8_t strings_mask(struct max25014 *maxim)
+{
+	uint8_t res, i;
+
+	for (i = 0; i < 4; i++) {
+		if (maxim->pdata->strings[i] == 0)
+			res |= 1 << i;
+	}
+	return res;
+}
+
+/**
+ * @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->dev, "Open led strings detected on:\n");
+		for (i = 0; i < 4; i++) {
+			if (val & 1 << i)
+				dev_err(maxim->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->dev, "Short to ground detected on:\n");
+		for (i = 0; i < 4; i++) {
+			if (val & 1 << i)
+				dev_err(maxim->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->dev, "Shorted led detected on:\n");
+		for (i = 0; i < 4; i++) {
+			if (val & 1 << i)
+				dev_err(maxim->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->dev, "Overtemperature shutdown\n");
+		if (val & 0b10)
+			dev_warn(maxim->dev,
+				 "Chip is getting too hot (>125C)\n");
+		if (val & 0b1000)
+			dev_err(maxim->dev, "Boost converter overvoltage\n");
+		if (val & 0b10000)
+			dev_err(maxim->dev, "Boost converter undervoltage\n");
+		if (val & 0b100000)
+			dev_err(maxim->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)
+{
+	int ret;
+	uint32_t val;
+
+	ret = regmap_write(maxim->regmap, MAX25014_DISABLE,
+			   strings_mask(maxim));
+	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,
+				  maxim->pdata->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->pdata->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_backlight_register(struct max25014 *maxim)
+{
+	struct backlight_device *bl;
+	struct backlight_properties props;
+	struct max25014_platform_data *pdata = maxim->pdata;
+
+	memset(&props, 0, sizeof(props));
+	props.type = BACKLIGHT_PLATFORM;
+	props.max_brightness = MAX_BRIGHTNESS;
+
+	if (pdata->initial_brightness > props.max_brightness)
+		pdata->initial_brightness = props.max_brightness;
+
+	props.brightness = pdata->initial_brightness;
+
+	bl = devm_backlight_device_register(maxim->dev, maxim->chipname, maxim->dev,
+					    maxim, &max25014_bl_ops, &props);
+	if (IS_ERR(bl))
+		return PTR_ERR(bl);
+
+	maxim->bl = bl;
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static int max25014_parse_dt(struct max25014 *maxim)
+{
+	struct device *dev = maxim->dev;
+	struct device_node *node = dev->of_node;
+	struct max25014_platform_data *pdata;
+
+	int res;
+
+	if (!node) {
+		dev_err(dev, "no platform data\n");
+		return -EINVAL;
+	}
+
+	pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
+	if (!pdata)
+		return -ENOMEM;
+
+	res = of_property_count_u32_elems(node, "maxim,strings");
+	if (res == 4) {
+		of_property_read_u32_array(node, "maxim,strings", pdata->strings, 4);
+	} else {
+		dev_err(dev, "strings property not correctly defined\n");
+		return -EINVAL;
+	}
+
+	pdata->initial_brightness = 50U;
+	of_property_read_u32(node, "default-brightness", &pdata->initial_brightness);
+	pdata->iset = MAX25014_ISET_DEFAULT_100;
+	of_property_read_u32(node, "maxim,iset", &pdata->iset);
+
+	if (pdata->iset < 0 || pdata->iset > 15) {
+		dev_err(dev,
+			"Invalid iset, should be a value from 0-15, entered was %d\n",
+			pdata->iset);
+		return -EINVAL;
+	}
+
+	if (pdata->initial_brightness < 0 || pdata->initial_brightness > 100) {
+		dev_err(dev,
+			"Invalid initial brightness, should be a value from 0-100, entered was %d\n",
+			pdata->initial_brightness);
+		return -EINVAL;
+	}
+
+	maxim->pdata = pdata;
+
+	return 0;
+}
+#else
+static int max25014_parse_dt(struct max25014 *maxim)
+{
+	dev_err(maxim->dev,
+		"CONFIG_OF not configured, unable to parse devicetree");
+	return -EINVAL;
+}
+#endif
+
+static int max25014_probe(struct i2c_client *cl)
+{
+	const struct i2c_device_id *id = i2c_client_get_device_id(cl);
+	struct max25014 *maxim;
+	int ret;
+
+	maxim = devm_kzalloc(&cl->dev, sizeof(struct max25014), GFP_KERNEL);
+	if (!maxim)
+		return -ENOMEM;
+
+	maxim->client = cl;
+	maxim->dev = &cl->dev;
+	maxim->chipname = id->name;
+	maxim->pdata = dev_get_platdata(&cl->dev);
+
+	if (!maxim->pdata) {
+		ret = max25014_parse_dt(maxim);
+		if (ret < 0)
+			return ret;
+	}
+
+	maxim->vin = devm_regulator_get(maxim->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->dev, "failed to enable Vin: %d\n", ret);
+			return ret;
+		}
+	}
+
+	maxim->enable =
+		devm_gpiod_get_optional(maxim->dev, "enable", GPIOD_ASIS);
+	if (IS_ERR(maxim->enable)) {
+		ret = PTR_ERR(maxim->enable);
+		dev_err(maxim->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->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);
+	if (ret) {
+		dev_err(maxim->dev, "device config err: %d", ret);
+		goto disable_full;
+	}
+
+	ret = max25014_backlight_register(maxim);
+	if (ret) {
+		dev_err(maxim->dev, "failed to register backlight. err: %d\n",
+			ret);
+		goto disable_full;
+	}
+
+	dev_dbg(maxim->dev, "max25014 probed.\n");
+
+	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@...ontroll.com>");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/platform_data/max25014.h b/include/linux/platform_data/max25014.h
new file mode 100644
index 0000000000000000000000000000000000000000..048f11015e9551e619ddec9167e3f10394f44bb9
--- /dev/null
+++ b/include/linux/platform_data/max25014.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Backlight driver for Maxim MAX25014
+ *
+ * Copyright (C) 2025 GOcontroll B.V.
+ * Author: Maud Spierings <maudspierings@...ontroll.com>
+ */
+
+#ifndef _MAX25014_H
+#define _MAX25014_H
+
+/**
+ * struct max25014_platform_data
+ * @initial_brightness : Initial value of the backlight brightness.
+ * @iset : Value of the iset field which scales the amperage/limits it.
+ * @strings : Which, out of four, led strings are in use.
+ */
+struct max25014_platform_data {
+	uint32_t initial_brightness;
+	uint32_t iset;
+	uint32_t strings[4];
+};
+
+#endif

-- 
2.50.1

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