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

From: Krzysztof Kozlowski
Date: Tue Aug 29 2023 - 06:55:01 EST

On 29/08/2023 12:15, Flavio Suligoi wrote:
> 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

Why is this placed between LM and LP entries? Keep things ordered.

> + 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)

This should be just before probe function. It is part of probe path.

> +{
> + 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");

Drop

> + pdata->dimming_mode = DIMMING_PWM;
> + }
> + if (!strcmp(tmp_string, "analog-i2c")) {
> + dev_info(chip->dev, "dimming method: analog by I2C commands\n");

Drop


> + 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;

You miss constraints in the bindings.

> + 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;

return dev_err_probe()

> + }
> + 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 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),

sizeof(*)

> + 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");

Are you sure regmap allocation should be followed by error message?
Allocations must not... so if this is not allocation, then syntax is:

return dev_err_probe()

> + return ret;
> + }
> +
> + i2c_set_clientdata(client, chip);
> +
> + if (!pdata) {
> + pdata = devm_kzalloc(chip->dev,
> + sizeof(struct mp3309c_platform_data),

sizeof(*)

> + GFP_KERNEL);
> + if (!pdata)
> + return -ENOMEM;
> +
> + ret = pm3309c_parse_dt_node(chip, pdata);
> + if (ret) {
> + dev_err(&client->dev, "failed parsing DT node\n");

Why do you print errors multiple times? parse_dt_node already does it.

> + 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;

return dev_err_probe()

> + }
> +
> + /* 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);

return dev_err_probe()

> + }
> + 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);

return dev_err_probe()

> + }
> + 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");

Drop, not really helpful.

> + INIT_DELAYED_WORK(&chip->reset_gpio_work, mp3309c_reset_gpio);
> + }
> +
> + dev_info(&client->dev, "MP3309C backlight initialized");

Drop simple tracing messages.

> + 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);

Why do you need shutdown function?

> +}
> +
> +static const struct of_device_id mp3309c_match_table[] = {
> + { .compatible = "mps,mp3309c-backlight", },
> + { },
> +};
> +MODULE_DEVICE_TABLE(of, mp3309c_match_table);
> +


Best regards,
Krzysztof