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 | 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@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 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@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_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@gocontroll.com>");
+MODULE_LICENSE("GPL");
--
2.52.0On Mon, Dec 01, 2025 at 12:53:21PM +0100, 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>
> <snip>
> +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);
Shouldn't this be MAX25014_SHORT_LED?
> + 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
> + */
Attach the comment to the if statement rather than the read.
> + 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;
This isn't right. Why would you change the backlight level just because
it is currently blanked (and sorry I missed this one last time).
> +
> + reg = TON_STEP * bl_dev->props.brightness;
The correct way to honour blanking is just go call
backlight_get_brightness() instead of reading the property directly.
> +
> + /*
> + * 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");
Can this use devm_regulator_get_enable()?
> +
> + 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);
Why is this needed? It was only ever set by devm_gpiod_get_optional().
> +disable_vin:
> + regulator_disable(maxim->vin);
This is also not needed if you use devm_regulator_get_enable().
> + return ret;
> +}
Daniel.
Thanks for the review.
On 12/4/25 17:17, Daniel Thompson wrote:
> On Mon, Dec 01, 2025 at 12:53:21PM +0100, 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>
>
>> <snip>
>
>> +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);
>
> Shouldn't this be MAX25014_SHORT_LED?
yep you are absolutely right
>
>> + 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
>> + */
>
> Attach the comment to the if statement rather than the read.
will do
>
>> + 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;
>
> This isn't right. Why would you change the backlight level just because
> it is currently blanked (and sorry I missed this one last time).
so just remove this bit then jeah?
>> +
>> + reg = TON_STEP * bl_dev->props.brightness;
>
> The correct way to honour blanking is just go call
> backlight_get_brightness() instead of reading the property directly.
will do.
>
>> +
>> + /*
>> + * 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");
>
> Can this use devm_regulator_get_enable()?
Yeah guess I'll just switch to that for now, if ever power management
gets implemented it can be figured out if regulator control is desired.
>
>> +
>> + 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);
>
> Why is this needed? It was only ever set by devm_gpiod_get_optional().
oops thats a leftover from before that change, good spot.
>> +disable_vin:
>> + regulator_disable(maxim->vin);
>
> This is also not needed if you use devm_regulator_get_enable().
jeah I'll drop this then too
kind regards,
Maud
On Fri, Dec 05, 2025 at 04:20:55PM +0100, Maud Spierings wrote:
> Thanks for the review.
>
> On 12/4/25 17:17, Daniel Thompson wrote:
> > On Mon, Dec 01, 2025 at 12:53:21PM +0100, Maud Spierings via B4 Relay wrote:
> > > The Maxim MAX25014 is a 4-channel automotive grade backlight driver IC
> > > with integrated boost controller.
> > >
> > > Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
>
> <snip>
>
> > > +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;
> >
> > This isn't right. Why would you change the backlight level just because
> > it is currently blanked (and sorry I missed this one last time).
>
> so just remove this bit then jeah?
Yes. backlight_get_brightness() is all you should need.
> > > +
> > > + reg = TON_STEP * bl_dev->props.brightness;
> >
> > The correct way to honour blanking is just go call
> > backlight_get_brightness() instead of reading the property directly.
>
> will do.
Thanks.
Daniel.
Do you have any comments about:
> +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);
> +}
I'm feeling like the setting of the brightness + update status maybe
should be a call to backlight_device_set_brightness() or maybe it
shouldn't really be there at all?
Kind regards,
Maud
On Fri, Jan 09, 2026 at 09:55:18AM +0100, Maud Spierings wrote:
> Do you have any comments about:
>
> > +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);
> > +}
>
> I'm feeling like the setting of the brightness + update status maybe should
> be a call to backlight_device_set_brightness() or maybe it shouldn't really
> be there at all?
Using backlight_device_set_brightness() makes sense (although there is
still a window where userspace could come back in and turn the backlight
on again). And, if both the GPIO and regulator were optional then it is
sensible to set the brightness to zero before removing the driver.
Daniel.
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