1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Backlight driver for Maxim MAX25014 4 * 5 * Copyright (C) 2025 GOcontroll B.V. 6 * Author: Maud Spierings <maudspierings@gocontroll.com> 7 */ 8 9 #include <linux/backlight.h> 10 #include <linux/gpio/consumer.h> 11 #include <linux/i2c.h> 12 #include <linux/regmap.h> 13 #include <linux/slab.h> 14 15 #define MAX25014_ISET_DEFAULT_100 11 16 #define MAX_BRIGHTNESS 100 17 #define MIN_BRIGHTNESS 0 18 #define TON_MAX 130720 /* @153Hz */ 19 #define TON_STEP 1307 /* @153Hz */ 20 #define TON_MIN 0 21 22 #define MAX25014_DEV_ID 0x00 23 #define MAX25014_REV_ID 0x01 24 #define MAX25014_ISET 0x02 25 #define MAX25014_IMODE 0x03 26 #define MAX25014_TON1H 0x04 27 #define MAX25014_TON1L 0x05 28 #define MAX25014_TON2H 0x06 29 #define MAX25014_TON2L 0x07 30 #define MAX25014_TON3H 0x08 31 #define MAX25014_TON3L 0x09 32 #define MAX25014_TON4H 0x0A 33 #define MAX25014_TON4L 0x0B 34 #define MAX25014_TON_1_4_LSB 0x0C 35 #define MAX25014_SETTING 0x12 36 #define MAX25014_DISABLE 0x13 37 #define MAX25014_BSTMON 0x14 38 #define MAX25014_IOUT1 0x15 39 #define MAX25014_IOUT2 0x16 40 #define MAX25014_IOUT3 0x17 41 #define MAX25014_IOUT4 0x18 42 #define MAX25014_OPEN 0x1B 43 #define MAX25014_SHORTGND 0x1C 44 #define MAX25014_SHORTED_LED 0x1D 45 #define MAX25014_MASK 0x1E 46 #define MAX25014_DIAG 0x1F 47 48 #define MAX25014_ISET_ENA BIT(5) 49 #define MAX25014_ISET_PSEN BIT(4) 50 #define MAX25014_IMODE_HDIM BIT(2) 51 #define MAX25014_SETTING_FPWM GENMASK(6, 4) 52 #define MAX25014_DISABLE_DIS_MASK GENMASK(3, 0) 53 #define MAX25014_DIAG_OT BIT(0) 54 #define MAX25014_DIAG_OTW BIT(1) 55 #define MAX25014_DIAG_HW_RST BIT(2) 56 #define MAX25014_DIAG_BSTOV BIT(3) 57 #define MAX25014_DIAG_BSTUV BIT(4) 58 #define MAX25014_DIAG_IREFOOR BIT(5) 59 60 struct max25014 { 61 struct i2c_client *client; 62 struct backlight_device *bl; 63 struct regmap *regmap; 64 struct gpio_desc *enable; 65 uint32_t iset; 66 uint8_t strings_mask; 67 }; 68 69 static const struct regmap_config max25014_regmap_config = { 70 .reg_bits = 8, 71 .val_bits = 8, 72 .max_register = MAX25014_DIAG, 73 }; 74 75 static int max25014_initial_power_state(struct max25014 *maxim) 76 { 77 uint32_t val; 78 int ret; 79 80 ret = regmap_read(maxim->regmap, MAX25014_ISET, &val); 81 if (ret) 82 return ret; 83 84 return val & MAX25014_ISET_ENA ? BACKLIGHT_POWER_ON : BACKLIGHT_POWER_OFF; 85 } 86 87 static int max25014_check_errors(struct max25014 *maxim) 88 { 89 uint32_t val; 90 uint8_t i; 91 int ret; 92 93 ret = regmap_read(maxim->regmap, MAX25014_OPEN, &val); 94 if (ret) 95 return ret; 96 if (val) { 97 dev_err(&maxim->client->dev, "Open led strings detected on:\n"); 98 for (i = 0; i < 4; i++) { 99 if (val & 1 << i) 100 dev_err(&maxim->client->dev, "string %d\n", i + 1); 101 } 102 return -EIO; 103 } 104 105 ret = regmap_read(maxim->regmap, MAX25014_SHORTGND, &val); 106 if (ret) 107 return ret; 108 if (val) { 109 dev_err(&maxim->client->dev, "Short to ground detected on:\n"); 110 for (i = 0; i < 4; i++) { 111 if (val & 1 << i) 112 dev_err(&maxim->client->dev, "string %d\n", i + 1); 113 } 114 return -EIO; 115 } 116 117 ret = regmap_read(maxim->regmap, MAX25014_SHORTED_LED, &val); 118 if (ret) 119 return ret; 120 if (val) { 121 dev_err(&maxim->client->dev, "Shorted led detected on:\n"); 122 for (i = 0; i < 4; i++) { 123 if (val & 1 << i) 124 dev_err(&maxim->client->dev, "string %d\n", i + 1); 125 } 126 return -EIO; 127 } 128 129 ret = regmap_read(maxim->regmap, MAX25014_DIAG, &val); 130 if (ret) 131 return ret; 132 /* 133 * The HW_RST bit always starts at 1 after power up. 134 * It is reset on first read, does not indicate an error. 135 */ 136 if (val && val != MAX25014_DIAG_HW_RST) { 137 if (val & MAX25014_DIAG_OT) 138 dev_err(&maxim->client->dev, 139 "Overtemperature shutdown\n"); 140 if (val & MAX25014_DIAG_OTW) 141 dev_err(&maxim->client->dev, 142 "Chip is getting too hot (>125C)\n"); 143 if (val & MAX25014_DIAG_BSTOV) 144 dev_err(&maxim->client->dev, 145 "Boost converter overvoltage\n"); 146 if (val & MAX25014_DIAG_BSTUV) 147 dev_err(&maxim->client->dev, 148 "Boost converter undervoltage\n"); 149 if (val & MAX25014_DIAG_IREFOOR) 150 dev_err(&maxim->client->dev, "IREF out of range\n"); 151 return -EIO; 152 } 153 return 0; 154 } 155 156 /* 157 * 1. disable unused strings 158 * 2. set dim mode 159 * 3. set setting register 160 * 4. enable the backlight 161 */ 162 static int max25014_configure(struct max25014 *maxim, int initial_state) 163 { 164 uint32_t val; 165 int ret; 166 167 ret = regmap_read(maxim->regmap, MAX25014_DISABLE, &val); 168 if (ret) 169 return ret; 170 171 /* 172 * Strings can only be disabled when MAX25014_ISET_ENA == 0, check if 173 * it needs to be changed at all to prevent the backlight flashing when 174 * it is configured correctly by the bootloader 175 */ 176 if (!((val & MAX25014_DISABLE_DIS_MASK) == maxim->strings_mask)) { 177 if (initial_state == BACKLIGHT_POWER_ON) { 178 ret = regmap_write(maxim->regmap, MAX25014_ISET, 0); 179 if (ret) 180 return ret; 181 } 182 ret = regmap_write(maxim->regmap, MAX25014_DISABLE, maxim->strings_mask); 183 if (ret) 184 return ret; 185 } 186 187 ret = regmap_write(maxim->regmap, MAX25014_IMODE, MAX25014_IMODE_HDIM); 188 if (ret) 189 return ret; 190 191 ret = regmap_read(maxim->regmap, MAX25014_SETTING, &val); 192 if (ret) 193 return ret; 194 195 ret = regmap_write(maxim->regmap, MAX25014_SETTING, 196 val & ~MAX25014_SETTING_FPWM); 197 if (ret) 198 return ret; 199 200 return regmap_write(maxim->regmap, MAX25014_ISET, 201 maxim->iset | MAX25014_ISET_ENA | 202 MAX25014_ISET_PSEN); 203 } 204 205 static int max25014_update_status(struct backlight_device *bl_dev) 206 { 207 struct max25014 *maxim = bl_get_data(bl_dev); 208 uint32_t reg; 209 int ret; 210 211 reg = TON_STEP * backlight_get_brightness(bl_dev); 212 213 /* 214 * 18 bit number lowest, 2 bits in first register, 215 * next lowest 8 in the L register, next 8 in the H register 216 * Seemingly setting the strength of only one string controls all of 217 * them, individual settings don't affect the outcome. 218 */ 219 ret = regmap_write(maxim->regmap, MAX25014_TON_1_4_LSB, reg & 0b00000011); 220 if (ret != 0) 221 return ret; 222 ret = regmap_write(maxim->regmap, MAX25014_TON1L, (reg >> 2) & 0b11111111); 223 if (ret != 0) 224 return ret; 225 return regmap_write(maxim->regmap, MAX25014_TON1H, (reg >> 10) & 0b11111111); 226 } 227 228 static const struct backlight_ops max25014_bl_ops = { 229 .options = BL_CORE_SUSPENDRESUME, 230 .update_status = max25014_update_status, 231 }; 232 233 static int max25014_parse_dt(struct max25014 *maxim, 234 uint32_t *initial_brightness) 235 { 236 struct device *dev = &maxim->client->dev; 237 struct device_node *node = dev->of_node; 238 uint32_t strings[4]; 239 int res, i; 240 241 res = of_property_count_u32_elems(node, "maxim,strings"); 242 if (res == 4) { 243 of_property_read_u32_array(node, "maxim,strings", strings, 4); 244 for (i = 0; i < 4; i++) { 245 if (strings[i] == 0) 246 maxim->strings_mask |= 1 << i; 247 } 248 } else { 249 maxim->strings_mask = 0; 250 } 251 252 *initial_brightness = 50U; 253 of_property_read_u32(node, "default-brightness", initial_brightness); 254 255 maxim->iset = MAX25014_ISET_DEFAULT_100; 256 of_property_read_u32(node, "maxim,iset", &maxim->iset); 257 258 if (maxim->iset > 15) 259 return dev_err_probe(dev, -EINVAL, 260 "Invalid iset, should be a value from 0-15, entered was %d\n", 261 maxim->iset); 262 263 if (*initial_brightness > 100) 264 return dev_err_probe(dev, -EINVAL, 265 "Invalid initial brightness, should be a value from 0-100, entered was %d\n", 266 *initial_brightness); 267 268 return 0; 269 } 270 271 static int max25014_probe(struct i2c_client *cl) 272 { 273 const struct i2c_device_id *id = i2c_client_get_device_id(cl); 274 struct backlight_properties props; 275 uint32_t initial_brightness = 50; 276 struct backlight_device *bl; 277 struct max25014 *maxim; 278 int ret; 279 280 maxim = devm_kzalloc(&cl->dev, sizeof(struct max25014), GFP_KERNEL); 281 if (!maxim) 282 return -ENOMEM; 283 284 maxim->client = cl; 285 286 ret = max25014_parse_dt(maxim, &initial_brightness); 287 if (ret) 288 return ret; 289 290 ret = devm_regulator_get_enable(&maxim->client->dev, "power"); 291 if (ret) 292 return dev_err_probe(&maxim->client->dev, ret, 293 "failed to get power-supply"); 294 295 maxim->enable = devm_gpiod_get_optional(&maxim->client->dev, "enable", 296 GPIOD_OUT_HIGH); 297 if (IS_ERR(maxim->enable)) 298 return dev_err_probe(&maxim->client->dev, PTR_ERR(maxim->enable), 299 "failed to get enable gpio\n"); 300 301 /* Datasheet Electrical Characteristics tSTARTUP 2ms */ 302 fsleep(2000); 303 304 maxim->regmap = devm_regmap_init_i2c(cl, &max25014_regmap_config); 305 if (IS_ERR(maxim->regmap)) 306 return dev_err_probe(&maxim->client->dev, PTR_ERR(maxim->regmap), 307 "failed to initialize the i2c regmap\n"); 308 309 i2c_set_clientdata(cl, maxim); 310 311 ret = max25014_check_errors(maxim); 312 if (ret) /* error is already reported in the above function */ 313 return ret; 314 315 ret = max25014_initial_power_state(maxim); 316 if (ret < 0) 317 return dev_err_probe(&maxim->client->dev, ret, "Could not get enabled state\n"); 318 319 memset(&props, 0, sizeof(struct backlight_properties)); 320 props.type = BACKLIGHT_PLATFORM; 321 props.max_brightness = MAX_BRIGHTNESS; 322 props.brightness = initial_brightness; 323 props.scale = BACKLIGHT_SCALE_LINEAR; 324 props.power = ret; 325 326 ret = max25014_configure(maxim, ret); 327 if (ret) 328 return dev_err_probe(&maxim->client->dev, ret, "device config error"); 329 330 bl = devm_backlight_device_register(&maxim->client->dev, id->name, 331 &maxim->client->dev, maxim, 332 &max25014_bl_ops, &props); 333 if (IS_ERR(bl)) 334 return dev_err_probe(&maxim->client->dev, PTR_ERR(bl), 335 "failed to register backlight\n"); 336 337 maxim->bl = bl; 338 339 backlight_update_status(maxim->bl); 340 341 return 0; 342 } 343 344 static void max25014_remove(struct i2c_client *cl) 345 { 346 struct max25014 *maxim = i2c_get_clientdata(cl); 347 348 backlight_device_set_brightness(maxim->bl, 0); 349 gpiod_set_value_cansleep(maxim->enable, 0); 350 } 351 352 static const struct of_device_id max25014_dt_ids[] = { 353 { .compatible = "maxim,max25014", }, 354 { } 355 }; 356 MODULE_DEVICE_TABLE(of, max25014_dt_ids); 357 358 static const struct i2c_device_id max25014_ids[] = { 359 { "max25014" }, 360 { } 361 }; 362 MODULE_DEVICE_TABLE(i2c, max25014_ids); 363 364 static struct i2c_driver max25014_driver = { 365 .driver = { 366 .name = KBUILD_MODNAME, 367 .of_match_table = of_match_ptr(max25014_dt_ids), 368 }, 369 .probe = max25014_probe, 370 .remove = max25014_remove, 371 .id_table = max25014_ids, 372 }; 373 module_i2c_driver(max25014_driver); 374 375 MODULE_DESCRIPTION("Maxim MAX25014 backlight driver"); 376 MODULE_AUTHOR("Maud Spierings <maudspierings@gocontroll.com>"); 377 MODULE_LICENSE("GPL"); 378