drivers/rtc/rtc-max6900.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * rtc class driver for the Maxim MAX6900 chip
0004  *
0005  * Copyright (c) 2007 MontaVista, Software, Inc.
0006  *
0007  * Author: Dale Farnsworth <dale@farnsworth.org>
0008  *
0009  * based on previously existing rtc class drivers
0010  */
0011
0012 #include <linux/module.h>
0013 #include <linux/i2c.h>
0014 #include <linux/bcd.h>
0015 #include <linux/rtc.h>
0016 #include <linux/delay.h>
0017
0018 /*
0019  * register indices
0020  */
0021 #define MAX6900_REG_SC          0   /* seconds      00-59 */
0022 #define MAX6900_REG_MN          1   /* minutes      00-59 */
0023 #define MAX6900_REG_HR          2   /* hours        00-23 */
0024 #define MAX6900_REG_DT          3   /* day of month 00-31 */
0025 #define MAX6900_REG_MO          4   /* month        01-12 */
0026 #define MAX6900_REG_DW          5   /* day of week   1-7  */
0027 #define MAX6900_REG_YR          6   /* year         00-99 */
0028 #define MAX6900_REG_CT          7   /* control */
0029                         /* register 8 is undocumented */
0030 #define MAX6900_REG_CENTURY     9   /* century */
0031 #define MAX6900_REG_LEN         10
0032
0033 #define MAX6900_BURST_LEN       8   /* can burst r/w first 8 regs */
0034
0035 #define MAX6900_REG_CT_WP       (1 << 7)    /* Write Protect */
0036
0037 /*
0038  * register read/write commands
0039  */
0040 #define MAX6900_REG_CONTROL_WRITE   0x8e
0041 #define MAX6900_REG_CENTURY_WRITE   0x92
0042 #define MAX6900_REG_CENTURY_READ    0x93
0043 #define MAX6900_REG_RESERVED_READ   0x96
0044 #define MAX6900_REG_BURST_WRITE     0xbe
0045 #define MAX6900_REG_BURST_READ      0xbf
0046
0047 #define MAX6900_IDLE_TIME_AFTER_WRITE   3   /* specification says 2.5 mS */
0048
0049 static struct i2c_driver max6900_driver;
0050
0051 static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
0052 {
0053     u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };
0054     u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };
0055     struct i2c_msg msgs[4] = {
0056         {
0057          .addr = client->addr,
0058          .flags = 0,    /* write */
0059          .len = sizeof(reg_burst_read),
0060          .buf = reg_burst_read}
0061         ,
0062         {
0063          .addr = client->addr,
0064          .flags = I2C_M_RD,
0065          .len = MAX6900_BURST_LEN,
0066          .buf = buf}
0067         ,
0068         {
0069          .addr = client->addr,
0070          .flags = 0,    /* write */
0071          .len = sizeof(reg_century_read),
0072          .buf = reg_century_read}
0073         ,
0074         {
0075          .addr = client->addr,
0076          .flags = I2C_M_RD,
0077          .len = sizeof(buf[MAX6900_REG_CENTURY]),
0078          .buf = &buf[MAX6900_REG_CENTURY]
0079          }
0080     };
0081     int rc;
0082
0083     rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
0084     if (rc != ARRAY_SIZE(msgs)) {
0085         dev_err(&client->dev, "%s: register read failed\n", __func__);
0086         return -EIO;
0087     }
0088     return 0;
0089 }
0090
0091 static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
0092 {
0093     u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE };
0094     struct i2c_msg century_msgs[1] = {
0095         {
0096          .addr = client->addr,
0097          .flags = 0,    /* write */
0098          .len = sizeof(i2c_century_buf),
0099          .buf = i2c_century_buf}
0100     };
0101     u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE };
0102     struct i2c_msg burst_msgs[1] = {
0103         {
0104          .addr = client->addr,
0105          .flags = 0,    /* write */
0106          .len = sizeof(i2c_burst_buf),
0107          .buf = i2c_burst_buf}
0108     };
0109     int rc;
0110
0111     /*
0112      * We have to make separate calls to i2c_transfer because of
0113      * the need to delay after each write to the chip.  Also,
0114      * we write the century byte first, since we set the write-protect
0115      * bit as part of the burst write.
0116      */
0117     i2c_century_buf[1] = buf[MAX6900_REG_CENTURY];
0118
0119     rc = i2c_transfer(client->adapter, century_msgs,
0120               ARRAY_SIZE(century_msgs));
0121     if (rc != ARRAY_SIZE(century_msgs))
0122         goto write_failed;
0123
0124     msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
0125
0126     memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN);
0127
0128     rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs));
0129     if (rc != ARRAY_SIZE(burst_msgs))
0130         goto write_failed;
0131     msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
0132
0133     return 0;
0134
0135  write_failed:
0136     dev_err(&client->dev, "%s: register write failed\n", __func__);
0137     return -EIO;
0138 }
0139
0140 static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm)
0141 {
0142     struct i2c_client *client = to_i2c_client(dev);
0143     int rc;
0144     u8 regs[MAX6900_REG_LEN];
0145
0146     rc = max6900_i2c_read_regs(client, regs);
0147     if (rc < 0)
0148         return rc;
0149
0150     tm->tm_sec = bcd2bin(regs[MAX6900_REG_SC]);
0151     tm->tm_min = bcd2bin(regs[MAX6900_REG_MN]);
0152     tm->tm_hour = bcd2bin(regs[MAX6900_REG_HR] & 0x3f);
0153     tm->tm_mday = bcd2bin(regs[MAX6900_REG_DT]);
0154     tm->tm_mon = bcd2bin(regs[MAX6900_REG_MO]) - 1;
0155     tm->tm_year = bcd2bin(regs[MAX6900_REG_YR]) +
0156               bcd2bin(regs[MAX6900_REG_CENTURY]) * 100 - 1900;
0157     tm->tm_wday = bcd2bin(regs[MAX6900_REG_DW]);
0158
0159     return 0;
0160 }
0161
0162 static int max6900_i2c_clear_write_protect(struct i2c_client *client)
0163 {
0164     return i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 0);
0165 }
0166
0167 static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)
0168 {
0169     struct i2c_client *client = to_i2c_client(dev);
0170     u8 regs[MAX6900_REG_LEN];
0171     int rc;
0172
0173     rc = max6900_i2c_clear_write_protect(client);
0174     if (rc < 0)
0175         return rc;
0176
0177     regs[MAX6900_REG_SC] = bin2bcd(tm->tm_sec);
0178     regs[MAX6900_REG_MN] = bin2bcd(tm->tm_min);
0179     regs[MAX6900_REG_HR] = bin2bcd(tm->tm_hour);
0180     regs[MAX6900_REG_DT] = bin2bcd(tm->tm_mday);
0181     regs[MAX6900_REG_MO] = bin2bcd(tm->tm_mon + 1);
0182     regs[MAX6900_REG_DW] = bin2bcd(tm->tm_wday);
0183     regs[MAX6900_REG_YR] = bin2bcd(tm->tm_year % 100);
0184     regs[MAX6900_REG_CENTURY] = bin2bcd((tm->tm_year + 1900) / 100);
0185     /* set write protect */
0186     regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;
0187
0188     rc = max6900_i2c_write_regs(client, regs);
0189     if (rc < 0)
0190         return rc;
0191
0192     return 0;
0193 }
0194
0195 static const struct rtc_class_ops max6900_rtc_ops = {
0196     .read_time = max6900_rtc_read_time,
0197     .set_time = max6900_rtc_set_time,
0198 };
0199
0200 static int max6900_probe(struct i2c_client *client)
0201 {
0202     struct rtc_device *rtc;
0203
0204     if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
0205         return -ENODEV;
0206
0207     rtc = devm_rtc_device_register(&client->dev, max6900_driver.driver.name,
0208                     &max6900_rtc_ops, THIS_MODULE);
0209     if (IS_ERR(rtc))
0210         return PTR_ERR(rtc);
0211
0212     i2c_set_clientdata(client, rtc);
0213
0214     return 0;
0215 }
0216
0217 static const struct i2c_device_id max6900_id[] = {
0218     { "max6900", 0 },
0219     { }
0220 };
0221 MODULE_DEVICE_TABLE(i2c, max6900_id);
0222
0223 static struct i2c_driver max6900_driver = {
0224     .driver = {
0225            .name = "rtc-max6900",
0226            },
0227     .probe_new = max6900_probe,
0228     .id_table = max6900_id,
0229 };
0230
0231 module_i2c_driver(max6900_driver);
0232
0233 MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
0234 MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>");
0235 MODULE_LICENSE("GPL");