linux/drivers/rtc/rtc-max6900.c
<<
>>
Prefs
   1/*
   2 * rtc class driver for the Maxim MAX6900 chip
   3 *
   4 * Author: Dale Farnsworth <dale@farnsworth.org>
   5 *
   6 * based on previously existing rtc class drivers
   7 *
   8 * 2007 (c) MontaVista, Software, Inc.  This file is licensed under
   9 * the terms of the GNU General Public License version 2.  This program
  10 * is licensed "as is" without any warranty of any kind, whether express
  11 * or implied.
  12 */
  13
  14#include <linux/module.h>
  15#include <linux/i2c.h>
  16#include <linux/bcd.h>
  17#include <linux/rtc.h>
  18#include <linux/delay.h>
  19
  20#define DRV_VERSION "0.2"
  21
  22/*
  23 * register indices
  24 */
  25#define MAX6900_REG_SC                  0       /* seconds      00-59 */
  26#define MAX6900_REG_MN                  1       /* minutes      00-59 */
  27#define MAX6900_REG_HR                  2       /* hours        00-23 */
  28#define MAX6900_REG_DT                  3       /* day of month 00-31 */
  29#define MAX6900_REG_MO                  4       /* month        01-12 */
  30#define MAX6900_REG_DW                  5       /* day of week   1-7  */
  31#define MAX6900_REG_YR                  6       /* year         00-99 */
  32#define MAX6900_REG_CT                  7       /* control */
  33                                                /* register 8 is undocumented */
  34#define MAX6900_REG_CENTURY             9       /* century */
  35#define MAX6900_REG_LEN                 10
  36
  37#define MAX6900_BURST_LEN               8       /* can burst r/w first 8 regs */
  38
  39#define MAX6900_REG_CT_WP               (1 << 7)        /* Write Protect */
  40
  41/*
  42 * register read/write commands
  43 */
  44#define MAX6900_REG_CONTROL_WRITE       0x8e
  45#define MAX6900_REG_CENTURY_WRITE       0x92
  46#define MAX6900_REG_CENTURY_READ        0x93
  47#define MAX6900_REG_RESERVED_READ       0x96
  48#define MAX6900_REG_BURST_WRITE         0xbe
  49#define MAX6900_REG_BURST_READ          0xbf
  50
  51#define MAX6900_IDLE_TIME_AFTER_WRITE   3       /* specification says 2.5 mS */
  52
  53static struct i2c_driver max6900_driver;
  54
  55static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
  56{
  57        u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };
  58        u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };
  59        struct i2c_msg msgs[4] = {
  60                {
  61                 .addr = client->addr,
  62                 .flags = 0,    /* write */
  63                 .len = sizeof(reg_burst_read),
  64                 .buf = reg_burst_read}
  65                ,
  66                {
  67                 .addr = client->addr,
  68                 .flags = I2C_M_RD,
  69                 .len = MAX6900_BURST_LEN,
  70                 .buf = buf}
  71                ,
  72                {
  73                 .addr = client->addr,
  74                 .flags = 0,    /* write */
  75                 .len = sizeof(reg_century_read),
  76                 .buf = reg_century_read}
  77                ,
  78                {
  79                 .addr = client->addr,
  80                 .flags = I2C_M_RD,
  81                 .len = sizeof(buf[MAX6900_REG_CENTURY]),
  82                 .buf = &buf[MAX6900_REG_CENTURY]
  83                 }
  84        };
  85        int rc;
  86
  87        rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
  88        if (rc != ARRAY_SIZE(msgs)) {
  89                dev_err(&client->dev, "%s: register read failed\n", __func__);
  90                return -EIO;
  91        }
  92        return 0;
  93}
  94
  95static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
  96{
  97        u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE };
  98        struct i2c_msg century_msgs[1] = {
  99                {
 100                 .addr = client->addr,
 101                 .flags = 0,    /* write */
 102                 .len = sizeof(i2c_century_buf),
 103                 .buf = i2c_century_buf}
 104        };
 105        u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE };
 106        struct i2c_msg burst_msgs[1] = {
 107                {
 108                 .addr = client->addr,
 109                 .flags = 0,    /* write */
 110                 .len = sizeof(i2c_burst_buf),
 111                 .buf = i2c_burst_buf}
 112        };
 113        int rc;
 114
 115        /*
 116         * We have to make separate calls to i2c_transfer because of
 117         * the need to delay after each write to the chip.  Also,
 118         * we write the century byte first, since we set the write-protect
 119         * bit as part of the burst write.
 120         */
 121        i2c_century_buf[1] = buf[MAX6900_REG_CENTURY];
 122
 123        rc = i2c_transfer(client->adapter, century_msgs,
 124                          ARRAY_SIZE(century_msgs));
 125        if (rc != ARRAY_SIZE(century_msgs))
 126                goto write_failed;
 127
 128        msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
 129
 130        memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN);
 131
 132        rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs));
 133        if (rc != ARRAY_SIZE(burst_msgs))
 134                goto write_failed;
 135        msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
 136
 137        return 0;
 138
 139 write_failed:
 140        dev_err(&client->dev, "%s: register write failed\n", __func__);
 141        return -EIO;
 142}
 143
 144static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
 145{
 146        int rc;
 147        u8 regs[MAX6900_REG_LEN];
 148
 149        rc = max6900_i2c_read_regs(client, regs);
 150        if (rc < 0)
 151                return rc;
 152
 153        tm->tm_sec = bcd2bin(regs[MAX6900_REG_SC]);
 154        tm->tm_min = bcd2bin(regs[MAX6900_REG_MN]);
 155        tm->tm_hour = bcd2bin(regs[MAX6900_REG_HR] & 0x3f);
 156        tm->tm_mday = bcd2bin(regs[MAX6900_REG_DT]);
 157        tm->tm_mon = bcd2bin(regs[MAX6900_REG_MO]) - 1;
 158        tm->tm_year = bcd2bin(regs[MAX6900_REG_YR]) +
 159                      bcd2bin(regs[MAX6900_REG_CENTURY]) * 100 - 1900;
 160        tm->tm_wday = bcd2bin(regs[MAX6900_REG_DW]);
 161
 162        return rtc_valid_tm(tm);
 163}
 164
 165static int max6900_i2c_clear_write_protect(struct i2c_client *client)
 166{
 167        int rc;
 168        rc = i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 0);
 169        if (rc < 0) {
 170                dev_err(&client->dev, "%s: control register write failed\n",
 171                        __func__);
 172                return -EIO;
 173        }
 174        return 0;
 175}
 176
 177static int
 178max6900_i2c_set_time(struct i2c_client *client, struct rtc_time const *tm)
 179{
 180        u8 regs[MAX6900_REG_LEN];
 181        int rc;
 182
 183        rc = max6900_i2c_clear_write_protect(client);
 184        if (rc < 0)
 185                return rc;
 186
 187        regs[MAX6900_REG_SC] = bin2bcd(tm->tm_sec);
 188        regs[MAX6900_REG_MN] = bin2bcd(tm->tm_min);
 189        regs[MAX6900_REG_HR] = bin2bcd(tm->tm_hour);
 190        regs[MAX6900_REG_DT] = bin2bcd(tm->tm_mday);
 191        regs[MAX6900_REG_MO] = bin2bcd(tm->tm_mon + 1);
 192        regs[MAX6900_REG_DW] = bin2bcd(tm->tm_wday);
 193        regs[MAX6900_REG_YR] = bin2bcd(tm->tm_year % 100);
 194        regs[MAX6900_REG_CENTURY] = bin2bcd((tm->tm_year + 1900) / 100);
 195        /* set write protect */
 196        regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;
 197
 198        rc = max6900_i2c_write_regs(client, regs);
 199        if (rc < 0)
 200                return rc;
 201
 202        return 0;
 203}
 204
 205static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm)
 206{
 207        return max6900_i2c_read_time(to_i2c_client(dev), tm);
 208}
 209
 210static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)
 211{
 212        return max6900_i2c_set_time(to_i2c_client(dev), tm);
 213}
 214
 215static int max6900_remove(struct i2c_client *client)
 216{
 217        struct rtc_device *rtc = i2c_get_clientdata(client);
 218
 219        if (rtc)
 220                rtc_device_unregister(rtc);
 221
 222        return 0;
 223}
 224
 225static const struct rtc_class_ops max6900_rtc_ops = {
 226        .read_time = max6900_rtc_read_time,
 227        .set_time = max6900_rtc_set_time,
 228};
 229
 230static int
 231max6900_probe(struct i2c_client *client, const struct i2c_device_id *id)
 232{
 233        struct rtc_device *rtc;
 234
 235        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 236                return -ENODEV;
 237
 238        dev_info(&client->dev, "chip found, driver version " DRV_VERSION "\n");
 239
 240        rtc = rtc_device_register(max6900_driver.driver.name,
 241                                  &client->dev, &max6900_rtc_ops, THIS_MODULE);
 242        if (IS_ERR(rtc))
 243                return PTR_ERR(rtc);
 244
 245        i2c_set_clientdata(client, rtc);
 246
 247        return 0;
 248}
 249
 250static struct i2c_device_id max6900_id[] = {
 251        { "max6900", 0 },
 252        { }
 253};
 254
 255static struct i2c_driver max6900_driver = {
 256        .driver = {
 257                   .name = "rtc-max6900",
 258                   },
 259        .probe = max6900_probe,
 260        .remove = max6900_remove,
 261        .id_table = max6900_id,
 262};
 263
 264module_i2c_driver(max6900_driver);
 265
 266MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
 267MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>");
 268MODULE_LICENSE("GPL");
 269MODULE_VERSION(DRV_VERSION);
 270
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.