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