linux/drivers/rtc/rtc-max6900.c
<<
>>
Prefs
   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * rtc class driver for the Maxim MAX6900 chip
   4 *
   5 * Copyright (c) 2007 MontaVista, Software, Inc.
   6 *
   7 * Author: Dale Farnsworth <dale@farnsworth.org>
   8 *
   9 * based on previously existing rtc class drivers
  10 */
  11
  12#include <linux/module.h>
  13#include <linux/i2c.h>
  14#include <linux/bcd.h>
  15#include <linux/rtc.h>
  16#include <linux/delay.h>
  17
  18/*
  19 * register indices
  20 */
  21#define MAX6900_REG_SC                  0       /* seconds      00-59 */
  22#define MAX6900_REG_MN                  1       /* minutes      00-59 */
  23#define MAX6900_REG_HR                  2       /* hours        00-23 */
  24#define MAX6900_REG_DT                  3       /* day of month 00-31 */
  25#define MAX6900_REG_MO                  4       /* month        01-12 */
  26#define MAX6900_REG_DW                  5       /* day of week   1-7  */
  27#define MAX6900_REG_YR                  6       /* year         00-99 */
  28#define MAX6900_REG_CT                  7       /* control */
  29                                                /* register 8 is undocumented */
  30#define MAX6900_REG_CENTURY             9       /* century */
  31#define MAX6900_REG_LEN                 10
  32
  33#define MAX6900_BURST_LEN               8       /* can burst r/w first 8 regs */
  34
  35#define MAX6900_REG_CT_WP               (1 << 7)        /* Write Protect */
  36
  37/*
  38 * register read/write commands
  39 */
  40#define MAX6900_REG_CONTROL_WRITE       0x8e
  41#define MAX6900_REG_CENTURY_WRITE       0x92
  42#define MAX6900_REG_CENTURY_READ        0x93
  43#define MAX6900_REG_RESERVED_READ       0x96
  44#define MAX6900_REG_BURST_WRITE         0xbe
  45#define MAX6900_REG_BURST_READ          0xbf
  46
  47#define MAX6900_IDLE_TIME_AFTER_WRITE   3       /* specification says 2.5 mS */
  48
  49static struct i2c_driver max6900_driver;
  50
  51static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
  52{
  53        u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };
  54        u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };
  55        struct i2c_msg msgs[4] = {
  56                {
  57                 .addr = client->addr,
  58                 .flags = 0,    /* write */
  59                 .len = sizeof(reg_burst_read),
  60                 .buf = reg_burst_read}
  61                ,
  62                {
  63                 .addr = client->addr,
  64                 .flags = I2C_M_RD,
  65                 .len = MAX6900_BURST_LEN,
  66                 .buf = buf}
  67                ,
  68                {
  69                 .addr = client->addr,
  70                 .flags = 0,    /* write */
  71                 .len = sizeof(reg_century_read),
  72                 .buf = reg_century_read}
  73                ,
  74                {
  75                 .addr = client->addr,
  76                 .flags = I2C_M_RD,
  77                 .len = sizeof(buf[MAX6900_REG_CENTURY]),
  78                 .buf = &buf[MAX6900_REG_CENTURY]
  79                 }
  80        };
  81        int rc;
  82
  83        rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
  84        if (rc != ARRAY_SIZE(msgs)) {
  85                dev_err(&client->dev, "%s: register read failed\n", __func__);
  86                return -EIO;
  87        }
  88        return 0;
  89}
  90
  91static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
  92{
  93        u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE };
  94        struct i2c_msg century_msgs[1] = {
  95                {
  96                 .addr = client->addr,
  97                 .flags = 0,    /* write */
  98                 .len = sizeof(i2c_century_buf),
  99                 .buf = i2c_century_buf}
 100        };
 101        u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE };
 102        struct i2c_msg burst_msgs[1] = {
 103                {
 104                 .addr = client->addr,
 105                 .flags = 0,    /* write */
 106                 .len = sizeof(i2c_burst_buf),
 107                 .buf = i2c_burst_buf}
 108        };
 109        int rc;
 110
 111        /*
 112         * We have to make separate calls to i2c_transfer because of
 113         * the need to delay after each write to the chip.  Also,
 114         * we write the century byte first, since we set the write-protect
 115         * bit as part of the burst write.
 116         */
 117        i2c_century_buf[1] = buf[MAX6900_REG_CENTURY];
 118
 119        rc = i2c_transfer(client->adapter, century_msgs,
 120                          ARRAY_SIZE(century_msgs));
 121        if (rc != ARRAY_SIZE(century_msgs))
 122                goto write_failed;
 123
 124        msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
 125
 126        memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN);
 127
 128        rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs));
 129        if (rc != ARRAY_SIZE(burst_msgs))
 130                goto write_failed;
 131        msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
 132
 133        return 0;
 134
 135 write_failed:
 136        dev_err(&client->dev, "%s: register write failed\n", __func__);
 137        return -EIO;
 138}
 139
 140static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm)
 141{
 142        struct i2c_client *client = to_i2c_client(dev);
 143        int rc;
 144        u8 regs[MAX6900_REG_LEN];
 145
 146        rc = max6900_i2c_read_regs(client, regs);
 147        if (rc < 0)
 148                return rc;
 149
 150        tm->tm_sec = bcd2bin(regs[MAX6900_REG_SC]);
 151        tm->tm_min = bcd2bin(regs[MAX6900_REG_MN]);
 152        tm->tm_hour = bcd2bin(regs[MAX6900_REG_HR] & 0x3f);
 153        tm->tm_mday = bcd2bin(regs[MAX6900_REG_DT]);
 154        tm->tm_mon = bcd2bin(regs[MAX6900_REG_MO]) - 1;
 155        tm->tm_year = bcd2bin(regs[MAX6900_REG_YR]) +
 156                      bcd2bin(regs[MAX6900_REG_CENTURY]) * 100 - 1900;
 157        tm->tm_wday = bcd2bin(regs[MAX6900_REG_DW]);
 158
 159        return 0;
 160}
 161
 162static int max6900_i2c_clear_write_protect(struct i2c_client *client)
 163{
 164        return i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 0);
 165}
 166
 167static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)
 168{
 169        struct i2c_client *client = to_i2c_client(dev);
 170        u8 regs[MAX6900_REG_LEN];
 171        int rc;
 172
 173        rc = max6900_i2c_clear_write_protect(client);
 174        if (rc < 0)
 175                return rc;
 176
 177        regs[MAX6900_REG_SC] = bin2bcd(tm->tm_sec);
 178        regs[MAX6900_REG_MN] = bin2bcd(tm->tm_min);
 179        regs[MAX6900_REG_HR] = bin2bcd(tm->tm_hour);
 180        regs[MAX6900_REG_DT] = bin2bcd(tm->tm_mday);
 181        regs[MAX6900_REG_MO] = bin2bcd(tm->tm_mon + 1);
 182        regs[MAX6900_REG_DW] = bin2bcd(tm->tm_wday);
 183        regs[MAX6900_REG_YR] = bin2bcd(tm->tm_year % 100);
 184        regs[MAX6900_REG_CENTURY] = bin2bcd((tm->tm_year + 1900) / 100);
 185        /* set write protect */
 186        regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;
 187
 188        rc = max6900_i2c_write_regs(client, regs);
 189        if (rc < 0)
 190                return rc;
 191
 192        return 0;
 193}
 194
 195static const struct rtc_class_ops max6900_rtc_ops = {
 196        .read_time = max6900_rtc_read_time,
 197        .set_time = max6900_rtc_set_time,
 198};
 199
 200static int
 201max6900_probe(struct i2c_client *client, const struct i2c_device_id *id)
 202{
 203        struct rtc_device *rtc;
 204
 205        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 206                return -ENODEV;
 207
 208        rtc = devm_rtc_device_register(&client->dev, max6900_driver.driver.name,
 209                                        &max6900_rtc_ops, THIS_MODULE);
 210        if (IS_ERR(rtc))
 211                return PTR_ERR(rtc);
 212
 213        i2c_set_clientdata(client, rtc);
 214
 215        return 0;
 216}
 217
 218static const struct i2c_device_id max6900_id[] = {
 219        { "max6900", 0 },
 220        { }
 221};
 222MODULE_DEVICE_TABLE(i2c, max6900_id);
 223
 224static struct i2c_driver max6900_driver = {
 225        .driver = {
 226                   .name = "rtc-max6900",
 227                   },
 228        .probe = max6900_probe,
 229        .id_table = max6900_id,
 230};
 231
 232module_i2c_driver(max6900_driver);
 233
 234MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
 235MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>");
 236MODULE_LICENSE("GPL");
 237