drivers/i2c/chips/ds1374.c

   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 #include <asm/time.h>
  31 #include <asm/rtc.h>
  32
  33 #define DS1374_REG_TOD0         0x00
  34 #define DS1374_REG_TOD1         0x01
  35 #define DS1374_REG_TOD2         0x02
  36 #define DS1374_REG_TOD3         0x03
  37 #define DS1374_REG_WDALM0       0x04
  38 #define DS1374_REG_WDALM1       0x05
  39 #define DS1374_REG_WDALM2       0x06
  40 #define DS1374_REG_CR           0x07
  41 #define DS1374_REG_SR           0x08
  42 #define DS1374_REG_SR_OSF       0x80
  43 #define DS1374_REG_TCR          0x09
  44
  45 #define DS1374_DRV_NAME         "ds1374"
  46
  47 static DECLARE_MUTEX(ds1374_mutex);
  48
  49 static struct i2c_driver ds1374_driver;
  50 static struct i2c_client *save_client;
  51
  52 static unsigned short ignore[] = { I2C_CLIENT_END };
  53 static unsigned short normal_addr[] = { 0x68, I2C_CLIENT_END };
  54
  55 static struct i2c_client_address_data addr_data = {
  56         .normal_i2c = normal_addr,
  57         .normal_i2c_range = ignore,
  58         .probe = ignore,
  59         .probe_range = ignore,
  60         .ignore = ignore,
  61         .ignore_range = ignore,
  62         .force = ignore,
  63 };
  64
  65 static ulong ds1374_read_rtc(void)
  66 {
  67         ulong time = 0;
  68         int reg = DS1374_REG_WDALM0;
  69
  70         while (reg--) {
  71                 s32 tmp;
  72                 if ((tmp = i2c_smbus_read_byte_data(save_client, reg)) < 0) {
  73                         dev_warn(&save_client->dev,
  74                                  "can't read from rtc chip\n");
  75                         return 0;
  76                 }
  77                 time = (time << 8) | (tmp & 0xff);
  78         }
  79         return time;
  80 }
  81
  82 static void ds1374_write_rtc(ulong time)
  83 {
  84         int reg;
  85
  86         for (reg = DS1374_REG_TOD0; reg < DS1374_REG_WDALM0; reg++) {
  87                 if (i2c_smbus_write_byte_data(save_client, reg, time & 0xff)
  88                     < 0) {
  89                         dev_warn(&save_client->dev,
  90                                  "can't write to rtc chip\n");
  91                         break;
  92                 }
  93                 time = time >> 8;
  94         }
  95 }
  96
  97 static void ds1374_check_rtc_status(void)
  98 {
  99         s32 tmp;
 100
 101         tmp = i2c_smbus_read_byte_data(save_client, DS1374_REG_SR);
 102         if (tmp < 0) {
 103                 dev_warn(&save_client->dev,
 104                          "can't read status from rtc chip\n");
 105                 return;
 106         }
 107         if (tmp & DS1374_REG_SR_OSF) {
 108                 dev_warn(&save_client->dev,
 109                          "oscillator discontinuity flagged, time unreliable\n");
 110                 tmp &= ~DS1374_REG_SR_OSF;
 111                 tmp = i2c_smbus_write_byte_data(save_client, DS1374_REG_SR,
 112                                                 tmp & 0xff);
 113                 if (tmp < 0)
 114                         dev_warn(&save_client->dev,
 115                                  "can't clear discontinuity notification\n");
 116         }
 117 }
 118
 119 ulong ds1374_get_rtc_time(void)
 120 {
 121         ulong t1, t2;
 122         int limit = 10;         /* arbitrary retry limit */
 123
 124         down(&ds1374_mutex);
 125
 126         /*
 127          * Since the reads are being performed one byte at a time using
 128          * the SMBus vs a 4-byte i2c transfer, there is a chance that a
 129          * carry will occur during the read. To detect this, 2 reads are
 130          * performed and compared.
 131          */
 132         do {
 133                 t1 = ds1374_read_rtc();
 134                 t2 = ds1374_read_rtc();
 135         } while (t1 != t2 && limit--);
 136
 137         up(&ds1374_mutex);
 138
 139         if (t1 != t2) {
 140                 dev_warn(&save_client->dev,
 141                          "can't get consistent time from rtc chip\n");
 142                 t1 = 0;
 143         }
 144
 145         return t1;
 146 }
 147
 148 static void ds1374_set_tlet(ulong arg)
 149 {
 150         ulong t1, t2;
 151         int limit = 10;         /* arbitrary retry limit */
 152
 153         t1 = *(ulong *) arg;
 154
 155         down(&ds1374_mutex);
 156
 157         /*
 158          * Since the writes are being performed one byte at a time using
 159          * the SMBus vs a 4-byte i2c transfer, there is a chance that a
 160          * carry will occur during the write. To detect this, the write
 161          * value is read back and compared.
 162          */
 163         do {
 164                 ds1374_write_rtc(t1);
 165                 t2 = ds1374_read_rtc();
 166         } while (t1 != t2 && limit--);
 167
 168         up(&ds1374_mutex);
 169
 170         if (t1 != t2)
 171                 dev_warn(&save_client->dev,
 172                          "can't confirm time set from rtc chip\n");
 173 }
 174
 175 ulong new_time;
 176
 177 DECLARE_TASKLET_DISABLED(ds1374_tasklet, ds1374_set_tlet, (ulong) & new_time);
 178
 179 int ds1374_set_rtc_time(ulong nowtime)
 180 {
 181         new_time = nowtime;
 182
 183         if (in_interrupt())
 184                 tasklet_schedule(&ds1374_tasklet);
 185         else
 186                 ds1374_set_tlet((ulong) & new_time);
 187
 188         return 0;
 189 }
 190
 191 /*
 192  *****************************************************************************
 193  *
 194  *      Driver Interface
 195  *
 196  *****************************************************************************
 197  */
 198 static int ds1374_probe(struct i2c_adapter *adap, int addr, int kind)
 199 {
 200         struct i2c_client *client;
 201         int rc;
 202
 203         client = kmalloc(sizeof(struct i2c_client), GFP_KERNEL);
 204         if (!client)
 205                 return -ENOMEM;
 206
 207         memset(client, 0, sizeof(struct i2c_client));
 208         strncpy(client->name, DS1374_DRV_NAME, I2C_NAME_SIZE);
 209         client->flags = I2C_DF_NOTIFY;
 210         client->addr = addr;
 211         client->adapter = adap;
 212         client->driver = &ds1374_driver;
 213
 214         if ((rc = i2c_attach_client(client)) != 0) {
 215                 kfree(client);
 216                 return rc;
 217         }
 218
 219         save_client = client;
 220
 221         ds1374_check_rtc_status();
 222
 223         return 0;
 224 }
 225
 226 static int ds1374_attach(struct i2c_adapter *adap)
 227 {
 228         return i2c_probe(adap, &addr_data, ds1374_probe);
 229 }
 230
 231 static int ds1374_detach(struct i2c_client *client)
 232 {
 233         int rc;
 234
 235         if ((rc = i2c_detach_client(client)) == 0) {
 236                 kfree(i2c_get_clientdata(client));
 237                 tasklet_kill(&ds1374_tasklet);
 238         }
 239         return rc;
 240 }
 241
 242 static struct i2c_driver ds1374_driver = {
 243         .owner = THIS_MODULE,
 244         .name = DS1374_DRV_NAME,
 245         .id = I2C_DRIVERID_DS1374,
 246         .flags = I2C_DF_NOTIFY,
 247         .attach_adapter = ds1374_attach,
 248         .detach_client = ds1374_detach,
 249 };
 250
 251 static int __init ds1374_init(void)
 252 {
 253         return i2c_add_driver(&ds1374_driver);
 254 }
 255
 256 static void __exit ds1374_exit(void)
 257 {
 258         i2c_del_driver(&ds1374_driver);
 259 }
 260
 261 module_init(ds1374_init);
 262 module_exit(ds1374_exit);
 263
 264 MODULE_AUTHOR("Randy Vinson <rvinson@mvista.com>");
 265 MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC I2C Client Driver");
 266 MODULE_LICENSE("GPL");