drivers/rtc/rtc-pcf8523.c

   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 BIT(7)
  16 #define REG_CONTROL1_STOP    BIT(5)
  17
  18 #define REG_CONTROL3 0x02
  19 #define REG_CONTROL3_PM_BLD BIT(7) /* battery low detection disabled */
  20 #define REG_CONTROL3_PM_VDD BIT(6) /* switch-over disabled */
  21 #define REG_CONTROL3_PM_DSM BIT(5) /* direct switching mode */
  22 #define REG_CONTROL3_PM_MASK 0xe0
  23 #define REG_CONTROL3_BLF BIT(2) /* battery low bit, read-only */
  24
  25 #define REG_SECONDS  0x03
  26 #define REG_SECONDS_OS BIT(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 static int pcf8523_read(struct i2c_client *client, u8 reg, u8 *valuep)
  39 {
  40         struct i2c_msg msgs[2];
  41         u8 value = 0;
  42         int err;
  43
  44         msgs[0].addr = client->addr;
  45         msgs[0].flags = 0;
  46         msgs[0].len = sizeof(reg);
  47         msgs[0].buf = &reg;
  48
  49         msgs[1].addr = client->addr;
  50         msgs[1].flags = I2C_M_RD;
  51         msgs[1].len = sizeof(value);
  52         msgs[1].buf = &value;
  53
  54         err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
  55         if (err < 0)
  56                 return err;
  57
  58         *valuep = value;
  59
  60         return 0;
  61 }
  62
  63 static int pcf8523_write(struct i2c_client *client, u8 reg, u8 value)
  64 {
  65         u8 buffer[2] = { reg, value };
  66         struct i2c_msg msg;
  67         int err;
  68
  69         msg.addr = client->addr;
  70         msg.flags = 0;
  71         msg.len = sizeof(buffer);
  72         msg.buf = buffer;
  73
  74         err = i2c_transfer(client->adapter, &msg, 1);
  75         if (err < 0)
  76                 return err;
  77
  78         return 0;
  79 }
  80
  81 static int pcf8523_voltage_low(struct i2c_client *client)
  82 {
  83         u8 value;
  84         int err;
  85
  86         err = pcf8523_read(client, REG_CONTROL3, &value);
  87         if (err < 0)
  88                 return err;
  89
  90         return !!(value & REG_CONTROL3_BLF);
  91 }
  92
  93 static int pcf8523_load_capacitance(struct i2c_client *client)
  94 {
  95         u32 load;
  96         u8 value;
  97         int err;
  98
  99         err = pcf8523_read(client, REG_CONTROL1, &value);
 100         if (err < 0)
 101                 return err;
 102
 103         load = 12500;
 104         of_property_read_u32(client->dev.of_node, "quartz-load-femtofarads",
 105                              &load);
 106
 107         switch (load) {
 108         default:
 109                 dev_warn(&client->dev, "Unknown quartz-load-femtofarads value: %d. Assuming 12500",
 110                          load);
 111                 fallthrough;
 112         case 12500:
 113                 value |= REG_CONTROL1_CAP_SEL;
 114                 break;
 115         case 7000:
 116                 value &= ~REG_CONTROL1_CAP_SEL;
 117                 break;
 118         }
 119
 120         err = pcf8523_write(client, REG_CONTROL1, value);
 121
 122         return err;
 123 }
 124
 125 static int pcf8523_set_pm(struct i2c_client *client, u8 pm)
 126 {
 127         u8 value;
 128         int err;
 129
 130         err = pcf8523_read(client, REG_CONTROL3, &value);
 131         if (err < 0)
 132                 return err;
 133
 134         value = (value & ~REG_CONTROL3_PM_MASK) | pm;
 135
 136         err = pcf8523_write(client, REG_CONTROL3, value);
 137         if (err < 0)
 138                 return err;
 139
 140         return 0;
 141 }
 142
 143 static int pcf8523_stop_rtc(struct i2c_client *client)
 144 {
 145         u8 value;
 146         int err;
 147
 148         err = pcf8523_read(client, REG_CONTROL1, &value);
 149         if (err < 0)
 150                 return err;
 151
 152         value |= REG_CONTROL1_STOP;
 153
 154         err = pcf8523_write(client, REG_CONTROL1, value);
 155         if (err < 0)
 156                 return err;
 157
 158         return 0;
 159 }
 160
 161 static int pcf8523_start_rtc(struct i2c_client *client)
 162 {
 163         u8 value;
 164         int err;
 165
 166         err = pcf8523_read(client, REG_CONTROL1, &value);
 167         if (err < 0)
 168                 return err;
 169
 170         value &= ~REG_CONTROL1_STOP;
 171
 172         err = pcf8523_write(client, REG_CONTROL1, value);
 173         if (err < 0)
 174                 return err;
 175
 176         return 0;
 177 }
 178
 179 static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm)
 180 {
 181         struct i2c_client *client = to_i2c_client(dev);
 182         u8 start = REG_SECONDS, regs[7];
 183         struct i2c_msg msgs[2];
 184         int err;
 185
 186         err = pcf8523_voltage_low(client);
 187         if (err < 0) {
 188                 return err;
 189         } else if (err > 0) {
 190                 dev_err(dev, "low voltage detected, time is unreliable\n");
 191                 return -EINVAL;
 192         }
 193
 194         msgs[0].addr = client->addr;
 195         msgs[0].flags = 0;
 196         msgs[0].len = 1;
 197         msgs[0].buf = &start;
 198
 199         msgs[1].addr = client->addr;
 200         msgs[1].flags = I2C_M_RD;
 201         msgs[1].len = sizeof(regs);
 202         msgs[1].buf = regs;
 203
 204         err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
 205         if (err < 0)
 206                 return err;
 207
 208         if (regs[0] & REG_SECONDS_OS)
 209                 return -EINVAL;
 210
 211         tm->tm_sec = bcd2bin(regs[0] & 0x7f);
 212         tm->tm_min = bcd2bin(regs[1] & 0x7f);
 213         tm->tm_hour = bcd2bin(regs[2] & 0x3f);
 214         tm->tm_mday = bcd2bin(regs[3] & 0x3f);
 215         tm->tm_wday = regs[4] & 0x7;
 216         tm->tm_mon = bcd2bin(regs[5] & 0x1f) - 1;
 217         tm->tm_year = bcd2bin(regs[6]) + 100;
 218
 219         return 0;
 220 }
 221
 222 static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm)
 223 {
 224         struct i2c_client *client = to_i2c_client(dev);
 225         struct i2c_msg msg;
 226         u8 regs[8];
 227         int err;
 228
 229         err = pcf8523_stop_rtc(client);
 230         if (err < 0)
 231                 return err;
 232
 233         regs[0] = REG_SECONDS;
 234         /* This will purposely overwrite REG_SECONDS_OS */
 235         regs[1] = bin2bcd(tm->tm_sec);
 236         regs[2] = bin2bcd(tm->tm_min);
 237         regs[3] = bin2bcd(tm->tm_hour);
 238         regs[4] = bin2bcd(tm->tm_mday);
 239         regs[5] = tm->tm_wday;
 240         regs[6] = bin2bcd(tm->tm_mon + 1);
 241         regs[7] = bin2bcd(tm->tm_year - 100);
 242
 243         msg.addr = client->addr;
 244         msg.flags = 0;
 245         msg.len = sizeof(regs);
 246         msg.buf = regs;
 247
 248         err = i2c_transfer(client->adapter, &msg, 1);
 249         if (err < 0) {
 250                 /*
 251                  * If the time cannot be set, restart the RTC anyway. Note
 252                  * that errors are ignored if the RTC cannot be started so
 253                  * that we have a chance to propagate the original error.
 254                  */
 255                 pcf8523_start_rtc(client);
 256                 return err;
 257         }
 258
 259         return pcf8523_start_rtc(client);
 260 }
 261
 262 #ifdef CONFIG_RTC_INTF_DEV
 263 static int pcf8523_rtc_ioctl(struct device *dev, unsigned int cmd,
 264                              unsigned long arg)
 265 {
 266         struct i2c_client *client = to_i2c_client(dev);
 267         int ret;
 268
 269         switch (cmd) {
 270         case RTC_VL_READ:
 271                 ret = pcf8523_voltage_low(client);
 272                 if (ret < 0)
 273                         return ret;
 274                 if (ret)
 275                         ret = RTC_VL_BACKUP_LOW;
 276
 277                 return put_user(ret, (unsigned int __user *)arg);
 278
 279         default:
 280                 return -ENOIOCTLCMD;
 281         }
 282 }
 283 #else
 284 #define pcf8523_rtc_ioctl NULL
 285 #endif
 286
 287 static int pcf8523_rtc_read_offset(struct device *dev, long *offset)
 288 {
 289         struct i2c_client *client = to_i2c_client(dev);
 290         int err;
 291         u8 value;
 292         s8 val;
 293
 294         err = pcf8523_read(client, REG_OFFSET, &value);
 295         if (err < 0)
 296                 return err;
 297
 298         /* sign extend the 7-bit offset value */
 299         val = value << 1;
 300         *offset = (value & REG_OFFSET_MODE ? 4069 : 4340) * (val >> 1);
 301
 302         return 0;
 303 }
 304
 305 static int pcf8523_rtc_set_offset(struct device *dev, long offset)
 306 {
 307         struct i2c_client *client = to_i2c_client(dev);
 308         long reg_m0, reg_m1;
 309         u8 value;
 310
 311         reg_m0 = clamp(DIV_ROUND_CLOSEST(offset, 4340), -64L, 63L);
 312         reg_m1 = clamp(DIV_ROUND_CLOSEST(offset, 4069), -64L, 63L);
 313
 314         if (abs(reg_m0 * 4340 - offset) < abs(reg_m1 * 4069 - offset))
 315                 value = reg_m0 & 0x7f;
 316         else
 317                 value = (reg_m1 & 0x7f) | REG_OFFSET_MODE;
 318
 319         return pcf8523_write(client, REG_OFFSET, value);
 320 }
 321
 322 static const struct rtc_class_ops pcf8523_rtc_ops = {
 323         .read_time = pcf8523_rtc_read_time,
 324         .set_time = pcf8523_rtc_set_time,
 325         .ioctl = pcf8523_rtc_ioctl,
 326         .read_offset = pcf8523_rtc_read_offset,
 327         .set_offset = pcf8523_rtc_set_offset,
 328 };
 329
 330 static int pcf8523_probe(struct i2c_client *client,
 331                          const struct i2c_device_id *id)
 332 {
 333         struct rtc_device *rtc;
 334         int err;
 335
 336         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 337                 return -ENODEV;
 338
 339         err = pcf8523_load_capacitance(client);
 340         if (err < 0)
 341                 dev_warn(&client->dev, "failed to set xtal load capacitance: %d",
 342                          err);
 343
 344         err = pcf8523_set_pm(client, 0);
 345         if (err < 0)
 346                 return err;
 347
 348         rtc = devm_rtc_allocate_device(&client->dev);
 349         if (IS_ERR(rtc))
 350                 return PTR_ERR(rtc);
 351
 352         rtc->ops = &pcf8523_rtc_ops;
 353         rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
 354         rtc->range_max = RTC_TIMESTAMP_END_2099;
 355
 356         return devm_rtc_register_device(rtc);
 357 }
 358
 359 static const struct i2c_device_id pcf8523_id[] = {
 360         { "pcf8523", 0 },
 361         { }
 362 };
 363 MODULE_DEVICE_TABLE(i2c, pcf8523_id);
 364
 365 #ifdef CONFIG_OF
 366 static const struct of_device_id pcf8523_of_match[] = {
 367         { .compatible = "nxp,pcf8523" },
 368         { .compatible = "microcrystal,rv8523" },
 369         { }
 370 };
 371 MODULE_DEVICE_TABLE(of, pcf8523_of_match);
 372 #endif
 373
 374 static struct i2c_driver pcf8523_driver = {
 375         .driver = {
 376                 .name = DRIVER_NAME,
 377                 .of_match_table = of_match_ptr(pcf8523_of_match),
 378         },
 379         .probe = pcf8523_probe,
 380         .id_table = pcf8523_id,
 381 };
 382 module_i2c_driver(pcf8523_driver);
 383
 384 MODULE_AUTHOR("Thierry Reding <thierry.reding@avionic-design.de>");
 385 MODULE_DESCRIPTION("NXP PCF8523 RTC driver");
 386 MODULE_LICENSE("GPL v2");