// SPDX-License-Identifier: GPL-2.0-only /* * Backlight driver for Maxim MAX25014 * * Copyright (C) 2025 GOcontroll B.V. * Author: Maud Spierings */ #include #include #include #include #include #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_SHORTGND 0x1C #define MAX25014_SHORTED_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; 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_SHORTGND, &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_SHORTED_LED, &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; ret = regmap_read(maxim->regmap, MAX25014_DISABLE, &val); if (ret) return 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 */ 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; return regmap_write(maxim->regmap, MAX25014_ISET, maxim->iset | MAX25014_ISET_ENA | MAX25014_ISET_PSEN); } static int max25014_update_status(struct backlight_device *bl_dev) { struct max25014 *maxim = bl_get_data(bl_dev); uint32_t reg; int ret; reg = TON_STEP * backlight_get_brightness(bl_dev); /* * 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; uint32_t strings[4]; int res, i; res = of_property_count_u32_elems(node, "maxim,strings"); if (res == 4) { of_property_read_u32_array(node, "maxim,strings", strings, 4); for (i = 0; i < 4; i++) { if (strings[i] == 0) maxim->strings_mask |= 1 << i; } } else { maxim->strings_mask = 0; } *initial_brightness = 50U; of_property_read_u32(node, "default-brightness", initial_brightness); 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; ret = devm_regulator_get_enable(&maxim->client->dev, "power"); if (ret) return dev_err_probe(&maxim->client->dev, ret, "failed to get power-supply"); maxim->enable = devm_gpiod_get_optional(&maxim->client->dev, "enable", GPIOD_OUT_HIGH); if (IS_ERR(maxim->enable)) return dev_err_probe(&maxim->client->dev, PTR_ERR(maxim->enable), "failed to get enable gpio\n"); /* Datasheet Electrical Characteristics tSTARTUP 2ms */ fsleep(2000); maxim->regmap = devm_regmap_init_i2c(cl, &max25014_regmap_config); if (IS_ERR(maxim->regmap)) return dev_err_probe(&maxim->client->dev, PTR_ERR(maxim->regmap), "failed to initialize the i2c regmap\n"); i2c_set_clientdata(cl, maxim); ret = max25014_check_errors(maxim); if (ret) /* error is already reported in the above function */ return ret; ret = max25014_initial_power_state(maxim); if (ret < 0) return dev_err_probe(&maxim->client->dev, ret, "Could not get enabled state\n"); 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) return dev_err_probe(&maxim->client->dev, ret, "device config error"); bl = devm_backlight_device_register(&maxim->client->dev, id->name, &maxim->client->dev, maxim, &max25014_bl_ops, &props); if (IS_ERR(bl)) return dev_err_probe(&maxim->client->dev, PTR_ERR(bl), "failed to register backlight\n"); maxim->bl = bl; backlight_update_status(maxim->bl); return 0; } static void max25014_remove(struct i2c_client *cl) { struct max25014 *maxim = i2c_get_clientdata(cl); backlight_device_set_brightness(maxim->bl, 0); gpiod_set_value_cansleep(maxim->enable, 0); } 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 "); MODULE_LICENSE("GPL");