Re: [PATCH v5 08/11] leds: rgb: add support for Samsung S2M series PMIC RGB LED device

[Lee Jones <lee@kernel.org>]

On Fri, 24 Apr 2026, Kaustabh Chakraborty wrote:

> Add support for the RGB LEDs found in certain Samsung S2M series PMICs.
> The device has three LED channels, controlled as a single device. These
> LEDs are typically used as status indicators in mobile phones.
> 
> The driver includes initial support for the S2MU005 PMIC RGB LEDs.
> 
> Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
> ---
>  drivers/leds/rgb/Kconfig        |  11 +
>  drivers/leds/rgb/Makefile       |   1 +
>  drivers/leds/rgb/leds-s2m-rgb.c | 446 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 458 insertions(+)
> 
> diff --git a/drivers/leds/rgb/Kconfig b/drivers/leds/rgb/Kconfig
> index 28ef4c487367c..30051342f4e4d 100644
> --- a/drivers/leds/rgb/Kconfig
> +++ b/drivers/leds/rgb/Kconfig
> @@ -75,6 +75,17 @@ config LEDS_QCOM_LPG
>  
>  	  If compiled as a module, the module will be named leds-qcom-lpg.
>  
> +config LEDS_S2M_RGB
> +	tristate "Samsung S2M series PMICs RGB LED support"
> +	depends on LEDS_CLASS
> +	depends on MFD_SEC_CORE
> +	select REGMAP_IRQ
> +	help
> +	  This option enables support for the S2MU005 RGB LEDs. These
> +	  devices have three LED channels, with 8-bit brightness control
> +	  for each channel. It's usually found in mobile phones as

"The S2MU005 is ..."

> +	  status indicators.
> +
>  config LEDS_MT6370_RGB
>  	tristate "LED Support for MediaTek MT6370 PMIC"
>  	depends on MFD_MT6370
> diff --git a/drivers/leds/rgb/Makefile b/drivers/leds/rgb/Makefile
> index be45991f63f50..98050e1aa4255 100644
> --- a/drivers/leds/rgb/Makefile
> +++ b/drivers/leds/rgb/Makefile
> @@ -6,4 +6,5 @@ obj-$(CONFIG_LEDS_LP5812)		+= leds-lp5812.o
>  obj-$(CONFIG_LEDS_NCP5623)		+= leds-ncp5623.o
>  obj-$(CONFIG_LEDS_PWM_MULTICOLOR)	+= leds-pwm-multicolor.o
>  obj-$(CONFIG_LEDS_QCOM_LPG)		+= leds-qcom-lpg.o
> +obj-$(CONFIG_LEDS_S2M_RGB)		+= leds-s2m-rgb.o
>  obj-$(CONFIG_LEDS_MT6370_RGB)		+= leds-mt6370-rgb.o
> diff --git a/drivers/leds/rgb/leds-s2m-rgb.c b/drivers/leds/rgb/leds-s2m-rgb.c
> new file mode 100644
> index 0000000000000..51d12f2ef762a
> --- /dev/null
> +++ b/drivers/leds/rgb/leds-s2m-rgb.c
> @@ -0,0 +1,446 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * RGB LED Driver for Samsung S2M series PMICs.
> + *
> + * Copyright (c) 2015 Samsung Electronics Co., Ltd
> + * Copyright (c) 2026 Kaustabh Chakraborty <kauschluss@disroot.org>
> + */
> +
> +#include <linux/container_of.h>
> +#include <linux/led-class-multicolor.h>
> +#include <linux/mfd/samsung/core.h>
> +#include <linux/mfd/samsung/s2mu005.h>
> +#include <linux/minmax.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +
> +struct s2m_rgb {
> +	struct device *dev;
> +	struct regmap *regmap;
> +	struct led_classdev_mc mc;
> +	enum sec_device_type device_type;
> +	/*
> +	 * The mutex object prevents race conditions when evaluation and
> +	 * application of LED pattern state.
> +	 */
> +	struct mutex lock;
> +	/*
> +	 * State variables representing the current LED pattern, these only to
> +	 * be accessed when lock is held.
> +	 */
> +	u8 ramp_up;
> +	u8 ramp_dn;
> +	u8 stay_hi;
> +	u8 stay_lo;
> +};
> +
> +static struct led_classdev_mc *to_s2m_mc(struct led_classdev *cdev)
> +{
> +	return container_of(cdev, struct led_classdev_mc, led_cdev);
> +}
> +
> +static struct s2m_rgb *to_s2m_rgb(struct led_classdev_mc *mc)
> +{
> +	return container_of(mc, struct s2m_rgb, mc);
> +}
> +
> +static const u32 s2mu005_rgb_lut_ramp[] = {
> +	0,	100,	200,	300,	400,	500,	600,	700,
> +	800,	1000,	1200,	1400,	1600,	1800,	2000,	2200,
> +};
> +
> +static const u32 s2mu005_rgb_lut_stay_hi[] = {
> +	100,	200,	300,	400,	500,	750,	1000,	1250,
> +	1500,	1750,	2000,	2250,	2500,	2750,	3000,	3250,
> +};
> +
> +static const u32 s2mu005_rgb_lut_stay_lo[] = {
> +	0,	500,	1000,	1500,	2000,	2500,	3000,	3500,
> +	4000,	4500,	5000,	6000,	7000,	8000,	10000,	12000,
> +};
> +
> +static int s2mu005_rgb_apply_params(struct s2m_rgb *rgb)
> +{
> +	struct regmap *regmap = rgb->regmap;
> +	unsigned int ramp_val = 0;
> +	unsigned int stay_val = 0;
> +	int ret;
> +	int i;
> +
> +	ramp_val |= FIELD_PREP(S2MU005_RGB_CH_RAMP_UP, rgb->ramp_up);
> +	ramp_val |= FIELD_PREP(S2MU005_RGB_CH_RAMP_DN, rgb->ramp_dn);
> +
> +	stay_val |= FIELD_PREP(S2MU005_RGB_CH_STAY_HI, rgb->stay_hi);
> +	stay_val |= FIELD_PREP(S2MU005_RGB_CH_STAY_LO, rgb->stay_lo);
> +
> +	ret = regmap_write(regmap, S2MU005_REG_RGB_EN, S2MU005_RGB_RESET);
> +	if (ret < 0) {
> +		dev_err(rgb->dev, "failed to reset RGB LEDs\n");
> +		return ret;
> +	}
> +
> +	for (i = 0; i < rgb->mc.num_colors; i++) {

for (int i = 0; ...)

> +		ret = regmap_write(regmap, S2MU005_REG_RGB_CH_CTRL(i),
> +				   rgb->mc.subled_info[i].brightness);
> +		if (ret < 0) {
> +			dev_err(rgb->dev, "failed to set LED brightness\n");
> +			return ret;
> +		}
> +
> +		ret = regmap_write(regmap, S2MU005_REG_RGB_CH_RAMP(i), ramp_val);
> +		if (ret < 0) {
> +			dev_err(rgb->dev, "failed to set ramp timings\n");
> +			return ret;
> +		}
> +
> +		ret = regmap_write(regmap, S2MU005_REG_RGB_CH_STAY(i), stay_val);
> +		if (ret < 0) {
> +			dev_err(rgb->dev, "failed to set stay timings\n");
> +			return ret;
> +		}
> +	}
> +
> +	ret = regmap_update_bits(regmap, S2MU005_REG_RGB_EN, S2MU005_RGB_SLOPE,
> +				 S2MU005_RGB_SLOPE_SMOOTH);
> +	if (ret < 0) {
> +		dev_err(rgb->dev, "failed to set ramp slope\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int s2mu005_rgb_reset_params(struct s2m_rgb *rgb)
> +{
> +	struct regmap *regmap = rgb->regmap;
> +	int ret;
> +
> +	ret = regmap_write(regmap, S2MU005_REG_RGB_EN, S2MU005_RGB_RESET);
> +	if (ret < 0) {
> +		dev_err(rgb->dev, "failed to reset RGB LEDs\n");
> +		return ret;
> +	}
> +
> +	rgb->ramp_up = 0;
> +	rgb->ramp_dn = 0;
> +	rgb->stay_hi = 0;
> +	rgb->stay_lo = 0;
> +
> +	return 0;
> +}
> +
> +static int s2m_rgb_lut_calc_timing(const u32 *lut, const size_t len,
> +				   const u32 req_time, u8 *idx)
> +{
> +	int lo = 0;
> +	int hi = len - 2;
> +
> +	/* Bounds checking */
> +	if (req_time < lut[0] || req_time > lut[len - 1])
> +		return -EINVAL;
> +
> +	/*
> +	 * Perform a binary search to pick the best timing from the LUT.
> +	 *
> +	 * The search algorithm picks two consecutive elements of the
> +	 * LUT and tries to search the pair between which the requested
> +	 * time lies.
> +	 */
> +	while (lo <= hi) {
> +		*idx = (lo + hi) / 2;
> +
> +		if ((lut[*idx] <= req_time) && (req_time <= lut[*idx + 1]))
> +			break;
> +
> +		if ((req_time < lut[*idx]) && (req_time < lut[*idx + 1]))
> +			hi = *idx - 1;
> +		else
> +			lo = *idx + 1;
> +	}
> +
> +	/*
> +	 * The searched timing is always less than the requested time. At
> +	 * times, the succeeding timing in the LUT is closer thus more
> +	 * accurate. Adjust the resulting value if that's the case.
> +	 */
> +	if (abs(req_time - lut[*idx]) > abs(lut[*idx + 1] - req_time))
> +		(*idx)++;

As much as I appreciate the comments, most of the function is pretty
unreadable.  Are you able to use better variable nomenclature and layout
to better describe your aims?

> +	return 0;
> +}
> +
> +static int s2m_rgb_pattern_set(struct led_classdev *cdev, struct led_pattern *pattern,
> +			       u32 len, int repeat)
> +{
> +	struct s2m_rgb *rgb = to_s2m_rgb(to_s2m_mc(cdev));
> +	const u32 *lut_ramp_up, *lut_ramp_dn, *lut_stay_hi, *lut_stay_lo;
> +	size_t lut_ramp_up_len, lut_ramp_dn_len, lut_stay_hi_len, lut_stay_lo_len;
> +	int brightness_peak = 0;
> +	u32 time_hi = 0, time_lo = 0;
> +	bool ramp_up_en, ramp_dn_en;
> +	int ret;
> +	int i;
> +
> +	/*
> +	 * The typical pattern supported by this device can be
> +	 * represented with the following graph:
> +	 *
> +	 *  255 T ''''''-.                         .-'''''''-.
> +	 *      |         '.                     .'           '.
> +	 *      |           \                   /               \
> +	 *      |            '.               .'                 '.
> +	 *      |              '-...........-'                     '-
> +	 *    0 +----------------------------------------------------> time (s)
> +	 *
> +	 *       <---- HIGH ----><-- LOW --><-------- HIGH --------->
> +	 *       <-----><-------><---------><-------><-----><------->
> +	 *       stay_hi ramp_dn   stay_lo   ramp_up stay_hi ramp_dn
> +	 *
> +	 * There are two states, named HIGH and LOW. HIGH has a non-zero
> +	 * brightness level, while LOW is of zero brightness. The
> +	 * pattern provided should mention only one zero and non-zero
> +	 * brightness level. The hardware always starts the pattern from
> +	 * the HIGH state, as shown in the graph.
> +	 *
> +	 * The HIGH state can be divided in three somewhat equal timings:
> +	 * ramp_up, stay_hi, and ramp_dn. The LOW state has only one
> +	 * timing: stay_lo.
> +	 */
> +
> +	/* Only indefinitely looping patterns are supported. */
> +	if (repeat != -1)
> +		return -EINVAL;
> +
> +	/* Pattern should consist of at least two tuples. */
> +	if (len < 2)
> +		return -EINVAL;
> +
> +	for (i = 0; i < len; i++) {

for (int i = 0; ...) would be preferable.

> +		int brightness = pattern[i].brightness;
> +		u32 delta_t = pattern[i].delta_t;
> +
> +		if (brightness) {
> +			/*
> +			 * The pattern shold define only one non-zero
> +			 * brightness in the HIGH state. The device
> +			 * doesn't have any provisions to handle
> +			 * multiple peak brightness levels.
> +			 */
> +			if (brightness_peak && brightness_peak != brightness)
> +				return -EINVAL;
> +
> +			brightness_peak = brightness;
> +			time_hi += delta_t;
> +			ramp_dn_en = !!delta_t;
> +		} else {
> +			time_lo += delta_t;
> +			ramp_up_en = !!delta_t;
> +		}
> +	}
> +
> +	switch (rgb->device_type) {
> +	case S2MU005:
> +		lut_ramp_up = s2mu005_rgb_lut_ramp;
> +		lut_ramp_up_len = ARRAY_SIZE(s2mu005_rgb_lut_ramp);
> +		lut_ramp_dn = s2mu005_rgb_lut_ramp;
> +		lut_ramp_dn_len = ARRAY_SIZE(s2mu005_rgb_lut_ramp);
> +		lut_stay_hi = s2mu005_rgb_lut_stay_hi;
> +		lut_stay_hi_len = ARRAY_SIZE(s2mu005_rgb_lut_stay_hi);
> +		lut_stay_lo = s2mu005_rgb_lut_stay_lo;
> +		lut_stay_lo_len = ARRAY_SIZE(s2mu005_rgb_lut_stay_lo);
> +		break;
> +	default:
> +		/* execution shouldn't reach here */

Instead of a comment, perhaps a WARN_ON_ONCE(1); or similar would be
more robust here to catch unexpected device types?

> +		break;
> +	}
> +
> +	mutex_lock(&rgb->lock);
> +
> +	/*
> +	 * The timings ramp_up, stay_hi, and ramp_dn of the HIGH state
> +	 * are roughly equal. Firstly, calculate and set timings for
> +	 * ramp_up and ramp_dn (making sure they're exactly equal).
> +	 */
> +	rgb->ramp_up = 0;
> +	rgb->ramp_dn = 0;
> +
> +	if (ramp_up_en) {
> +		ret = s2m_rgb_lut_calc_timing(lut_ramp_up, lut_ramp_up_len, time_hi / 3,
> +					      &rgb->ramp_up);
> +		if (ret < 0)
> +			goto param_fail;
> +	}
> +
> +	if (ramp_dn_en) {
> +		ret = s2m_rgb_lut_calc_timing(lut_ramp_dn, lut_ramp_dn_len, time_hi / 3,
> +					      &rgb->ramp_dn);
> +		if (ret < 0)
> +			goto param_fail;
> +	}
> +
> +	/*
> +	 * Subtract the allocated ramp timings from time_hi (and also
> +	 * making sure it doesn't underflow!). The remaining time is
> +	 * allocated to stay_hi.
> +	 */
> +	time_hi -= min(time_hi, lut_ramp_up[rgb->ramp_up]);
> +	time_hi -= min(time_hi, lut_ramp_dn[rgb->ramp_dn]);
> +
> +	ret = s2m_rgb_lut_calc_timing(lut_stay_hi, lut_stay_hi_len, time_hi, &rgb->stay_hi);
> +	if (ret < 0)
> +		goto param_fail;
> +
> +	ret = s2m_rgb_lut_calc_timing(lut_stay_lo, lut_stay_lo_len, time_lo, &rgb->stay_lo);
> +	if (ret < 0)
> +		goto param_fail;
> +
> +	led_mc_calc_color_components(&rgb->mc, brightness_peak);
> +	switch (rgb->device_type) {
> +	case S2MU005:
> +		ret = s2mu005_rgb_apply_params(rgb);
> +		break;
> +	default:
> +		/* execution shouldn't reach here */
> +		break;
> +	}
> +	if (ret < 0)
> +		goto param_fail;

Are we expecting positive values in these 'ret's?

If not if (!ret) will do.

> +
> +	mutex_unlock(&rgb->lock);
> +
> +	return 0;
> +
> +param_fail:
> +	rgb->ramp_up = 0;
> +	rgb->ramp_dn = 0;
> +	rgb->stay_hi = 0;
> +	rgb->stay_lo = 0;
> +
> +	mutex_unlock(&rgb->lock);
> +
> +	return ret;
> +}
> +
> +static int s2m_rgb_pattern_clear(struct led_classdev *cdev)
> +{
> +	struct s2m_rgb *rgb = to_s2m_rgb(to_s2m_mc(cdev));
> +	int ret = 0;
> +
> +	mutex_lock(&rgb->lock);
> +
> +	switch (rgb->device_type) {
> +	case S2MU005:
> +		ret = s2mu005_rgb_reset_params(rgb);
> +		break;
> +	default:
> +		/* execution shouldn't reach here */
> +		break;

As above.

And a single branch switch () makes little sense.

> +	}
> +
> +	mutex_unlock(&rgb->lock);
> +
> +	return ret;
> +}
> +
> +static int s2m_rgb_brightness_set(struct led_classdev *cdev, enum led_brightness value)
> +{
> +	struct s2m_rgb *rgb = to_s2m_rgb(to_s2m_mc(cdev));
> +	int ret = 0;
> +
> +	if (!value)
> +		return s2m_rgb_pattern_clear(cdev);
> +
> +	mutex_lock(&rgb->lock);
> +
> +	led_mc_calc_color_components(&rgb->mc, value);
> +	switch (rgb->device_type) {
> +	case S2MU005:
> +		ret = s2mu005_rgb_apply_params(rgb);
> +		break;
> +	default:
> +		/* execution shouldn't reach here */
> +		break;
> +	}
> +
> +	mutex_unlock(&rgb->lock);
> +
> +	return ret;
> +}
> +
> +static struct mc_subled s2mu005_rgb_subled_info[] = {

const?

> +	{ .channel = 0, .color_index = LED_COLOR_ID_BLUE },
> +	{ .channel = 1, .color_index = LED_COLOR_ID_GREEN },
> +	{ .channel = 2, .color_index = LED_COLOR_ID_RED },
> +};
> +
> +static int s2m_rgb_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct sec_pmic_dev *pmic_drvdata = dev_get_drvdata(dev->parent);
> +	struct s2m_rgb *rgb;
> +	struct led_init_data init_data = {};
> +	int ret;
> +
> +	rgb = devm_kzalloc(dev, sizeof(*rgb), GFP_KERNEL);
> +	if (!rgb)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, rgb);
> +	rgb->dev = dev;
> +	rgb->regmap = pmic_drvdata->regmap_pmic;
> +	rgb->device_type = platform_get_device_id(pdev)->driver_data;

We don't tend to use these object oriented-type constructs in the
kernel.  Also, we have helper functions of extracting driver_data.
Please use them.

> +
> +	switch (rgb->device_type) {
> +	case S2MU005:
> +		rgb->mc.subled_info = s2mu005_rgb_subled_info;
> +		rgb->mc.num_colors = ARRAY_SIZE(s2mu005_rgb_subled_info);
> +		break;
> +	default:
> +		return dev_err_probe(dev, -ENODEV, "device type %d is not supported by driver\n",
> +				     pmic_drvdata->device_type);

Small point, but for consistency, would it be better to print
`rgb->device_type` here, since that is the value being checked in the
switch statement?

Also, same single branch comment as before.

> +	}
> +
> +	rgb->mc.led_cdev.max_brightness = 255;
> +	rgb->mc.led_cdev.brightness_set_blocking = s2m_rgb_brightness_set;
> +	rgb->mc.led_cdev.pattern_set = s2m_rgb_pattern_set;
> +	rgb->mc.led_cdev.pattern_clear = s2m_rgb_pattern_clear;
> +
> +	ret = devm_mutex_init(dev, &rgb->lock);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "failed to create mutex lock\n");
> +
> +	init_data.fwnode = of_fwnode_handle(dev->of_node);
> +	ret = devm_led_classdev_multicolor_register_ext(dev, &rgb->mc, &init_data);
> +	if (ret < 0)
> +		return dev_err_probe(dev, ret, "failed to create LED device\n");
> +
> +	return 0;
> +}
> +
> +static const struct platform_device_id s2m_rgb_id_table[] = {
> +	{ "s2mu005-rgb", S2MU005 },
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(platform, s2m_rgb_id_table);
> +
> +static const struct of_device_id s2m_rgb_of_match_table[] = {
> +	{ .compatible = "samsung,s2mu005-rgb", .data = (void *)S2MU005 },
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, s2m_rgb_of_match_table);
> +
> +static struct platform_driver s2m_rgb_driver = {
> +	.driver = {
> +		.name = "s2m-rgb",
> +	},
> +	.probe = s2m_rgb_probe,
> +	.id_table = s2m_rgb_id_table,
> +};
> +module_platform_driver(s2m_rgb_driver);
> +
> +MODULE_DESCRIPTION("RGB LED Driver For Samsung S2M Series PMICs");

"for"

> +MODULE_AUTHOR("Kaustabh Chakraborty <kauschluss@disroot.org>");
> +MODULE_LICENSE("GPL");

-- 
Lee Jones