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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
  31 #define DS1374_REG_TOD0         0x00
  32 #define DS1374_REG_TOD1         0x01
  33 #define DS1374_REG_TOD2         0x02
  34 #define DS1374_REG_TOD3         0x03
  35 #define DS1374_REG_WDALM0       0x04
  36 #define DS1374_REG_WDALM1       0x05
  37 #define DS1374_REG_WDALM2       0x06
  38 #define DS1374_REG_CR           0x07
  39 #define DS1374_REG_SR           0x08
  40 #define DS1374_REG_SR_OSF       0x80
  41 #define DS1374_REG_TCR          0x09
  42
  43 #define DS1374_DRV_NAME         "ds1374"
  44
  45 static DEFINE_MUTEX(ds1374_mutex);
  46
  47 static struct i2c_driver ds1374_driver;
  48 static struct i2c_client *save_client;
  49
  50 static unsigned short ignore[] = { I2C_CLIENT_END };
  51 static unsigned short normal_addr[] = { 0x68, I2C_CLIENT_END };
  52
  53 static struct i2c_client_address_data addr_data = {
  54         .normal_i2c = normal_addr,
  55         .probe = ignore,
  56         .ignore = ignore,
  57 };
  58
  59 static ulong ds1374_read_rtc(void)
  60 {
  61         ulong time = 0;
  62         int reg = DS1374_REG_WDALM0;
  63
  64         while (reg--) {
  65                 s32 tmp;
  66                 if ((tmp = i2c_smbus_read_byte_data(save_client, reg)) < 0) {
  67                         dev_warn(&save_client->dev,
  68                                  "can't read from rtc chip\n");
  69                         return 0;
  70                 }
  71                 time = (time << 8) | (tmp & 0xff);
  72         }
  73         return time;
  74 }
  75
  76 static void ds1374_write_rtc(ulong time)
  77 {
  78         int reg;
  79
  80         for (reg = DS1374_REG_TOD0; reg < DS1374_REG_WDALM0; reg++) {
  81                 if (i2c_smbus_write_byte_data(save_client, reg, time & 0xff)
  82                     < 0) {
  83                         dev_warn(&save_client->dev,
  84                                  "can't write to rtc chip\n");
  85                         break;
  86                 }
  87                 time = time >> 8;
  88         }
  89 }
  90
  91 static void ds1374_check_rtc_status(void)
  92 {
  93         s32 tmp;
  94
  95         tmp = i2c_smbus_read_byte_data(save_client, DS1374_REG_SR);
  96         if (tmp < 0) {
  97                 dev_warn(&save_client->dev,
  98                          "can't read status from rtc chip\n");
  99                 return;
 100         }
 101         if (tmp & DS1374_REG_SR_OSF) {
 102                 dev_warn(&save_client->dev,
 103                          "oscillator discontinuity flagged, time unreliable\n");
 104                 tmp &= ~DS1374_REG_SR_OSF;
 105                 tmp = i2c_smbus_write_byte_data(save_client, DS1374_REG_SR,
 106                                                 tmp & 0xff);
 107                 if (tmp < 0)
 108                         dev_warn(&save_client->dev,
 109                                  "can't clear discontinuity notification\n");
 110         }
 111 }
 112
 113 ulong ds1374_get_rtc_time(void)
 114 {
 115         ulong t1, t2;
 116         int limit = 10;         /* arbitrary retry limit */
 117
 118         mutex_lock(&ds1374_mutex);
 119
 120         /*
 121          * Since the reads are being performed one byte at a time using
 122          * the SMBus vs a 4-byte i2c transfer, there is a chance that a
 123          * carry will occur during the read. To detect this, 2 reads are
 124          * performed and compared.
 125          */
 126         do {
 127                 t1 = ds1374_read_rtc();
 128                 t2 = ds1374_read_rtc();
 129         } while (t1 != t2 && limit--);
 130
 131         mutex_unlock(&ds1374_mutex);
 132
 133         if (t1 != t2) {
 134                 dev_warn(&save_client->dev,
 135                          "can't get consistent time from rtc chip\n");
 136                 t1 = 0;
 137         }
 138
 139         return t1;
 140 }
 141
 142 static void ds1374_set_tlet(ulong arg)
 143 {
 144         ulong t1, t2;
 145         int limit = 10;         /* arbitrary retry limit */
 146
 147         t1 = *(ulong *) arg;
 148
 149         mutex_lock(&ds1374_mutex);
 150
 151         /*
 152          * Since the writes are being performed one byte at a time using
 153          * the SMBus vs a 4-byte i2c transfer, there is a chance that a
 154          * carry will occur during the write. To detect this, the write
 155          * value is read back and compared.
 156          */
 157         do {
 158                 ds1374_write_rtc(t1);
 159                 t2 = ds1374_read_rtc();
 160         } while (t1 != t2 && limit--);
 161
 162         mutex_unlock(&ds1374_mutex);
 163
 164         if (t1 != t2)
 165                 dev_warn(&save_client->dev,
 166                          "can't confirm time set from rtc chip\n");
 167 }
 168
 169 static ulong new_time;
 170
 171 static DECLARE_TASKLET_DISABLED(ds1374_tasklet, ds1374_set_tlet,
 172                                 (ulong) & new_time);
 173
 174 int ds1374_set_rtc_time(ulong nowtime)
 175 {
 176         new_time = nowtime;
 177
 178         if (in_interrupt())
 179                 tasklet_schedule(&ds1374_tasklet);
 180         else
 181                 ds1374_set_tlet((ulong) & new_time);
 182
 183         return 0;
 184 }
 185
 186 /*
 187  *****************************************************************************
 188  *
 189  *      Driver Interface
 190  *
 191  *****************************************************************************
 192  */
 193 static int ds1374_probe(struct i2c_adapter *adap, int addr, int kind)
 194 {
 195         struct i2c_client *client;
 196         int rc;
 197
 198         client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
 199         if (!client)
 200                 return -ENOMEM;
 201
 202         strncpy(client->name, DS1374_DRV_NAME, I2C_NAME_SIZE);
 203         client->addr = addr;
 204         client->adapter = adap;
 205         client->driver = &ds1374_driver;
 206
 207         if ((rc = i2c_attach_client(client)) != 0) {
 208                 kfree(client);
 209                 return rc;
 210         }
 211
 212         save_client = client;
 213
 214         ds1374_check_rtc_status();
 215
 216         return 0;
 217 }
 218
 219 static int ds1374_attach(struct i2c_adapter *adap)
 220 {
 221         return i2c_probe(adap, &addr_data, ds1374_probe);
 222 }
 223
 224 static int ds1374_detach(struct i2c_client *client)
 225 {
 226         int rc;
 227
 228         if ((rc = i2c_detach_client(client)) == 0) {
 229                 kfree(i2c_get_clientdata(client));
 230                 tasklet_kill(&ds1374_tasklet);
 231         }
 232         return rc;
 233 }
 234
 235 static struct i2c_driver ds1374_driver = {
 236         .driver = {
 237                 .name   = DS1374_DRV_NAME,
 238         },
 239         .id = I2C_DRIVERID_DS1374,
 240         .attach_adapter = ds1374_attach,
 241         .detach_client = ds1374_detach,
 242 };
 243
 244 static int __init ds1374_init(void)
 245 {
 246         return i2c_add_driver(&ds1374_driver);
 247 }
 248
 249 static void __exit ds1374_exit(void)
 250 {
 251         i2c_del_driver(&ds1374_driver);
 252 }
 253
 254 module_init(ds1374_init);
 255 module_exit(ds1374_exit);
 256
 257 MODULE_AUTHOR("Randy Vinson <rvinson@mvista.com>");
 258 MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC I2C Client Driver");
 259 MODULE_LICENSE("GPL");