drivers/video/backlight/pm8941-wled.c - linux - Git at Google

 /* Copyright (c) 2015, Sony Mobile Communications, AB.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 and
  * only version 2 as published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  */

 #include <linux/kernel.h>
 #include <linux/backlight.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/regmap.h>

 /* From DT binding */
 #define PM8941_WLED_DEFAULT_BRIGHTNESS		2048

 #define PM8941_WLED_REG_VAL_BASE		0x40
 #define  PM8941_WLED_REG_VAL_MAX		0xFFF

 #define PM8941_WLED_REG_MOD_EN			0x46
 #define  PM8941_WLED_REG_MOD_EN_BIT		BIT(7)
 #define  PM8941_WLED_REG_MOD_EN_MASK		BIT(7)

 #define PM8941_WLED_REG_SYNC			0x47
 #define  PM8941_WLED_REG_SYNC_MASK		0x07
 #define  PM8941_WLED_REG_SYNC_LED1		BIT(0)
 #define  PM8941_WLED_REG_SYNC_LED2		BIT(1)
 #define  PM8941_WLED_REG_SYNC_LED3		BIT(2)
 #define  PM8941_WLED_REG_SYNC_ALL		0x07
 #define  PM8941_WLED_REG_SYNC_CLEAR		0x00

 #define PM8941_WLED_REG_FREQ			0x4c
 #define  PM8941_WLED_REG_FREQ_MASK		0x0f

 #define PM8941_WLED_REG_OVP			0x4d
 #define  PM8941_WLED_REG_OVP_MASK		0x03

 #define PM8941_WLED_REG_BOOST			0x4e
 #define  PM8941_WLED_REG_BOOST_MASK		0x07

 #define PM8941_WLED_REG_SINK			0x4f
 #define  PM8941_WLED_REG_SINK_MASK		0xe0
 #define  PM8941_WLED_REG_SINK_SHFT		0x05

 /* Per-'string' registers below */
 #define PM8941_WLED_REG_STR_OFFSET		0x10

 #define PM8941_WLED_REG_STR_MOD_EN_BASE		0x60
 #define  PM8941_WLED_REG_STR_MOD_MASK		BIT(7)
 #define  PM8941_WLED_REG_STR_MOD_EN		BIT(7)

 #define PM8941_WLED_REG_STR_SCALE_BASE		0x62
 #define  PM8941_WLED_REG_STR_SCALE_MASK		0x1f

 #define PM8941_WLED_REG_STR_MOD_SRC_BASE	0x63
 #define  PM8941_WLED_REG_STR_MOD_SRC_MASK	0x01
 #define  PM8941_WLED_REG_STR_MOD_SRC_INT	0x00
 #define  PM8941_WLED_REG_STR_MOD_SRC_EXT	0x01

 #define PM8941_WLED_REG_STR_CABC_BASE		0x66
 #define  PM8941_WLED_REG_STR_CABC_MASK		BIT(7)
 #define  PM8941_WLED_REG_STR_CABC_EN		BIT(7)

 struct pm8941_wled_config {
 	u32 i_boost_limit;
 	u32 ovp;
 	u32 switch_freq;
 	u32 num_strings;
 	u32 i_limit;
 	bool cs_out_en;
 	bool ext_gen;
 	bool cabc_en;
 };

 struct pm8941_wled {
 	const char *name;
 	struct regmap *regmap;
 	u16 addr;

 	struct pm8941_wled_config cfg;
 };

 static int pm8941_wled_update_status(struct backlight_device *bl)
 {
 	struct pm8941_wled *wled = bl_get_data(bl);
 	u16 val = bl->props.brightness;
 	u8 ctrl = 0;
 	int rc;
 	int i;

 	if (bl->props.power != FB_BLANK_UNBLANK ||
 	    bl->props.fb_blank != FB_BLANK_UNBLANK ||
 	    bl->props.state & BL_CORE_FBBLANK)
 		val = 0;

 	if (val != 0)
 		ctrl = PM8941_WLED_REG_MOD_EN_BIT;

 	rc = regmap_update_bits(wled->regmap,
 			wled->addr + PM8941_WLED_REG_MOD_EN,
 			PM8941_WLED_REG_MOD_EN_MASK, ctrl);
 	if (rc)
 		return rc;

 	for (i = 0; i < wled->cfg.num_strings; ++i) {
 		u8 v[2] = { val & 0xff, (val >> 8) & 0xf };

 		rc = regmap_bulk_write(wled->regmap,
 				wled->addr + PM8941_WLED_REG_VAL_BASE + 2 * i,
 				v, 2);
 		if (rc)
 			return rc;
 	}

 	rc = regmap_update_bits(wled->regmap,
 			wled->addr + PM8941_WLED_REG_SYNC,
 			PM8941_WLED_REG_SYNC_MASK, PM8941_WLED_REG_SYNC_ALL);
 	if (rc)
 		return rc;

 	rc = regmap_update_bits(wled->regmap,
 			wled->addr + PM8941_WLED_REG_SYNC,
 			PM8941_WLED_REG_SYNC_MASK, PM8941_WLED_REG_SYNC_CLEAR);
 	return rc;
 }

 static int pm8941_wled_setup(struct pm8941_wled *wled)
 {
 	int rc;
 	int i;

 	rc = regmap_update_bits(wled->regmap,
 			wled->addr + PM8941_WLED_REG_OVP,
 			PM8941_WLED_REG_OVP_MASK, wled->cfg.ovp);
 	if (rc)
 		return rc;

 	rc = regmap_update_bits(wled->regmap,
 			wled->addr + PM8941_WLED_REG_BOOST,
 			PM8941_WLED_REG_BOOST_MASK, wled->cfg.i_boost_limit);
 	if (rc)
 		return rc;

 	rc = regmap_update_bits(wled->regmap,
 			wled->addr + PM8941_WLED_REG_FREQ,
 			PM8941_WLED_REG_FREQ_MASK, wled->cfg.switch_freq);
 	if (rc)
 		return rc;

 	if (wled->cfg.cs_out_en) {
 		u8 all = (BIT(wled->cfg.num_strings) - 1)
 				<< PM8941_WLED_REG_SINK_SHFT;

 		rc = regmap_update_bits(wled->regmap,
 				wled->addr + PM8941_WLED_REG_SINK,
 				PM8941_WLED_REG_SINK_MASK, all);
 		if (rc)
 			return rc;
 	}

 	for (i = 0; i < wled->cfg.num_strings; ++i) {
 		u16 addr = wled->addr + PM8941_WLED_REG_STR_OFFSET * i;

 		rc = regmap_update_bits(wled->regmap,
 				addr + PM8941_WLED_REG_STR_MOD_EN_BASE,
 				PM8941_WLED_REG_STR_MOD_MASK,
 				PM8941_WLED_REG_STR_MOD_EN);
 		if (rc)
 			return rc;

 		if (wled->cfg.ext_gen) {
 			rc = regmap_update_bits(wled->regmap,
 					addr + PM8941_WLED_REG_STR_MOD_SRC_BASE,
 					PM8941_WLED_REG_STR_MOD_SRC_MASK,
 					PM8941_WLED_REG_STR_MOD_SRC_EXT);
 			if (rc)
 				return rc;
 		}

 		rc = regmap_update_bits(wled->regmap,
 				addr + PM8941_WLED_REG_STR_SCALE_BASE,
 				PM8941_WLED_REG_STR_SCALE_MASK,
 				wled->cfg.i_limit);
 		if (rc)
 			return rc;

 		rc = regmap_update_bits(wled->regmap,
 				addr + PM8941_WLED_REG_STR_CABC_BASE,
 				PM8941_WLED_REG_STR_CABC_MASK,
 				wled->cfg.cabc_en ?
 					PM8941_WLED_REG_STR_CABC_EN : 0);
 		if (rc)
 			return rc;
 	}

 	return 0;
 }

 static const struct pm8941_wled_config pm8941_wled_config_defaults = {
 	.i_boost_limit = 3,
 	.i_limit = 20,
 	.ovp = 2,
 	.switch_freq = 5,
 	.num_strings = 0,
 	.cs_out_en = false,
 	.ext_gen = false,
 	.cabc_en = false,
 };

 struct pm8941_wled_var_cfg {
 	const u32 *values;
 	u32 (*fn)(u32);
 	int size;
 };

 static const u32 pm8941_wled_i_boost_limit_values[] = {
 	105, 385, 525, 805, 980, 1260, 1400, 1680,
 };

 static const struct pm8941_wled_var_cfg pm8941_wled_i_boost_limit_cfg = {
 	.values = pm8941_wled_i_boost_limit_values,
 	.size = ARRAY_SIZE(pm8941_wled_i_boost_limit_values),
 };

 static const u32 pm8941_wled_ovp_values[] = {
 	35, 32, 29, 27,
 };

 static const struct pm8941_wled_var_cfg pm8941_wled_ovp_cfg = {
 	.values = pm8941_wled_ovp_values,
 	.size = ARRAY_SIZE(pm8941_wled_ovp_values),
 };

 static u32 pm8941_wled_num_strings_values_fn(u32 idx)
 {
 	return idx + 1;
 }

 static const struct pm8941_wled_var_cfg pm8941_wled_num_strings_cfg = {
 	.fn = pm8941_wled_num_strings_values_fn,
 	.size = 3,
 };

 static u32 pm8941_wled_switch_freq_values_fn(u32 idx)
 {
 	return 19200 / (2 * (1 + idx));
 }

 static const struct pm8941_wled_var_cfg pm8941_wled_switch_freq_cfg = {
 	.fn = pm8941_wled_switch_freq_values_fn,
 	.size = 16,
 };

 static const struct pm8941_wled_var_cfg pm8941_wled_i_limit_cfg = {
 	.size = 26,
 };

 static u32 pm8941_wled_values(const struct pm8941_wled_var_cfg *cfg, u32 idx)
 {
 	if (idx >= cfg->size)
 		return UINT_MAX;
 	if (cfg->fn)
 		return cfg->fn(idx);
 	if (cfg->values)
 		return cfg->values[idx];
 	return idx;
 }

 static int pm8941_wled_configure(struct pm8941_wled *wled, struct device *dev)
 {
 	struct pm8941_wled_config *cfg = &wled->cfg;
 	u32 val;
 	int rc;
 	u32 c;
 	int i;
 	int j;

 	const struct {
 		const char *name;
 		u32 *val_ptr;
 		const struct pm8941_wled_var_cfg *cfg;
 	} u32_opts[] = {
 		{
 			"qcom,current-boost-limit",
 			&cfg->i_boost_limit,
 			.cfg = &pm8941_wled_i_boost_limit_cfg,
 		},
 		{
 			"qcom,current-limit",
 			&cfg->i_limit,
 			.cfg = &pm8941_wled_i_limit_cfg,
 		},
 		{
 			"qcom,ovp",
 			&cfg->ovp,
 			.cfg = &pm8941_wled_ovp_cfg,
 		},
 		{
 			"qcom,switching-freq",
 			&cfg->switch_freq,
 			.cfg = &pm8941_wled_switch_freq_cfg,
 		},
 		{
 			"qcom,num-strings",
 			&cfg->num_strings,
 			.cfg = &pm8941_wled_num_strings_cfg,
 		},
 	};
 	const struct {
 		const char *name;
 		bool *val_ptr;
 	} bool_opts[] = {
 		{ "qcom,cs-out", &cfg->cs_out_en, },
 		{ "qcom,ext-gen", &cfg->ext_gen, },
 		{ "qcom,cabc", &cfg->cabc_en, },
 	};

 	rc = of_property_read_u32(dev->of_node, "reg", &val);
 	if (rc || val > 0xffff) {
 		dev_err(dev, "invalid IO resources\n");
 		return rc ? rc : -EINVAL;
 	}
 	wled->addr = val;

 	rc = of_property_read_string(dev->of_node, "label", &wled->name);
 	if (rc)
 		wled->name = devm_kasprintf(dev, GFP_KERNEL, "%pOFn", dev->of_node);

 	*cfg = pm8941_wled_config_defaults;
 	for (i = 0; i < ARRAY_SIZE(u32_opts); ++i) {
 		rc = of_property_read_u32(dev->of_node, u32_opts[i].name, &val);
 		if (rc == -EINVAL) {
 			continue;
 		} else if (rc) {
 			dev_err(dev, "error reading '%s'\n", u32_opts[i].name);
 			return rc;
 		}

 		c = UINT_MAX;
 		for (j = 0; c != val; j++) {
 			c = pm8941_wled_values(u32_opts[i].cfg, j);
 			if (c == UINT_MAX) {
 				dev_err(dev, "invalid value for '%s'\n",
 					u32_opts[i].name);
 				return -EINVAL;
 			}
 		}

 		dev_dbg(dev, "'%s' = %u\n", u32_opts[i].name, c);
 		*u32_opts[i].val_ptr = j;
 	}

 	for (i = 0; i < ARRAY_SIZE(bool_opts); ++i) {
 		if (of_property_read_bool(dev->of_node, bool_opts[i].name))
 			*bool_opts[i].val_ptr = true;
 	}

 	cfg->num_strings = cfg->num_strings + 1;

 	return 0;
 }

 static const struct backlight_ops pm8941_wled_ops = {
 	.update_status = pm8941_wled_update_status,
 };

 static int pm8941_wled_probe(struct platform_device *pdev)
 {
 	struct backlight_properties props;
 	struct backlight_device *bl;
 	struct pm8941_wled *wled;
 	struct regmap *regmap;
 	u32 val;
 	int rc;

 	regmap = dev_get_regmap(pdev->dev.parent, NULL);
 	if (!regmap) {
 		dev_err(&pdev->dev, "Unable to get regmap\n");
 		return -EINVAL;
 	}

 	wled = devm_kzalloc(&pdev->dev, sizeof(*wled), GFP_KERNEL);
 	if (!wled)
 		return -ENOMEM;

 	wled->regmap = regmap;

 	rc = pm8941_wled_configure(wled, &pdev->dev);
 	if (rc)
 		return rc;

 	rc = pm8941_wled_setup(wled);
 	if (rc)
 		return rc;

 	val = PM8941_WLED_DEFAULT_BRIGHTNESS;
 	of_property_read_u32(pdev->dev.of_node, "default-brightness", &val);

 	memset(&props, 0, sizeof(struct backlight_properties));
 	props.type = BACKLIGHT_RAW;
 	props.brightness = val;
 	props.max_brightness = PM8941_WLED_REG_VAL_MAX;
 	bl = devm_backlight_device_register(&pdev->dev, wled->name,
 					    &pdev->dev, wled,
 					    &pm8941_wled_ops, &props);
 	return PTR_ERR_OR_ZERO(bl);
 };

 static const struct of_device_id pm8941_wled_match_table[] = {
 	{ .compatible = "qcom,pm8941-wled" },
 	{}
 };
 MODULE_DEVICE_TABLE(of, pm8941_wled_match_table);

 static struct platform_driver pm8941_wled_driver = {
 	.probe = pm8941_wled_probe,
 	.driver	= {
 		.name = "pm8941-wled",
 		.of_match_table	= pm8941_wled_match_table,
 	},
 };

 module_platform_driver(pm8941_wled_driver);

 MODULE_DESCRIPTION("pm8941 wled driver");
 MODULE_LICENSE("GPL v2");
	/* Copyright (c) 2015, Sony Mobile Communications, AB.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 and
	* only version 2 as published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*/

	#include <linux/kernel.h>
	#include <linux/backlight.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/of_device.h>
	#include <linux/regmap.h>

	/* From DT binding */
	#define PM8941_WLED_DEFAULT_BRIGHTNESS 2048

	#define PM8941_WLED_REG_VAL_BASE 0x40
	#define PM8941_WLED_REG_VAL_MAX 0xFFF

	#define PM8941_WLED_REG_MOD_EN 0x46
	#define PM8941_WLED_REG_MOD_EN_BIT BIT(7)
	#define PM8941_WLED_REG_MOD_EN_MASK BIT(7)

	#define PM8941_WLED_REG_SYNC 0x47
	#define PM8941_WLED_REG_SYNC_MASK 0x07
	#define PM8941_WLED_REG_SYNC_LED1 BIT(0)
	#define PM8941_WLED_REG_SYNC_LED2 BIT(1)
	#define PM8941_WLED_REG_SYNC_LED3 BIT(2)
	#define PM8941_WLED_REG_SYNC_ALL 0x07
	#define PM8941_WLED_REG_SYNC_CLEAR 0x00

	#define PM8941_WLED_REG_FREQ 0x4c
	#define PM8941_WLED_REG_FREQ_MASK 0x0f

	#define PM8941_WLED_REG_OVP 0x4d
	#define PM8941_WLED_REG_OVP_MASK 0x03

	#define PM8941_WLED_REG_BOOST 0x4e
	#define PM8941_WLED_REG_BOOST_MASK 0x07

	#define PM8941_WLED_REG_SINK 0x4f
	#define PM8941_WLED_REG_SINK_MASK 0xe0
	#define PM8941_WLED_REG_SINK_SHFT 0x05

	/* Per-'string' registers below */
	#define PM8941_WLED_REG_STR_OFFSET 0x10

	#define PM8941_WLED_REG_STR_MOD_EN_BASE 0x60
	#define PM8941_WLED_REG_STR_MOD_MASK BIT(7)
	#define PM8941_WLED_REG_STR_MOD_EN BIT(7)

	#define PM8941_WLED_REG_STR_SCALE_BASE 0x62
	#define PM8941_WLED_REG_STR_SCALE_MASK 0x1f

	#define PM8941_WLED_REG_STR_MOD_SRC_BASE 0x63
	#define PM8941_WLED_REG_STR_MOD_SRC_MASK 0x01
	#define PM8941_WLED_REG_STR_MOD_SRC_INT 0x00
	#define PM8941_WLED_REG_STR_MOD_SRC_EXT 0x01

	#define PM8941_WLED_REG_STR_CABC_BASE 0x66
	#define PM8941_WLED_REG_STR_CABC_MASK BIT(7)
	#define PM8941_WLED_REG_STR_CABC_EN BIT(7)

	struct pm8941_wled_config {
	u32 i_boost_limit;
	u32 ovp;
	u32 switch_freq;
	u32 num_strings;
	u32 i_limit;
	bool cs_out_en;
	bool ext_gen;
	bool cabc_en;
	};

	struct pm8941_wled {
	const char *name;
	struct regmap *regmap;
	u16 addr;

	struct pm8941_wled_config cfg;
	};

	static int pm8941_wled_update_status(struct backlight_device *bl)
	{
	struct pm8941_wled *wled = bl_get_data(bl);
	u16 val = bl->props.brightness;
	u8 ctrl = 0;
	int rc;
	int i;

	if (bl->props.power != FB_BLANK_UNBLANK \|\|
	bl->props.fb_blank != FB_BLANK_UNBLANK \|\|
	bl->props.state & BL_CORE_FBBLANK)
	val = 0;

	if (val != 0)
	ctrl = PM8941_WLED_REG_MOD_EN_BIT;

	rc = regmap_update_bits(wled->regmap,
	wled->addr + PM8941_WLED_REG_MOD_EN,
	PM8941_WLED_REG_MOD_EN_MASK, ctrl);
	if (rc)
	return rc;

	for (i = 0; i < wled->cfg.num_strings; ++i) {
	u8 v[2] = { val & 0xff, (val >> 8) & 0xf };

	rc = regmap_bulk_write(wled->regmap,
	wled->addr + PM8941_WLED_REG_VAL_BASE + 2 * i,
	v, 2);
	if (rc)
	return rc;
	}

	rc = regmap_update_bits(wled->regmap,
	wled->addr + PM8941_WLED_REG_SYNC,
	PM8941_WLED_REG_SYNC_MASK, PM8941_WLED_REG_SYNC_ALL);
	if (rc)
	return rc;

	rc = regmap_update_bits(wled->regmap,
	wled->addr + PM8941_WLED_REG_SYNC,
	PM8941_WLED_REG_SYNC_MASK, PM8941_WLED_REG_SYNC_CLEAR);
	return rc;
	}

	static int pm8941_wled_setup(struct pm8941_wled *wled)
	{
	int rc;
	int i;

	rc = regmap_update_bits(wled->regmap,
	wled->addr + PM8941_WLED_REG_OVP,
	PM8941_WLED_REG_OVP_MASK, wled->cfg.ovp);
	if (rc)
	return rc;

	rc = regmap_update_bits(wled->regmap,
	wled->addr + PM8941_WLED_REG_BOOST,
	PM8941_WLED_REG_BOOST_MASK, wled->cfg.i_boost_limit);
	if (rc)
	return rc;

	rc = regmap_update_bits(wled->regmap,
	wled->addr + PM8941_WLED_REG_FREQ,
	PM8941_WLED_REG_FREQ_MASK, wled->cfg.switch_freq);
	if (rc)
	return rc;

	if (wled->cfg.cs_out_en) {
	u8 all = (BIT(wled->cfg.num_strings) - 1)
	<< PM8941_WLED_REG_SINK_SHFT;

	rc = regmap_update_bits(wled->regmap,
	wled->addr + PM8941_WLED_REG_SINK,
	PM8941_WLED_REG_SINK_MASK, all);
	if (rc)
	return rc;
	}

	for (i = 0; i < wled->cfg.num_strings; ++i) {
	u16 addr = wled->addr + PM8941_WLED_REG_STR_OFFSET * i;

	rc = regmap_update_bits(wled->regmap,
	addr + PM8941_WLED_REG_STR_MOD_EN_BASE,
	PM8941_WLED_REG_STR_MOD_MASK,
	PM8941_WLED_REG_STR_MOD_EN);
	if (rc)
	return rc;

	if (wled->cfg.ext_gen) {
	rc = regmap_update_bits(wled->regmap,
	addr + PM8941_WLED_REG_STR_MOD_SRC_BASE,
	PM8941_WLED_REG_STR_MOD_SRC_MASK,
	PM8941_WLED_REG_STR_MOD_SRC_EXT);
	if (rc)
	return rc;
	}

	rc = regmap_update_bits(wled->regmap,
	addr + PM8941_WLED_REG_STR_SCALE_BASE,
	PM8941_WLED_REG_STR_SCALE_MASK,
	wled->cfg.i_limit);
	if (rc)
	return rc;

	rc = regmap_update_bits(wled->regmap,
	addr + PM8941_WLED_REG_STR_CABC_BASE,
	PM8941_WLED_REG_STR_CABC_MASK,
	wled->cfg.cabc_en ?
	PM8941_WLED_REG_STR_CABC_EN : 0);
	if (rc)
	return rc;
	}

	return 0;
	}

	static const struct pm8941_wled_config pm8941_wled_config_defaults = {
	.i_boost_limit = 3,
	.i_limit = 20,
	.ovp = 2,
	.switch_freq = 5,
	.num_strings = 0,
	.cs_out_en = false,
	.ext_gen = false,
	.cabc_en = false,
	};

	struct pm8941_wled_var_cfg {
	const u32 *values;
	u32 (*fn)(u32);
	int size;
	};

	static const u32 pm8941_wled_i_boost_limit_values[] = {
	105, 385, 525, 805, 980, 1260, 1400, 1680,
	};

	static const struct pm8941_wled_var_cfg pm8941_wled_i_boost_limit_cfg = {
	.values = pm8941_wled_i_boost_limit_values,
	.size = ARRAY_SIZE(pm8941_wled_i_boost_limit_values),
	};

	static const u32 pm8941_wled_ovp_values[] = {
	35, 32, 29, 27,
	};

	static const struct pm8941_wled_var_cfg pm8941_wled_ovp_cfg = {
	.values = pm8941_wled_ovp_values,
	.size = ARRAY_SIZE(pm8941_wled_ovp_values),
	};

	static u32 pm8941_wled_num_strings_values_fn(u32 idx)
	{
	return idx + 1;
	}

	static const struct pm8941_wled_var_cfg pm8941_wled_num_strings_cfg = {
	.fn = pm8941_wled_num_strings_values_fn,
	.size = 3,
	};

	static u32 pm8941_wled_switch_freq_values_fn(u32 idx)
	{
	return 19200 / (2 * (1 + idx));
	}

	static const struct pm8941_wled_var_cfg pm8941_wled_switch_freq_cfg = {
	.fn = pm8941_wled_switch_freq_values_fn,
	.size = 16,
	};

	static const struct pm8941_wled_var_cfg pm8941_wled_i_limit_cfg = {
	.size = 26,
	};

	static u32 pm8941_wled_values(const struct pm8941_wled_var_cfg *cfg, u32 idx)
	{
	if (idx >= cfg->size)
	return UINT_MAX;
	if (cfg->fn)
	return cfg->fn(idx);
	if (cfg->values)
	return cfg->values[idx];
	return idx;
	}

	static int pm8941_wled_configure(struct pm8941_wled wled, struct device dev)
	{
	struct pm8941_wled_config *cfg = &wled->cfg;
	u32 val;
	int rc;
	u32 c;
	int i;
	int j;

	const struct {
	const char *name;
	u32 *val_ptr;
	const struct pm8941_wled_var_cfg *cfg;
	} u32_opts[] = {
	{
	"qcom,current-boost-limit",
	&cfg->i_boost_limit,
	.cfg = &pm8941_wled_i_boost_limit_cfg,
	},
	{
	"qcom,current-limit",
	&cfg->i_limit,
	.cfg = &pm8941_wled_i_limit_cfg,
	},
	{
	"qcom,ovp",
	&cfg->ovp,
	.cfg = &pm8941_wled_ovp_cfg,
	},
	{
	"qcom,switching-freq",
	&cfg->switch_freq,
	.cfg = &pm8941_wled_switch_freq_cfg,
	},
	{
	"qcom,num-strings",
	&cfg->num_strings,
	.cfg = &pm8941_wled_num_strings_cfg,
	},
	};
	const struct {
	const char *name;
	bool *val_ptr;
	} bool_opts[] = {
	{ "qcom,cs-out", &cfg->cs_out_en, },
	{ "qcom,ext-gen", &cfg->ext_gen, },
	{ "qcom,cabc", &cfg->cabc_en, },
	};

	rc = of_property_read_u32(dev->of_node, "reg", &val);
	if (rc \|\| val > 0xffff) {
	dev_err(dev, "invalid IO resources\n");
	return rc ? rc : -EINVAL;
	}
	wled->addr = val;

	rc = of_property_read_string(dev->of_node, "label", &wled->name);
	if (rc)
	wled->name = devm_kasprintf(dev, GFP_KERNEL, "%pOFn", dev->of_node);

	*cfg = pm8941_wled_config_defaults;
	for (i = 0; i < ARRAY_SIZE(u32_opts); ++i) {
	rc = of_property_read_u32(dev->of_node, u32_opts[i].name, &val);
	if (rc == -EINVAL) {
	continue;
	} else if (rc) {
	dev_err(dev, "error reading '%s'\n", u32_opts[i].name);
	return rc;
	}

	c = UINT_MAX;
	for (j = 0; c != val; j++) {
	c = pm8941_wled_values(u32_opts[i].cfg, j);
	if (c == UINT_MAX) {
	dev_err(dev, "invalid value for '%s'\n",
	u32_opts[i].name);
	return -EINVAL;
	}
	}

	dev_dbg(dev, "'%s' = %u\n", u32_opts[i].name, c);
	*u32_opts[i].val_ptr = j;
	}

	for (i = 0; i < ARRAY_SIZE(bool_opts); ++i) {
	if (of_property_read_bool(dev->of_node, bool_opts[i].name))
	*bool_opts[i].val_ptr = true;
	}

	cfg->num_strings = cfg->num_strings + 1;

	return 0;
	}

	static const struct backlight_ops pm8941_wled_ops = {
	.update_status = pm8941_wled_update_status,
	};

	static int pm8941_wled_probe(struct platform_device *pdev)
	{
	struct backlight_properties props;
	struct backlight_device *bl;
	struct pm8941_wled *wled;
	struct regmap *regmap;
	u32 val;
	int rc;

	regmap = dev_get_regmap(pdev->dev.parent, NULL);
	if (!regmap) {
	dev_err(&pdev->dev, "Unable to get regmap\n");
	return -EINVAL;
	}

	wled = devm_kzalloc(&pdev->dev, sizeof(*wled), GFP_KERNEL);
	if (!wled)
	return -ENOMEM;

	wled->regmap = regmap;

	rc = pm8941_wled_configure(wled, &pdev->dev);
	if (rc)
	return rc;

	rc = pm8941_wled_setup(wled);
	if (rc)
	return rc;

	val = PM8941_WLED_DEFAULT_BRIGHTNESS;
	of_property_read_u32(pdev->dev.of_node, "default-brightness", &val);

	memset(&props, 0, sizeof(struct backlight_properties));
	props.type = BACKLIGHT_RAW;
	props.brightness = val;
	props.max_brightness = PM8941_WLED_REG_VAL_MAX;
	bl = devm_backlight_device_register(&pdev->dev, wled->name,
	&pdev->dev, wled,
	&pm8941_wled_ops, &props);
	return PTR_ERR_OR_ZERO(bl);
	};

	static const struct of_device_id pm8941_wled_match_table[] = {
	{ .compatible = "qcom,pm8941-wled" },
	{}
	};
	MODULE_DEVICE_TABLE(of, pm8941_wled_match_table);

	static struct platform_driver pm8941_wled_driver = {
	.probe = pm8941_wled_probe,
	.driver = {
	.name = "pm8941-wled",
	.of_match_table = pm8941_wled_match_table,
	},
	};

	module_platform_driver(pm8941_wled_driver);

	MODULE_DESCRIPTION("pm8941 wled driver");
	MODULE_LICENSE("GPL v2");