1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2012 Avionic Design GmbH 4 */ 5 6 #include <linux/bcd.h> 7 #include <linux/i2c.h> 8 #include <linux/module.h> 9 #include <linux/rtc.h> 10 #include <linux/of.h> 11 12 #define DRIVER_NAME "rtc-pcf8523" 13 14 #define REG_CONTROL1 0x00 15 #define REG_CONTROL1_CAP_SEL (1 << 7) 16 #define REG_CONTROL1_STOP (1 << 5) 17 18 #define REG_CONTROL3 0x02 19 #define REG_CONTROL3_PM_BLD (1 << 7) /* battery low detection disabled */ 20 #define REG_CONTROL3_PM_VDD (1 << 6) /* switch-over disabled */ 21 #define REG_CONTROL3_PM_DSM (1 << 5) /* direct switching mode */ 22 #define REG_CONTROL3_PM_MASK 0xe0 23 #define REG_CONTROL3_BLF (1 << 2) /* battery low bit, read-only */ 24 25 #define REG_SECONDS 0x03 26 #define REG_SECONDS_OS (1 << 7) 27 28 #define REG_MINUTES 0x04 29 #define REG_HOURS 0x05 30 #define REG_DAYS 0x06 31 #define REG_WEEKDAYS 0x07 32 #define REG_MONTHS 0x08 33 #define REG_YEARS 0x09 34 35 #define REG_OFFSET 0x0e 36 #define REG_OFFSET_MODE BIT(7) 37 38 struct pcf8523 { 39 struct rtc_device *rtc; 40 }; 41 42 static int pcf8523_read(struct i2c_client *client, u8 reg, u8 *valuep) 43 { 44 struct i2c_msg msgs[2]; 45 u8 value = 0; 46 int err; 47 48 msgs[0].addr = client->addr; 49 msgs[0].flags = 0; 50 msgs[0].len = sizeof(reg); 51 msgs[0].buf = ® 52 53 msgs[1].addr = client->addr; 54 msgs[1].flags = I2C_M_RD; 55 msgs[1].len = sizeof(value); 56 msgs[1].buf = &value; 57 58 err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs)); 59 if (err < 0) 60 return err; 61 62 *valuep = value; 63 64 return 0; 65 } 66 67 static int pcf8523_write(struct i2c_client *client, u8 reg, u8 value) 68 { 69 u8 buffer[2] = { reg, value }; 70 struct i2c_msg msg; 71 int err; 72 73 msg.addr = client->addr; 74 msg.flags = 0; 75 msg.len = sizeof(buffer); 76 msg.buf = buffer; 77 78 err = i2c_transfer(client->adapter, &msg, 1); 79 if (err < 0) 80 return err; 81 82 return 0; 83 } 84 85 static int pcf8523_voltage_low(struct i2c_client *client) 86 { 87 u8 value; 88 int err; 89 90 err = pcf8523_read(client, REG_CONTROL3, &value); 91 if (err < 0) 92 return err; 93 94 return !!(value & REG_CONTROL3_BLF); 95 } 96 97 static int pcf8523_load_capacitance(struct i2c_client *client) 98 { 99 u32 load; 100 u8 value; 101 int err; 102 103 err = pcf8523_read(client, REG_CONTROL1, &value); 104 if (err < 0) 105 return err; 106 107 load = 12500; 108 of_property_read_u32(client->dev.of_node, "quartz-load-femtofarads", 109 &load); 110 111 switch (load) { 112 default: 113 dev_warn(&client->dev, "Unknown quartz-load-femtofarads value: %d. Assuming 12500", 114 load); 115 /* fall through */ 116 case 12500: 117 value |= REG_CONTROL1_CAP_SEL; 118 break; 119 case 7000: 120 value &= ~REG_CONTROL1_CAP_SEL; 121 break; 122 } 123 124 err = pcf8523_write(client, REG_CONTROL1, value); 125 126 return err; 127 } 128 129 static int pcf8523_set_pm(struct i2c_client *client, u8 pm) 130 { 131 u8 value; 132 int err; 133 134 err = pcf8523_read(client, REG_CONTROL3, &value); 135 if (err < 0) 136 return err; 137 138 value = (value & ~REG_CONTROL3_PM_MASK) | pm; 139 140 err = pcf8523_write(client, REG_CONTROL3, value); 141 if (err < 0) 142 return err; 143 144 return 0; 145 } 146 147 static int pcf8523_stop_rtc(struct i2c_client *client) 148 { 149 u8 value; 150 int err; 151 152 err = pcf8523_read(client, REG_CONTROL1, &value); 153 if (err < 0) 154 return err; 155 156 value |= REG_CONTROL1_STOP; 157 158 err = pcf8523_write(client, REG_CONTROL1, value); 159 if (err < 0) 160 return err; 161 162 return 0; 163 } 164 165 static int pcf8523_start_rtc(struct i2c_client *client) 166 { 167 u8 value; 168 int err; 169 170 err = pcf8523_read(client, REG_CONTROL1, &value); 171 if (err < 0) 172 return err; 173 174 value &= ~REG_CONTROL1_STOP; 175 176 err = pcf8523_write(client, REG_CONTROL1, value); 177 if (err < 0) 178 return err; 179 180 return 0; 181 } 182 183 static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm) 184 { 185 struct i2c_client *client = to_i2c_client(dev); 186 u8 start = REG_SECONDS, regs[7]; 187 struct i2c_msg msgs[2]; 188 int err; 189 190 err = pcf8523_voltage_low(client); 191 if (err < 0) { 192 return err; 193 } else if (err > 0) { 194 dev_err(dev, "low voltage detected, time is unreliable\n"); 195 return -EINVAL; 196 } 197 198 msgs[0].addr = client->addr; 199 msgs[0].flags = 0; 200 msgs[0].len = 1; 201 msgs[0].buf = &start; 202 203 msgs[1].addr = client->addr; 204 msgs[1].flags = I2C_M_RD; 205 msgs[1].len = sizeof(regs); 206 msgs[1].buf = regs; 207 208 err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs)); 209 if (err < 0) 210 return err; 211 212 if (regs[0] & REG_SECONDS_OS) 213 return -EINVAL; 214 215 tm->tm_sec = bcd2bin(regs[0] & 0x7f); 216 tm->tm_min = bcd2bin(regs[1] & 0x7f); 217 tm->tm_hour = bcd2bin(regs[2] & 0x3f); 218 tm->tm_mday = bcd2bin(regs[3] & 0x3f); 219 tm->tm_wday = regs[4] & 0x7; 220 tm->tm_mon = bcd2bin(regs[5] & 0x1f) - 1; 221 tm->tm_year = bcd2bin(regs[6]) + 100; 222 223 return 0; 224 } 225 226 static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm) 227 { 228 struct i2c_client *client = to_i2c_client(dev); 229 struct i2c_msg msg; 230 u8 regs[8]; 231 int err; 232 233 /* 234 * The hardware can only store values between 0 and 99 in it's YEAR 235 * register (with 99 overflowing to 0 on increment). 236 * After 2100-02-28 we could start interpreting the year to be in the 237 * interval [2100, 2199], but there is no path to switch in a smooth way 238 * because the chip handles YEAR=0x00 (and the out-of-spec 239 * YEAR=0xa0) as a leap year, but 2100 isn't. 240 */ 241 if (tm->tm_year < 100 || tm->tm_year >= 200) 242 return -EINVAL; 243 244 err = pcf8523_stop_rtc(client); 245 if (err < 0) 246 return err; 247 248 regs[0] = REG_SECONDS; 249 /* This will purposely overwrite REG_SECONDS_OS */ 250 regs[1] = bin2bcd(tm->tm_sec); 251 regs[2] = bin2bcd(tm->tm_min); 252 regs[3] = bin2bcd(tm->tm_hour); 253 regs[4] = bin2bcd(tm->tm_mday); 254 regs[5] = tm->tm_wday; 255 regs[6] = bin2bcd(tm->tm_mon + 1); 256 regs[7] = bin2bcd(tm->tm_year - 100); 257 258 msg.addr = client->addr; 259 msg.flags = 0; 260 msg.len = sizeof(regs); 261 msg.buf = regs; 262 263 err = i2c_transfer(client->adapter, &msg, 1); 264 if (err < 0) { 265 /* 266 * If the time cannot be set, restart the RTC anyway. Note 267 * that errors are ignored if the RTC cannot be started so 268 * that we have a chance to propagate the original error. 269 */ 270 pcf8523_start_rtc(client); 271 return err; 272 } 273 274 return pcf8523_start_rtc(client); 275 } 276 277 #ifdef CONFIG_RTC_INTF_DEV 278 static int pcf8523_rtc_ioctl(struct device *dev, unsigned int cmd, 279 unsigned long arg) 280 { 281 struct i2c_client *client = to_i2c_client(dev); 282 int ret; 283 284 switch (cmd) { 285 case RTC_VL_READ: 286 ret = pcf8523_voltage_low(client); 287 if (ret < 0) 288 return ret; 289 290 if (copy_to_user((void __user *)arg, &ret, sizeof(int))) 291 return -EFAULT; 292 293 return 0; 294 default: 295 return -ENOIOCTLCMD; 296 } 297 } 298 #else 299 #define pcf8523_rtc_ioctl NULL 300 #endif 301 302 static int pcf8523_rtc_read_offset(struct device *dev, long *offset) 303 { 304 struct i2c_client *client = to_i2c_client(dev); 305 int err; 306 u8 value; 307 s8 val; 308 309 err = pcf8523_read(client, REG_OFFSET, &value); 310 if (err < 0) 311 return err; 312 313 /* sign extend the 7-bit offset value */ 314 val = value << 1; 315 *offset = (value & REG_OFFSET_MODE ? 4069 : 4340) * (val >> 1); 316 317 return 0; 318 } 319 320 static int pcf8523_rtc_set_offset(struct device *dev, long offset) 321 { 322 struct i2c_client *client = to_i2c_client(dev); 323 long reg_m0, reg_m1; 324 u8 value; 325 326 reg_m0 = clamp(DIV_ROUND_CLOSEST(offset, 4340), -64L, 63L); 327 reg_m1 = clamp(DIV_ROUND_CLOSEST(offset, 4069), -64L, 63L); 328 329 if (abs(reg_m0 * 4340 - offset) < abs(reg_m1 * 4069 - offset)) 330 value = reg_m0 & 0x7f; 331 else 332 value = (reg_m1 & 0x7f) | REG_OFFSET_MODE; 333 334 return pcf8523_write(client, REG_OFFSET, value); 335 } 336 337 static const struct rtc_class_ops pcf8523_rtc_ops = { 338 .read_time = pcf8523_rtc_read_time, 339 .set_time = pcf8523_rtc_set_time, 340 .ioctl = pcf8523_rtc_ioctl, 341 .read_offset = pcf8523_rtc_read_offset, 342 .set_offset = pcf8523_rtc_set_offset, 343 }; 344 345 static int pcf8523_probe(struct i2c_client *client, 346 const struct i2c_device_id *id) 347 { 348 struct pcf8523 *pcf; 349 int err; 350 351 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) 352 return -ENODEV; 353 354 pcf = devm_kzalloc(&client->dev, sizeof(*pcf), GFP_KERNEL); 355 if (!pcf) 356 return -ENOMEM; 357 358 err = pcf8523_load_capacitance(client); 359 if (err < 0) 360 dev_warn(&client->dev, "failed to set xtal load capacitance: %d", 361 err); 362 363 err = pcf8523_set_pm(client, 0); 364 if (err < 0) 365 return err; 366 367 pcf->rtc = devm_rtc_device_register(&client->dev, DRIVER_NAME, 368 &pcf8523_rtc_ops, THIS_MODULE); 369 if (IS_ERR(pcf->rtc)) 370 return PTR_ERR(pcf->rtc); 371 372 i2c_set_clientdata(client, pcf); 373 374 return 0; 375 } 376 377 static const struct i2c_device_id pcf8523_id[] = { 378 { "pcf8523", 0 }, 379 { } 380 }; 381 MODULE_DEVICE_TABLE(i2c, pcf8523_id); 382 383 #ifdef CONFIG_OF 384 static const struct of_device_id pcf8523_of_match[] = { 385 { .compatible = "nxp,pcf8523" }, 386 { .compatible = "microcrystal,rv8523" }, 387 { } 388 }; 389 MODULE_DEVICE_TABLE(of, pcf8523_of_match); 390 #endif 391 392 static struct i2c_driver pcf8523_driver = { 393 .driver = { 394 .name = DRIVER_NAME, 395 .of_match_table = of_match_ptr(pcf8523_of_match), 396 }, 397 .probe = pcf8523_probe, 398 .id_table = pcf8523_id, 399 }; 400 module_i2c_driver(pcf8523_driver); 401 402 MODULE_AUTHOR("Thierry Reding <thierry.reding@avionic-design.de>"); 403 MODULE_DESCRIPTION("NXP PCF8523 RTC driver"); 404 MODULE_LICENSE("GPL v2"); 405