linux/drivers/rtc/rtc-pcf8583.c
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   1/*
   2 *  drivers/rtc/rtc-pcf8583.c
   3 *
   4 *  Copyright (C) 2000 Russell King
   5 *  Copyright (C) 2008 Wolfram Sang & Juergen Beisert, Pengutronix
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 as
   9 * published by the Free Software Foundation.
  10 *
  11 *  Driver for PCF8583 RTC & RAM chip
  12 *
  13 *  Converted to the generic RTC susbsystem by G. Liakhovetski (2006)
  14 */
  15#include <linux/module.h>
  16#include <linux/i2c.h>
  17#include <linux/slab.h>
  18#include <linux/rtc.h>
  19#include <linux/init.h>
  20#include <linux/err.h>
  21#include <linux/errno.h>
  22#include <linux/bcd.h>
  23
  24struct rtc_mem {
  25        unsigned int    loc;
  26        unsigned int    nr;
  27        unsigned char   *data;
  28};
  29
  30struct pcf8583 {
  31        struct rtc_device *rtc;
  32        unsigned char ctrl;
  33};
  34
  35#define CTRL_STOP       0x80
  36#define CTRL_HOLD       0x40
  37#define CTRL_32KHZ      0x00
  38#define CTRL_MASK       0x08
  39#define CTRL_ALARMEN    0x04
  40#define CTRL_ALARM      0x02
  41#define CTRL_TIMER      0x01
  42
  43
  44static struct i2c_driver pcf8583_driver;
  45
  46#define get_ctrl(x)    ((struct pcf8583 *)i2c_get_clientdata(x))->ctrl
  47#define set_ctrl(x, v) get_ctrl(x) = v
  48
  49#define CMOS_YEAR       (64 + 128)
  50#define CMOS_CHECKSUM   (63)
  51
  52static int pcf8583_get_datetime(struct i2c_client *client, struct rtc_time *dt)
  53{
  54        unsigned char buf[8], addr[1] = { 1 };
  55        struct i2c_msg msgs[2] = {
  56                {
  57                        .addr = client->addr,
  58                        .flags = 0,
  59                        .len = 1,
  60                        .buf = addr,
  61                }, {
  62                        .addr = client->addr,
  63                        .flags = I2C_M_RD,
  64                        .len = 6,
  65                        .buf = buf,
  66                }
  67        };
  68        int ret;
  69
  70        memset(buf, 0, sizeof(buf));
  71
  72        ret = i2c_transfer(client->adapter, msgs, 2);
  73        if (ret == 2) {
  74                dt->tm_year = buf[4] >> 6;
  75                dt->tm_wday = buf[5] >> 5;
  76
  77                buf[4] &= 0x3f;
  78                buf[5] &= 0x1f;
  79
  80                dt->tm_sec = bcd2bin(buf[1]);
  81                dt->tm_min = bcd2bin(buf[2]);
  82                dt->tm_hour = bcd2bin(buf[3]);
  83                dt->tm_mday = bcd2bin(buf[4]);
  84                dt->tm_mon = bcd2bin(buf[5]) - 1;
  85        }
  86
  87        return ret == 2 ? 0 : -EIO;
  88}
  89
  90static int pcf8583_set_datetime(struct i2c_client *client, struct rtc_time *dt, int datetoo)
  91{
  92        unsigned char buf[8];
  93        int ret, len = 6;
  94
  95        buf[0] = 0;
  96        buf[1] = get_ctrl(client) | 0x80;
  97        buf[2] = 0;
  98        buf[3] = bin2bcd(dt->tm_sec);
  99        buf[4] = bin2bcd(dt->tm_min);
 100        buf[5] = bin2bcd(dt->tm_hour);
 101
 102        if (datetoo) {
 103                len = 8;
 104                buf[6] = bin2bcd(dt->tm_mday) | (dt->tm_year << 6);
 105                buf[7] = bin2bcd(dt->tm_mon + 1)  | (dt->tm_wday << 5);
 106        }
 107
 108        ret = i2c_master_send(client, (char *)buf, len);
 109        if (ret != len)
 110                return -EIO;
 111
 112        buf[1] = get_ctrl(client);
 113        ret = i2c_master_send(client, (char *)buf, 2);
 114
 115        return ret == 2 ? 0 : -EIO;
 116}
 117
 118static int pcf8583_get_ctrl(struct i2c_client *client, unsigned char *ctrl)
 119{
 120        *ctrl = get_ctrl(client);
 121        return 0;
 122}
 123
 124static int pcf8583_set_ctrl(struct i2c_client *client, unsigned char *ctrl)
 125{
 126        unsigned char buf[2];
 127
 128        buf[0] = 0;
 129        buf[1] = *ctrl;
 130        set_ctrl(client, *ctrl);
 131
 132        return i2c_master_send(client, (char *)buf, 2);
 133}
 134
 135static int pcf8583_read_mem(struct i2c_client *client, struct rtc_mem *mem)
 136{
 137        unsigned char addr[1];
 138        struct i2c_msg msgs[2] = {
 139                {
 140                        .addr = client->addr,
 141                        .flags = 0,
 142                        .len = 1,
 143                        .buf = addr,
 144                }, {
 145                        .addr = client->addr,
 146                        .flags = I2C_M_RD,
 147                        .len = mem->nr,
 148                        .buf = mem->data,
 149                }
 150        };
 151
 152        if (mem->loc < 8)
 153                return -EINVAL;
 154
 155        addr[0] = mem->loc;
 156
 157        return i2c_transfer(client->adapter, msgs, 2) == 2 ? 0 : -EIO;
 158}
 159
 160static int pcf8583_write_mem(struct i2c_client *client, struct rtc_mem *mem)
 161{
 162        unsigned char buf[9];
 163        int ret;
 164
 165        if (mem->loc < 8 || mem->nr > 8)
 166                return -EINVAL;
 167
 168        buf[0] = mem->loc;
 169        memcpy(buf + 1, mem->data, mem->nr);
 170
 171        ret = i2c_master_send(client, buf, mem->nr + 1);
 172        return ret == mem->nr + 1 ? 0 : -EIO;
 173}
 174
 175static int pcf8583_rtc_read_time(struct device *dev, struct rtc_time *tm)
 176{
 177        struct i2c_client *client = to_i2c_client(dev);
 178        unsigned char ctrl, year[2];
 179        struct rtc_mem mem = { CMOS_YEAR, sizeof(year), year };
 180        int real_year, year_offset, err;
 181
 182        /*
 183         * Ensure that the RTC is running.
 184         */
 185        pcf8583_get_ctrl(client, &ctrl);
 186        if (ctrl & (CTRL_STOP | CTRL_HOLD)) {
 187                unsigned char new_ctrl = ctrl & ~(CTRL_STOP | CTRL_HOLD);
 188
 189                dev_warn(dev, "resetting control %02x -> %02x\n",
 190                        ctrl, new_ctrl);
 191
 192                err = pcf8583_set_ctrl(client, &new_ctrl);
 193                if (err < 0)
 194                        return err;
 195        }
 196
 197        if (pcf8583_get_datetime(client, tm) ||
 198            pcf8583_read_mem(client, &mem))
 199                return -EIO;
 200
 201        real_year = year[0];
 202
 203        /*
 204         * The RTC year holds the LSB two bits of the current
 205         * year, which should reflect the LSB two bits of the
 206         * CMOS copy of the year.  Any difference indicates
 207         * that we have to correct the CMOS version.
 208         */
 209        year_offset = tm->tm_year - (real_year & 3);
 210        if (year_offset < 0)
 211                /*
 212                 * RTC year wrapped.  Adjust it appropriately.
 213                 */
 214                year_offset += 4;
 215
 216        tm->tm_year = (real_year + year_offset + year[1] * 100) - 1900;
 217
 218        return 0;
 219}
 220
 221static int pcf8583_rtc_set_time(struct device *dev, struct rtc_time *tm)
 222{
 223        struct i2c_client *client = to_i2c_client(dev);
 224        unsigned char year[2], chk;
 225        struct rtc_mem cmos_year  = { CMOS_YEAR, sizeof(year), year };
 226        struct rtc_mem cmos_check = { CMOS_CHECKSUM, 1, &chk };
 227        unsigned int proper_year = tm->tm_year + 1900;
 228        int ret;
 229
 230        /*
 231         * The RTC's own 2-bit year must reflect the least
 232         * significant two bits of the CMOS year.
 233         */
 234
 235        ret = pcf8583_set_datetime(client, tm, 1);
 236        if (ret)
 237                return ret;
 238
 239        ret = pcf8583_read_mem(client, &cmos_check);
 240        if (ret)
 241                return ret;
 242
 243        ret = pcf8583_read_mem(client, &cmos_year);
 244        if (ret)
 245                return ret;
 246
 247        chk -= year[1] + year[0];
 248
 249        year[1] = proper_year / 100;
 250        year[0] = proper_year % 100;
 251
 252        chk += year[1] + year[0];
 253
 254        ret = pcf8583_write_mem(client, &cmos_year);
 255
 256        if (ret)
 257                return ret;
 258
 259        ret = pcf8583_write_mem(client, &cmos_check);
 260
 261        return ret;
 262}
 263
 264static const struct rtc_class_ops pcf8583_rtc_ops = {
 265        .read_time      = pcf8583_rtc_read_time,
 266        .set_time       = pcf8583_rtc_set_time,
 267};
 268
 269static int pcf8583_probe(struct i2c_client *client,
 270                                const struct i2c_device_id *id)
 271{
 272        struct pcf8583 *pcf8583;
 273
 274        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 275                return -ENODEV;
 276
 277        pcf8583 = devm_kzalloc(&client->dev, sizeof(struct pcf8583),
 278                                GFP_KERNEL);
 279        if (!pcf8583)
 280                return -ENOMEM;
 281
 282        i2c_set_clientdata(client, pcf8583);
 283
 284        pcf8583->rtc = devm_rtc_device_register(&client->dev,
 285                                pcf8583_driver.driver.name,
 286                                &pcf8583_rtc_ops, THIS_MODULE);
 287
 288        return PTR_ERR_OR_ZERO(pcf8583->rtc);
 289}
 290
 291static const struct i2c_device_id pcf8583_id[] = {
 292        { "pcf8583", 0 },
 293        { }
 294};
 295MODULE_DEVICE_TABLE(i2c, pcf8583_id);
 296
 297static struct i2c_driver pcf8583_driver = {
 298        .driver = {
 299                .name   = "pcf8583",
 300                .owner  = THIS_MODULE,
 301        },
 302        .probe          = pcf8583_probe,
 303        .id_table       = pcf8583_id,
 304};
 305
 306module_i2c_driver(pcf8583_driver);
 307
 308MODULE_AUTHOR("Russell King");
 309MODULE_DESCRIPTION("PCF8583 I2C RTC driver");
 310MODULE_LICENSE("GPL");
 311
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