[PATCH v1 2/2] backlight: mp3309c: Add support for MPS MP3309C

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The Monolithic Power (MPS) MP3309C is a WLED step-up converter, featuring a
programmable switching frequency to optimize efficiency.
The brightness can be controlled either by I2C commands (called "analog"
mode) or by a PWM input signal (PWM mode).
This driver supports both modes.

For DT configuration details, please refer to:
- Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yaml

The datasheet is available at:
- https://www.monolithicpower.com/en/mp3309c.html

Signed-off-by: Flavio Suligoi <f.suligoi@xxxxxxx>
---
 MAINTAINERS                          |   6 +
 drivers/video/backlight/Kconfig      |  13 +
 drivers/video/backlight/Makefile     |   1 +
 drivers/video/backlight/mp3309c_bl.c | 491 +++++++++++++++++++++++++++
 4 files changed, 511 insertions(+)
 create mode 100644 drivers/video/backlight/mp3309c_bl.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 3be1bdfe8ecc..895c56ff4f1e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14333,6 +14333,12 @@ S:	Maintained
 F:	Documentation/driver-api/tty/moxa-smartio.rst
 F:	drivers/tty/mxser.*
 
+MP3309C BACKLIGHT DRIVER
+M:	Flavio Suligoi <f.suligoi@xxxxxxx>
+S:	Maintained
+F:	Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yaml
+F:	drivers/video/backlight/mp3309c_bl.c
+
 MR800 AVERMEDIA USB FM RADIO DRIVER
 M:	Alexey Klimov <klimov.linux@xxxxxxxxx>
 L:	linux-media@xxxxxxxxxxxxxxx
diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 51387b1ef012..65d0ac9f611d 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -389,6 +389,19 @@ config BACKLIGHT_LM3639
 	help
 	  This supports TI LM3639 Backlight + 1.5A Flash LED Driver
 
+config BACKLIGHT_MP3309C
+	tristate "Backlight Driver for MPS MP3309C"
+	depends on I2C
+	select REGMAP_I2C
+	select NEW_LEDS
+	select LEDS_CLASS
+	help
+	  This supports MPS MP3309C backlight WLED Driver in both PWM and
+	  analog/I2C dimming modes.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called mp3309c_bl.
+
 config BACKLIGHT_LP855X
 	tristate "Backlight driver for TI LP855X"
 	depends on I2C && PWM
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index f72e1c3c59e9..c42c5bccc5ac 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -44,6 +44,7 @@ obj-$(CONFIG_BACKLIGHT_LP855X)		+= lp855x_bl.o
 obj-$(CONFIG_BACKLIGHT_LP8788)		+= lp8788_bl.o
 obj-$(CONFIG_BACKLIGHT_LV5207LP)	+= lv5207lp.o
 obj-$(CONFIG_BACKLIGHT_MAX8925)		+= max8925_bl.o
+obj-$(CONFIG_BACKLIGHT_MP3309C)		+= mp3309c_bl.o
 obj-$(CONFIG_BACKLIGHT_MT6370)		+= mt6370-backlight.o
 obj-$(CONFIG_BACKLIGHT_OMAP1)		+= omap1_bl.o
 obj-$(CONFIG_BACKLIGHT_PANDORA)		+= pandora_bl.o
diff --git a/drivers/video/backlight/mp3309c_bl.c b/drivers/video/backlight/mp3309c_bl.c
new file mode 100644
index 000000000000..7cb7a542ceca
--- /dev/null
+++ b/drivers/video/backlight/mp3309c_bl.c
@@ -0,0 +1,491 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Driver for MPS MP3309C White LED driver with I2C interface
+ *
+ * Copyright (C) 2023 ASEM Srl
+ * Author: Flavio Suligoi <f.suligoi@xxxxxxx>
+ */
+
+#include <linux/backlight.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/pwm.h>
+#include <linux/regmap.h>
+#include <linux/workqueue.h>
+
+#define REG_I2C_0	0x00
+#define REG_I2C_1	0x01
+
+#define REG_I2C_0_EN	0x80
+#define REG_I2C_0_D0	0x40
+#define REG_I2C_0_D1	0x20
+#define REG_I2C_0_D2	0x10
+#define REG_I2C_0_D3	0x08
+#define REG_I2C_0_D4	0x04
+#define REG_I2C_0_RSRV1	0x02
+#define REG_I2C_0_RSRV2	0x01
+
+#define REG_I2C_1_RSRV1	0x80
+#define REG_I2C_1_DIMS	0x40
+#define REG_I2C_1_SYNC	0x20
+#define REG_I2C_1_OVP0	0x10
+#define REG_I2C_1_OVP1	0x08
+#define REG_I2C_1_VOS	0x04
+#define REG_I2C_1_LEDO	0x02
+#define REG_I2C_1_OTP	0x01
+
+#define ANALOG_MAX_VAL	31
+#define ANALOG_REG_MASK 0x7c
+
+enum backlight_status {
+	FIRST_POWER_ON,
+	BACKLIGHT_OFF,
+	BACKLIGHT_ON,
+};
+
+enum dimming_mode_value {
+	DIMMING_PWM,
+	DIMMING_ANALOG_I2C,
+};
+
+struct mp3309c_platform_data {
+	u32 max_brightness;
+	u32 brightness;
+	u32 switch_on_delay_ms;
+	u32 switch_off_delay_ms;
+	u32 reset_on_delay_ms;
+	u32 reset_on_length_ms;
+	u8  dimming_mode;
+	u8  reset_pulse_enable;
+	u8  over_voltage_protection;
+
+	unsigned int status;
+};
+
+struct mp3309c_chip {
+	struct device *dev;
+	struct mp3309c_platform_data *pdata;
+	struct backlight_device *bl;
+	struct gpio_desc *enable_gpio;
+	struct regmap *regmap;
+	struct pwm_device *pwmd;
+
+	struct delayed_work enable_work;
+	struct delayed_work reset_gpio_work;
+	int irq;
+
+	struct gpio_desc *reset_gpio;
+};
+
+static const struct regmap_config mp3309c_regmap = {
+	.name = "mp3309c_regmap",
+	.reg_bits = 8,
+	.reg_stride = 1,
+	.val_bits = 8,
+	.max_register = REG_I2C_1,
+};
+
+static int pm3309c_parse_dt_node(struct mp3309c_chip *chip,
+				 struct mp3309c_platform_data *pdata)
+{
+	struct device_node *node = chip->dev->of_node;
+	const char *tmp_string;
+	int ret;
+
+	if (!node) {
+		dev_err(chip->dev, "failed to get DT node\n");
+		return -ENODEV;
+	}
+
+	/*
+	 * Dimming mode: the MP3309C provides two dimming methods:
+	 *
+	 * - PWM mode
+	 * - Analog by I2C control mode
+	 */
+	ret = of_property_read_string(node, "mps,dimming-mode", &tmp_string);
+	if (ret < 0) {
+		dev_err(chip->dev, "missed dimming-mode in DT\n");
+		return ret;
+	}
+	if (!strcmp(tmp_string, "pwm")) {
+		dev_info(chip->dev, "dimming method: PWM\n");
+		pdata->dimming_mode = DIMMING_PWM;
+	}
+	if (!strcmp(tmp_string, "analog-i2c")) {
+		dev_info(chip->dev, "dimming method: analog by I2C commands\n");
+		pdata->dimming_mode = DIMMING_ANALOG_I2C;
+	}
+
+	/* PWM steps (levels): 0 .. max_brightness */
+	ret = of_property_read_u32(node, "max-brightness",
+				   &pdata->max_brightness);
+	if (ret < 0) {
+		dev_err(chip->dev, "failed to get max-brightness from DT\n");
+		return ret;
+	}
+
+	/* Default brightness at startup */
+	ret = of_property_read_u32(node, "default-brightness",
+				   &pdata->brightness);
+	if (ret < 0) {
+		dev_err(chip->dev,
+			"failed to get default-brightness from DT\n");
+		return ret;
+	}
+
+	/*
+	 * Optional backlight switch-on/off delay
+	 *
+	 * Note: set 10ms as minimal value for switch-on delay, to stabilize
+	 *       video data
+	 */
+	pdata->switch_on_delay_ms = 50;
+	of_property_read_u32(node, "mps,switch-on-delay-ms",
+			     &pdata->switch_on_delay_ms);
+	if (pdata->switch_on_delay_ms < 10) {
+		pdata->switch_on_delay_ms = 10;
+		dev_warn(chip->dev,
+			 "switch-on-delay-ms set to 10ms as minimal value\n");
+	}
+	pdata->switch_off_delay_ms = 0;
+	of_property_read_u32(node, "mps,switch-off-delay-ms",
+			     &pdata->switch_off_delay_ms);
+
+	/*
+	 * Reset: GPIO, initial delay and pulse length
+	 *
+	 * Use this optional GPIO to reset an external device (LCD panel, video
+	 * FPGA, etc) when the backlight is switched on
+	 */
+	pdata->reset_pulse_enable = 0;
+	chip->reset_gpio = devm_gpiod_get_optional(chip->dev, "mps,reset",
+						   GPIOD_OUT_LOW);
+	if (IS_ERR(chip->reset_gpio)) {
+		ret = PTR_ERR(chip->reset_gpio);
+		dev_err(chip->dev, "error acquiring reset gpio: %d\n", ret);
+		return ret;
+	}
+	if (chip->reset_gpio) {
+		pdata->reset_pulse_enable = 1;
+
+		pdata->reset_on_delay_ms = 10;
+		of_property_read_u32(node, "mps,reset-on-delay-ms",
+				     &pdata->reset_on_delay_ms);
+		pdata->reset_on_length_ms = 10;
+		of_property_read_u32(node, "mps,reset-on-length-ms",
+				     &pdata->reset_on_length_ms);
+	}
+
+	/*
+	 * Over-voltage protection (OVP)
+	 *
+	 * These (optional) properties are:
+	 *
+	 *  - overvoltage-protection-13v --> OVP point set to 13.5V
+	 *  - overvoltage-protection-24v --> OVP point set to 24V
+	 *  - overvoltage-protection-35v --> OVP point set to 35.5V
+	 *
+	 * If not chosen, the hw default value for OVP is 35.5V
+	 */
+	pdata->over_voltage_protection = REG_I2C_1_OVP1;
+	if (of_property_read_bool(node, "mps,overvoltage-protection-13v"))
+		pdata->over_voltage_protection = 0x00;
+	if (of_property_read_bool(node, "mps,overvoltage-protection-24v"))
+		pdata->over_voltage_protection = REG_I2C_1_OVP0;
+	if (of_property_read_bool(node, "mps,overvoltage-protection-35v"))
+		pdata->over_voltage_protection = REG_I2C_1_OVP1;
+
+	return 0;
+}
+
+static int mp3309c_enable_device(struct mp3309c_chip *chip)
+{
+	u8 reg_val = 0; /* Configuration for analog by I2C commands */
+	int ret;
+
+	/* I2C register #0 - Device enable */
+	ret = regmap_update_bits(chip->regmap, REG_I2C_0, REG_I2C_0_EN,
+				 REG_I2C_0_EN);
+	if (ret)
+		return ret;
+
+	/*
+	 * I2C register #1 - Set working mode:
+	 *  - set one of the two dimming mode:
+	 *    - PWM dimming using an external PWM dimming signal
+	 *    - analog dimming using I2C commands
+	 *  - enable synchronous mode (fixed for now)
+	 *  - set overvoltage protection (OVP)
+	 */
+	if (chip->pdata->dimming_mode == DIMMING_PWM)
+		reg_val = REG_I2C_1_DIMS;
+	ret = regmap_write(chip->regmap, REG_I2C_1, reg_val | REG_I2C_1_SYNC |
+			   chip->pdata->over_voltage_protection);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+/* For delayed backlight enabled */
+static void mp3309c_enable(struct work_struct *work)
+{
+	struct mp3309c_chip *chip = container_of(work, struct mp3309c_chip,
+						 enable_work.work);
+	if (mp3309c_enable_device(chip))
+		dev_err(chip->dev, "failed writing I2C register\n");
+}
+
+static void mp3309c_reset_gpio(struct work_struct *work)
+{
+	struct mp3309c_chip *chip = container_of(work, struct mp3309c_chip,
+						 reset_gpio_work.work);
+
+	if (chip->reset_gpio) {
+		gpiod_set_value_cansleep(chip->reset_gpio, 0);
+		usleep_range(100, 150);
+		gpiod_set_value_cansleep(chip->reset_gpio, 1);
+		usleep_range(chip->pdata->reset_on_length_ms * 1000,
+			     (chip->pdata->reset_on_length_ms * 1000) + 100);
+		gpiod_set_value_cansleep(chip->reset_gpio, 0);
+	}
+}
+
+static int mp3309c_bl_update_status(struct backlight_device *bl)
+{
+	struct mp3309c_chip *chip = bl_get_data(bl);
+	int brightness = backlight_get_brightness(bl);
+	struct pwm_state pwmstate;
+	unsigned int analog_val, bits_val;
+	int i, ret;
+
+	if (chip->pdata->dimming_mode == DIMMING_PWM) {
+		/*
+		 * PWM dimming mode
+		 */
+		pwm_init_state(chip->pwmd, &pwmstate);
+		pwm_set_relative_duty_cycle(&pwmstate, brightness,
+					    chip->pdata->max_brightness);
+		pwmstate.enabled = true;
+		ret = pwm_apply_state(chip->pwmd, &pwmstate);
+		if (ret)
+			return ret;
+	} else {
+		/*
+		 * Analog dimming mode by I2C commands
+		 *
+		 * The 5 bits of the dimming analog value D4..D0 is allocated
+		 * in the I2C register #0, in the following way:
+		 *
+		 *     +--+--+--+--+--+--+--+--+
+		 *     |EN|D0|D1|D2|D3|D4|XX|XX|
+		 *     +--+--+--+--+--+--+--+--+
+		 */
+		analog_val = DIV_ROUND_UP(ANALOG_MAX_VAL * brightness,
+					  chip->pdata->max_brightness);
+		bits_val = 0;
+		for (i = 0; i <= 5; i++)
+			bits_val += ((analog_val >> i) & 0x01) << (6 - i);
+		ret = regmap_update_bits(chip->regmap, REG_I2C_0,
+					 ANALOG_REG_MASK, bits_val);
+		if (ret)
+			return ret;
+	}
+
+	if (brightness > 0) {
+		switch (chip->pdata->status) {
+		case FIRST_POWER_ON:
+			/*
+			 * Only for the first time, wait for the optional
+			 * switch-on delay and then enable the device.
+			 * Otherwise enable the backlight immediately.
+			 */
+			schedule_delayed_work(&chip->enable_work,
+					      msecs_to_jiffies(chip->pdata->switch_on_delay_ms));
+			/*
+			 * Optional external device GPIO reset, with
+			 * delay pulse length
+			 */
+			if (chip->pdata->reset_pulse_enable)
+				schedule_delayed_work(&chip->reset_gpio_work,
+						      msecs_to_jiffies(chip->pdata->reset_on_delay_ms));
+			break;
+		case BACKLIGHT_OFF:
+			/* Enable the backlight immediately */
+			if (chip->pdata->reset_pulse_enable)
+				cancel_delayed_work(&chip->reset_gpio_work);
+			mp3309c_enable_device(chip);
+			break;
+		}
+
+		chip->pdata->status = BACKLIGHT_ON;
+	} else {
+		/* Wait for the optional switch-off delay */
+		if (chip->pdata->switch_off_delay_ms > 0) {
+			usleep_range(chip->pdata->switch_off_delay_ms * 1000,
+				     (chip->pdata->switch_off_delay_ms + 1) *
+				      1000);
+		}
+
+		chip->pdata->status = BACKLIGHT_OFF;
+	}
+
+	return 0;
+}
+
+static const struct backlight_ops mp3309c_bl_ops = {
+	.update_status = mp3309c_bl_update_status,
+};
+
+static int mp3309c_probe(struct i2c_client *client)
+{
+	struct mp3309c_platform_data *pdata = dev_get_platdata(&client->dev);
+	struct mp3309c_chip *chip;
+	struct backlight_properties props;
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
+		dev_err(&client->dev, "failed to check i2c functionality\n");
+		return -EOPNOTSUPP;
+	}
+
+	chip = devm_kzalloc(&client->dev, sizeof(struct mp3309c_chip),
+			    GFP_KERNEL);
+	if (!chip)
+		return -ENOMEM;
+	chip->dev = &client->dev;
+
+	chip->regmap = devm_regmap_init_i2c(client, &mp3309c_regmap);
+	if (IS_ERR(chip->regmap)) {
+		ret = PTR_ERR(chip->regmap);
+		dev_err(&client->dev, "failed to allocate register map\n");
+		return ret;
+	}
+
+	i2c_set_clientdata(client, chip);
+
+	if (!pdata) {
+		pdata = devm_kzalloc(chip->dev,
+				     sizeof(struct mp3309c_platform_data),
+				     GFP_KERNEL);
+		if (!pdata)
+			return -ENOMEM;
+
+		ret = pm3309c_parse_dt_node(chip, pdata);
+		if (ret) {
+			dev_err(&client->dev, "failed parsing DT node\n");
+			return ret;
+		}
+	}
+	chip->pdata = pdata;
+
+	chip->enable_gpio = devm_gpiod_get_optional(&client->dev, "enable",
+						    GPIOD_OUT_HIGH);
+	if (IS_ERR(chip->enable_gpio)) {
+		ret = PTR_ERR(chip->enable_gpio);
+		return ret;
+	}
+
+	/* Backlight */
+	props.type = BACKLIGHT_RAW;
+	props.brightness = pdata->brightness;
+	props.max_brightness = pdata->max_brightness;
+	props.scale = BACKLIGHT_SCALE_LINEAR;
+	chip->bl =
+	    devm_backlight_device_register(chip->dev, "mp3309c_bl",
+					   chip->dev, chip, &mp3309c_bl_ops,
+					   &props);
+	if (IS_ERR(chip->bl)) {
+		dev_err(&client->dev, "failed registering backlight\n");
+		return PTR_ERR(chip->bl);
+	}
+	pdata->status = FIRST_POWER_ON;
+
+	/* Enable PWM, if required */
+	if (pdata->dimming_mode == DIMMING_PWM) {
+		chip->pwmd = devm_pwm_get(chip->dev, NULL);
+		if (IS_ERR(chip->pwmd)) {
+			dev_err(&client->dev, "failed getting pwm device\n");
+			return PTR_ERR(chip->pwmd);
+		}
+		pwm_apply_args(chip->pwmd);
+	}
+
+	/*
+	 * Workqueue for delayed backlight enabling
+	 */
+	INIT_DELAYED_WORK(&chip->enable_work, mp3309c_enable);
+
+	/*
+	 * Workqueue for (optional) external device GPIO reset
+	 */
+	if (pdata->reset_pulse_enable) {
+		dev_info(&client->dev, "reset pulse enabled\n");
+		INIT_DELAYED_WORK(&chip->reset_gpio_work, mp3309c_reset_gpio);
+	}
+
+	dev_info(&client->dev, "MP3309C backlight initialized");
+	return 0;
+}
+
+static int mp3309c_backlight_switch_off(struct pwm_device *pwmd)
+{
+	struct pwm_state pwmstate;
+
+	/* Switch-off the backlight */
+	pwm_get_state(pwmd, &pwmstate);
+	pwmstate.duty_cycle = 0;
+	pwmstate.enabled = false;
+	pwm_apply_state(pwmd, &pwmstate);
+
+	return 0;
+}
+
+static void mp3309c_remove(struct i2c_client *client)
+{
+	struct mp3309c_chip *chip = i2c_get_clientdata(client);
+
+	if (chip->pdata->dimming_mode == DIMMING_PWM)
+		mp3309c_backlight_switch_off(chip->pwmd);
+	if (chip->pdata->reset_pulse_enable)
+		cancel_delayed_work(&chip->reset_gpio_work);
+}
+
+static void mp3309c_shutdown(struct i2c_client *client)
+{
+	struct mp3309c_chip *chip = i2c_get_clientdata(client);
+
+	if (chip->pdata->dimming_mode == DIMMING_PWM)
+		mp3309c_backlight_switch_off(chip->pwmd);
+}
+
+static const struct of_device_id mp3309c_match_table[] = {
+	{ .compatible = "mps,mp3309c-backlight", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, mp3309c_match_table);
+
+static const struct i2c_device_id mp3309c_id[] = {
+	{ "mp3309c", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, mp3309c_id);
+
+static struct i2c_driver mp3309c_i2c_driver = {
+	.driver	= {
+			.name		= "mp3309c-backlight",
+			.of_match_table	= mp3309c_match_table,
+	},
+	.probe		= mp3309c_probe,
+	.remove		= mp3309c_remove,
+	.shutdown	= mp3309c_shutdown,
+	.id_table	= mp3309c_id,
+};
+
+module_i2c_driver(mp3309c_i2c_driver);
+
+MODULE_DESCRIPTION("Backlight Driver for MPS MP3309C");
+MODULE_AUTHOR("Flavio Suligoi <f.suligoi@xxxxxxx>");
+MODULE_LICENSE("GPL");
-- 
2.34.1




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