drivers/rtc/rtc-max6900.c

   1 /*
   2  * rtc class driver for the Maxim MAX6900 chip
   3  *
   4  * Author: Dale Farnsworth <dale@farnsworth.org>
   5  *
   6  * based on previously existing rtc class drivers
   7  *
   8  * 2007 (c) MontaVista, Software, Inc.  This file is licensed under
   9  * the terms of the GNU General Public License version 2.  This program
  10  * is licensed "as is" without any warranty of any kind, whether express
  11  * or implied.
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/i2c.h>
  16 #include <linux/bcd.h>
  17 #include <linux/rtc.h>
  18 #include <linux/delay.h>
  19
  20 #define DRV_NAME "max6900"
  21 #define DRV_VERSION "0.1"
  22
  23 /*
  24  * register indices
  25  */
  26 #define MAX6900_REG_SC                  0       /* seconds      00-59 */
  27 #define MAX6900_REG_MN                  1       /* minutes      00-59 */
  28 #define MAX6900_REG_HR                  2       /* hours        00-23 */
  29 #define MAX6900_REG_DT                  3       /* day of month 00-31 */
  30 #define MAX6900_REG_MO                  4       /* month        01-12 */
  31 #define MAX6900_REG_DW                  5       /* day of week   1-7  */
  32 #define MAX6900_REG_YR                  6       /* year         00-99 */
  33 #define MAX6900_REG_CT                  7       /* control */
  34                                                 /* register 8 is undocumented */
  35 #define MAX6900_REG_CENTURY             9       /* century */
  36 #define MAX6900_REG_LEN                 10
  37
  38 #define MAX6900_BURST_LEN               8       /* can burst r/w first 8 regs */
  39
  40 #define MAX6900_REG_CT_WP               (1 << 7)        /* Write Protect */
  41
  42
  43 /*
  44  * register read/write commands
  45  */
  46 #define MAX6900_REG_CONTROL_WRITE       0x8e
  47 #define MAX6900_REG_CENTURY_WRITE       0x92
  48 #define MAX6900_REG_CENTURY_READ        0x93
  49 #define MAX6900_REG_RESERVED_READ       0x96
  50 #define MAX6900_REG_BURST_WRITE         0xbe
  51 #define MAX6900_REG_BURST_READ          0xbf
  52
  53 #define MAX6900_IDLE_TIME_AFTER_WRITE   3       /* specification says 2.5 mS */
  54
  55 #define MAX6900_I2C_ADDR                0xa0
  56
  57 static const unsigned short normal_i2c[] = {
  58         MAX6900_I2C_ADDR >> 1,
  59         I2C_CLIENT_END
  60 };
  61
  62 I2C_CLIENT_INSMOD;                      /* defines addr_data */
  63
  64 static int max6900_probe(struct i2c_adapter *adapter, int addr, int kind);
  65
  66 static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
  67 {
  68         u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };
  69         u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };
  70         struct i2c_msg msgs[4] = {
  71                 {
  72                         .addr   = client->addr,
  73                         .flags  = 0, /* write */
  74                         .len    = sizeof(reg_burst_read),
  75                         .buf    = reg_burst_read
  76                 },
  77                 {
  78                         .addr   = client->addr,
  79                         .flags  = I2C_M_RD,
  80                         .len    = MAX6900_BURST_LEN,
  81                         .buf    = buf
  82                 },
  83                 {
  84                         .addr   = client->addr,
  85                         .flags  = 0, /* write */
  86                         .len    = sizeof(reg_century_read),
  87                         .buf    = reg_century_read
  88                 },
  89                 {
  90                         .addr   = client->addr,
  91                         .flags  = I2C_M_RD,
  92                         .len    = sizeof(buf[MAX6900_REG_CENTURY]),
  93                         .buf    = &buf[MAX6900_REG_CENTURY]
  94                 }
  95         };
  96         int rc;
  97
  98         rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
  99         if (rc != ARRAY_SIZE(msgs)) {
 100                 dev_err(&client->dev, "%s: register read failed\n",
 101                         __func__);
 102                 return -EIO;
 103         }
 104         return 0;
 105 }
 106
 107 static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
 108 {
 109         u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE };
 110         struct i2c_msg century_msgs[1] = {
 111                 {
 112                         .addr   = client->addr,
 113                         .flags  = 0, /* write */
 114                         .len    = sizeof(i2c_century_buf),
 115                         .buf    = i2c_century_buf
 116                 }
 117         };
 118         u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE };
 119         struct i2c_msg burst_msgs[1] = {
 120                 {
 121                         .addr   = client->addr,
 122                         .flags  = 0, /* write */
 123                         .len    = sizeof(i2c_burst_buf),
 124                         .buf    = i2c_burst_buf
 125                 }
 126         };
 127         int rc;
 128
 129         /*
 130          * We have to make separate calls to i2c_transfer because of
 131          * the need to delay after each write to the chip.  Also,
 132          * we write the century byte first, since we set the write-protect
 133          * bit as part of the burst write.
 134          */
 135         i2c_century_buf[1] = buf[MAX6900_REG_CENTURY];
 136         rc = i2c_transfer(client->adapter, century_msgs,
 137                           ARRAY_SIZE(century_msgs));
 138         if (rc != ARRAY_SIZE(century_msgs))
 139                 goto write_failed;
 140         msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
 141
 142         memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN);
 143
 144         rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs));
 145         if (rc != ARRAY_SIZE(burst_msgs))
 146                 goto write_failed;
 147         msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
 148
 149         return 0;
 150
 151 write_failed:
 152         dev_err(&client->dev, "%s: register write failed\n",
 153                 __func__);
 154         return -EIO;
 155 }
 156
 157 static int max6900_i2c_validate_client(struct i2c_client *client)
 158 {
 159         u8 regs[MAX6900_REG_LEN];
 160         u8 zero_mask[] = {
 161                 0x80,   /* seconds */
 162                 0x80,   /* minutes */
 163                 0x40,   /* hours */
 164                 0xc0,   /* day of month */
 165                 0xe0,   /* month */
 166                 0xf8,   /* day of week */
 167                 0x00,   /* year */
 168                 0x7f,   /* control */
 169         };
 170         int i;
 171         int rc;
 172         int reserved;
 173
 174         reserved = i2c_smbus_read_byte_data(client, MAX6900_REG_RESERVED_READ);
 175         if (reserved != 0x07)
 176                 return -ENODEV;
 177
 178         rc = max6900_i2c_read_regs(client, regs);
 179         if (rc < 0)
 180                 return rc;
 181
 182         for (i = 0; i < ARRAY_SIZE(zero_mask); ++i) {
 183                 if (regs[i] & zero_mask[i])
 184                         return -ENODEV;
 185         }
 186
 187         return 0;
 188 }
 189
 190 static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
 191 {
 192         int rc;
 193         u8 regs[MAX6900_REG_LEN];
 194
 195         rc = max6900_i2c_read_regs(client, regs);
 196         if (rc < 0)
 197                 return rc;
 198
 199         tm->tm_sec = BCD2BIN(regs[MAX6900_REG_SC]);
 200         tm->tm_min = BCD2BIN(regs[MAX6900_REG_MN]);
 201         tm->tm_hour = BCD2BIN(regs[MAX6900_REG_HR] & 0x3f);
 202         tm->tm_mday = BCD2BIN(regs[MAX6900_REG_DT]);
 203         tm->tm_mon = BCD2BIN(regs[MAX6900_REG_MO]) - 1;
 204         tm->tm_year = BCD2BIN(regs[MAX6900_REG_YR]) +
 205                       BCD2BIN(regs[MAX6900_REG_CENTURY]) * 100 - 1900;
 206         tm->tm_wday = BCD2BIN(regs[MAX6900_REG_DW]);
 207
 208         return 0;
 209 }
 210
 211 static int max6900_i2c_clear_write_protect(struct i2c_client *client)
 212 {
 213         int rc;
 214         rc = i2c_smbus_write_byte_data (client, MAX6900_REG_CONTROL_WRITE, 0);
 215         if (rc < 0) {
 216                 dev_err(&client->dev, "%s: control register write failed\n",
 217                         __func__);
 218                 return -EIO;
 219         }
 220         return 0;
 221 }
 222
 223 static int max6900_i2c_set_time(struct i2c_client *client,
 224                                 struct rtc_time const *tm)
 225 {
 226         u8 regs[MAX6900_REG_LEN];
 227         int rc;
 228
 229         rc = max6900_i2c_clear_write_protect(client);
 230         if (rc < 0)
 231                 return rc;
 232
 233         regs[MAX6900_REG_SC] = BIN2BCD(tm->tm_sec);
 234         regs[MAX6900_REG_MN] = BIN2BCD(tm->tm_min);
 235         regs[MAX6900_REG_HR] = BIN2BCD(tm->tm_hour);
 236         regs[MAX6900_REG_DT] = BIN2BCD(tm->tm_mday);
 237         regs[MAX6900_REG_MO] = BIN2BCD(tm->tm_mon + 1);
 238         regs[MAX6900_REG_DW] = BIN2BCD(tm->tm_wday);
 239         regs[MAX6900_REG_YR] = BIN2BCD(tm->tm_year % 100);
 240         regs[MAX6900_REG_CENTURY] = BIN2BCD((tm->tm_year + 1900) / 100);
 241         /* set write protect */
 242         regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;
 243
 244         rc = max6900_i2c_write_regs(client, regs);
 245         if (rc < 0)
 246                 return rc;
 247
 248         return 0;
 249 }
 250
 251 static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm)
 252 {
 253         return max6900_i2c_read_time(to_i2c_client(dev), tm);
 254 }
 255
 256 static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)
 257 {
 258         return max6900_i2c_set_time(to_i2c_client(dev), tm);
 259 }
 260
 261 static int max6900_attach_adapter(struct i2c_adapter *adapter)
 262 {
 263         return i2c_probe(adapter, &addr_data, max6900_probe);
 264 }
 265
 266 static int max6900_detach_client(struct i2c_client *client)
 267 {
 268         struct rtc_device *const rtc = i2c_get_clientdata(client);
 269
 270         if (rtc)
 271                 rtc_device_unregister(rtc);
 272
 273         return i2c_detach_client(client);
 274 }
 275
 276 static struct i2c_driver max6900_driver = {
 277         .driver         = {
 278                 .name   = DRV_NAME,
 279         },
 280         .id             = I2C_DRIVERID_MAX6900,
 281         .attach_adapter = max6900_attach_adapter,
 282         .detach_client  = max6900_detach_client,
 283 };
 284
 285 static const struct rtc_class_ops max6900_rtc_ops = {
 286         .read_time      = max6900_rtc_read_time,
 287         .set_time       = max6900_rtc_set_time,
 288 };
 289
 290 static int max6900_probe(struct i2c_adapter *adapter, int addr, int kind)
 291 {
 292         int rc = 0;
 293         struct i2c_client *client = NULL;
 294         struct rtc_device *rtc = NULL;
 295
 296         if (!i2c_check_functionality(adapter, I2C_FUNC_I2C)) {
 297                 rc = -ENODEV;
 298                 goto failout;
 299         }
 300
 301         client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
 302         if (client == NULL) {
 303                 rc = -ENOMEM;
 304                 goto failout;
 305         }
 306
 307         client->addr = addr;
 308         client->adapter = adapter;
 309         client->driver = &max6900_driver;
 310         strlcpy(client->name, DRV_NAME, I2C_NAME_SIZE);
 311
 312         if (kind < 0) {
 313                 rc = max6900_i2c_validate_client(client);
 314                 if (rc < 0)
 315                         goto failout;
 316         }
 317
 318         rc = i2c_attach_client(client);
 319         if (rc < 0)
 320                 goto failout;
 321
 322         dev_info(&client->dev,
 323                  "chip found, driver version " DRV_VERSION "\n");
 324
 325         rtc = rtc_device_register(max6900_driver.driver.name,
 326                                   &client->dev,
 327                                   &max6900_rtc_ops, THIS_MODULE);
 328         if (IS_ERR(rtc)) {
 329                 rc = PTR_ERR(rtc);
 330                 goto failout_detach;
 331         }
 332
 333         i2c_set_clientdata(client, rtc);
 334
 335         return 0;
 336
 337 failout_detach:
 338         i2c_detach_client(client);
 339 failout:
 340         kfree(client);
 341         return rc;
 342 }
 343
 344 static int __init max6900_init(void)
 345 {
 346         return i2c_add_driver(&max6900_driver);
 347 }
 348
 349 static void __exit max6900_exit(void)
 350 {
 351         i2c_del_driver(&max6900_driver);
 352 }
 353
 354 MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
 355 MODULE_LICENSE("GPL");
 356 MODULE_VERSION(DRV_VERSION);
 357
 358 module_init(max6900_init);
 359 module_exit(max6900_exit);