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