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   1 /*
   2  * drivers/i2c/chips/ds1374.c
   3  *
   4  * I2C client/driver for the Maxim/Dallas DS1374 Real-Time Clock
   5  *
   6  * Author: Randy Vinson <rvinson@mvista.com>
   7  *
   8  * Based on the m41t00.c by Mark Greer <mgreer@mvista.com>
   9  *
  10  * 2005 (c) MontaVista Software, Inc. This file is licensed under
  11  * the terms of the GNU General Public License version 2. This program
  12  * is licensed "as is" without any warranty of any kind, whether express
  13  * or implied.
  14  */
  15 /*
  16  * This i2c client/driver wedges between the drivers/char/genrtc.c RTC
  17  * interface and the SMBus interface of the i2c subsystem.
  18  * It would be more efficient to use i2c msgs/i2c_transfer directly but, as
  19  * recommened in .../Documentation/i2c/writing-clients section
  20  * "Sending and receiving", using SMBus level communication is preferred.
  21  */
  22
  23 #include <linux/kernel.h>
  24 #include <linux/module.h>
  25 #include <linux/interrupt.h>
  26 #include <linux/i2c.h>
  27 #include <linux/rtc.h>
  28 #include <linux/bcd.h>
  29 #include <linux/mutex.h>
  30 #include <linux/workqueue.h>
  31
  32 #define DS1374_REG_TOD0         0x00
  33 #define DS1374_REG_TOD1         0x01
  34 #define DS1374_REG_TOD2         0x02
  35 #define DS1374_REG_TOD3         0x03
  36 #define DS1374_REG_WDALM0       0x04
  37 #define DS1374_REG_WDALM1       0x05
  38 #define DS1374_REG_WDALM2       0x06
  39 #define DS1374_REG_CR           0x07
  40 #define DS1374_REG_SR           0x08
  41 #define DS1374_REG_SR_OSF       0x80
  42 #define DS1374_REG_TCR          0x09
  43
  44 #define DS1374_DRV_NAME         "ds1374"
  45
  46 static DEFINE_MUTEX(ds1374_mutex);
  47
  48 static struct i2c_driver ds1374_driver;
  49 static struct i2c_client *save_client;
  50
  51 static unsigned short ignore[] = { I2C_CLIENT_END };
  52 static unsigned short normal_addr[] = { 0x68, I2C_CLIENT_END };
  53
  54 static struct i2c_client_address_data addr_data = {
  55         .normal_i2c = normal_addr,
  56         .probe = ignore,
  57         .ignore = ignore,
  58 };
  59
  60 static ulong ds1374_read_rtc(void)
  61 {
  62         ulong time = 0;
  63         int reg = DS1374_REG_WDALM0;
  64
  65         while (reg--) {
  66                 s32 tmp;
  67                 if ((tmp = i2c_smbus_read_byte_data(save_client, reg)) < 0) {
  68                         dev_warn(&save_client->dev,
  69                                  "can't read from rtc chip\n");
  70                         return 0;
  71                 }
  72                 time = (time << 8) | (tmp & 0xff);
  73         }
  74         return time;
  75 }
  76
  77 static void ds1374_write_rtc(ulong time)
  78 {
  79         int reg;
  80
  81         for (reg = DS1374_REG_TOD0; reg < DS1374_REG_WDALM0; reg++) {
  82                 if (i2c_smbus_write_byte_data(save_client, reg, time & 0xff)
  83                     < 0) {
  84                         dev_warn(&save_client->dev,
  85                                  "can't write to rtc chip\n");
  86                         break;
  87                 }
  88                 time = time >> 8;
  89         }
  90 }
  91
  92 static void ds1374_check_rtc_status(void)
  93 {
  94         s32 tmp;
  95
  96         tmp = i2c_smbus_read_byte_data(save_client, DS1374_REG_SR);
  97         if (tmp < 0) {
  98                 dev_warn(&save_client->dev,
  99                          "can't read status from rtc chip\n");
 100                 return;
 101         }
 102         if (tmp & DS1374_REG_SR_OSF) {
 103                 dev_warn(&save_client->dev,
 104                          "oscillator discontinuity flagged, time unreliable\n");
 105                 tmp &= ~DS1374_REG_SR_OSF;
 106                 tmp = i2c_smbus_write_byte_data(save_client, DS1374_REG_SR,
 107                                                 tmp & 0xff);
 108                 if (tmp < 0)
 109                         dev_warn(&save_client->dev,
 110                                  "can't clear discontinuity notification\n");
 111         }
 112 }
 113
 114 ulong ds1374_get_rtc_time(void)
 115 {
 116         ulong t1, t2;
 117         int limit = 10;         /* arbitrary retry limit */
 118
 119         mutex_lock(&ds1374_mutex);
 120
 121         /*
 122          * Since the reads are being performed one byte at a time using
 123          * the SMBus vs a 4-byte i2c transfer, there is a chance that a
 124          * carry will occur during the read. To detect this, 2 reads are
 125          * performed and compared.
 126          */
 127         do {
 128                 t1 = ds1374_read_rtc();
 129                 t2 = ds1374_read_rtc();
 130         } while (t1 != t2 && limit--);
 131
 132         mutex_unlock(&ds1374_mutex);
 133
 134         if (t1 != t2) {
 135                 dev_warn(&save_client->dev,
 136                          "can't get consistent time from rtc chip\n");
 137                 t1 = 0;
 138         }
 139
 140         return t1;
 141 }
 142
 143 static ulong new_time;
 144
 145 static void ds1374_set_work(struct work_struct *work)
 146 {
 147         ulong t1, t2;
 148         int limit = 10;         /* arbitrary retry limit */
 149
 150         t1 = new_time;
 151
 152         mutex_lock(&ds1374_mutex);
 153
 154         /*
 155          * Since the writes are being performed one byte at a time using
 156          * the SMBus vs a 4-byte i2c transfer, there is a chance that a
 157          * carry will occur during the write. To detect this, the write
 158          * value is read back and compared.
 159          */
 160         do {
 161                 ds1374_write_rtc(t1);
 162                 t2 = ds1374_read_rtc();
 163         } while (t1 != t2 && limit--);
 164
 165         mutex_unlock(&ds1374_mutex);
 166
 167         if (t1 != t2)
 168                 dev_warn(&save_client->dev,
 169                          "can't confirm time set from rtc chip\n");
 170 }
 171
 172 static struct workqueue_struct *ds1374_workqueue;
 173
 174 static DECLARE_WORK(ds1374_work, ds1374_set_work);
 175
 176 int ds1374_set_rtc_time(ulong nowtime)
 177 {
 178         new_time = nowtime;
 179
 180         if (in_interrupt())
 181                 queue_work(ds1374_workqueue, &ds1374_work);
 182         else
 183                 ds1374_set_work(NULL);
 184
 185         return 0;
 186 }
 187
 188 /*
 189  *****************************************************************************
 190  *
 191  *      Driver Interface
 192  *
 193  *****************************************************************************
 194  */
 195 static int ds1374_probe(struct i2c_adapter *adap, int addr, int kind)
 196 {
 197         struct i2c_client *client;
 198         int rc;
 199
 200         client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
 201         if (!client)
 202                 return -ENOMEM;
 203
 204         strncpy(client->name, DS1374_DRV_NAME, I2C_NAME_SIZE);
 205         client->addr = addr;
 206         client->adapter = adap;
 207         client->driver = &ds1374_driver;
 208
 209         ds1374_workqueue = create_singlethread_workqueue("ds1374");
 210         if (!ds1374_workqueue) {
 211                 kfree(client);
 212                 return -ENOMEM; /* most expected reason */
 213         }
 214
 215         if ((rc = i2c_attach_client(client)) != 0) {
 216                 kfree(client);
 217                 return rc;
 218         }
 219
 220         save_client = client;
 221
 222         ds1374_check_rtc_status();
 223
 224         return 0;
 225 }
 226
 227 static int ds1374_attach(struct i2c_adapter *adap)
 228 {
 229         return i2c_probe(adap, &addr_data, ds1374_probe);
 230 }
 231
 232 static int ds1374_detach(struct i2c_client *client)
 233 {
 234         int rc;
 235
 236         if ((rc = i2c_detach_client(client)) == 0) {
 237                 kfree(i2c_get_clientdata(client));
 238                 destroy_workqueue(ds1374_workqueue);
 239         }
 240         return rc;
 241 }
 242
 243 static struct i2c_driver ds1374_driver = {
 244         .driver = {
 245                 .name   = DS1374_DRV_NAME,
 246         },
 247         .id = I2C_DRIVERID_DS1374,
 248         .attach_adapter = ds1374_attach,
 249         .detach_client = ds1374_detach,
 250 };
 251
 252 static int __init ds1374_init(void)
 253 {
 254         return i2c_add_driver(&ds1374_driver);
 255 }
 256
 257 static void __exit ds1374_exit(void)
 258 {
 259         i2c_del_driver(&ds1374_driver);
 260 }
 261
 262 module_init(ds1374_init);
 263 module_exit(ds1374_exit);
 264
 265 MODULE_AUTHOR("Randy Vinson <rvinson@mvista.com>");
 266 MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC I2C Client Driver");
 267 MODULE_LICENSE("GPL");