Venkat Prashanth B U | 06776c8 | 2016-06-01 11:59:54 +0530 | [diff] [blame] | 1 | /* rtc-max6916.c |
| 2 | * |
| 3 | * Driver for MAXIM max6916 Low Current, SPI Compatible |
| 4 | * Real Time Clock |
| 5 | * |
| 6 | * Author : Venkat Prashanth B U <venkat.prashanth2498@gmail.com> |
| 7 | * |
| 8 | * This program is free software; you can redistribute it and/or modify |
| 9 | * it under the terms of the GNU General Public License version 2 as |
| 10 | * published by the Free Software Foundation. |
| 11 | * |
| 12 | */ |
| 13 | |
| 14 | #include <linux/init.h> |
| 15 | #include <linux/module.h> |
| 16 | #include <linux/device.h> |
| 17 | #include <linux/platform_device.h> |
| 18 | #include <linux/rtc.h> |
| 19 | #include <linux/spi/spi.h> |
| 20 | #include <linux/bcd.h> |
| 21 | |
| 22 | /* Registers in max6916 rtc */ |
| 23 | |
| 24 | #define MAX6916_SECONDS_REG 0x01 |
| 25 | #define MAX6916_MINUTES_REG 0x02 |
| 26 | #define MAX6916_HOURS_REG 0x03 |
| 27 | #define MAX6916_DATE_REG 0x04 |
| 28 | #define MAX6916_MONTH_REG 0x05 |
| 29 | #define MAX6916_DAY_REG 0x06 |
| 30 | #define MAX6916_YEAR_REG 0x07 |
| 31 | #define MAX6916_CONTROL_REG 0x08 |
| 32 | #define MAX6916_STATUS_REG 0x0C |
| 33 | #define MAX6916_CLOCK_BURST 0x3F |
| 34 | |
| 35 | static int max6916_read_reg(struct device *dev, unsigned char address, |
| 36 | unsigned char *data) |
| 37 | { |
| 38 | struct spi_device *spi = to_spi_device(dev); |
| 39 | |
| 40 | *data = address | 0x80; |
| 41 | |
| 42 | return spi_write_then_read(spi, data, 1, data, 1); |
| 43 | } |
| 44 | |
| 45 | static int max6916_write_reg(struct device *dev, unsigned char address, |
| 46 | unsigned char data) |
| 47 | { |
| 48 | struct spi_device *spi = to_spi_device(dev); |
| 49 | unsigned char buf[2]; |
| 50 | |
| 51 | buf[0] = address & 0x7F; |
| 52 | buf[1] = data; |
| 53 | |
| 54 | return spi_write_then_read(spi, buf, 2, NULL, 0); |
| 55 | } |
| 56 | |
| 57 | static int max6916_read_time(struct device *dev, struct rtc_time *dt) |
| 58 | { |
| 59 | struct spi_device *spi = to_spi_device(dev); |
| 60 | int err; |
| 61 | unsigned char buf[8]; |
| 62 | |
| 63 | buf[0] = MAX6916_CLOCK_BURST | 0x80; |
| 64 | |
| 65 | err = spi_write_then_read(spi, buf, 1, buf, 8); |
| 66 | |
| 67 | if (err) |
| 68 | return err; |
| 69 | |
| 70 | dt->tm_sec = bcd2bin(buf[0]); |
| 71 | dt->tm_min = bcd2bin(buf[1]); |
| 72 | dt->tm_hour = bcd2bin(buf[2] & 0x3F); |
| 73 | dt->tm_mday = bcd2bin(buf[3]); |
| 74 | dt->tm_mon = bcd2bin(buf[4]) - 1; |
| 75 | dt->tm_wday = bcd2bin(buf[5]) - 1; |
| 76 | dt->tm_year = bcd2bin(buf[6]) + 100; |
| 77 | |
| 78 | return rtc_valid_tm(dt); |
| 79 | } |
| 80 | |
| 81 | static int max6916_set_time(struct device *dev, struct rtc_time *dt) |
| 82 | { |
| 83 | struct spi_device *spi = to_spi_device(dev); |
| 84 | unsigned char buf[9]; |
| 85 | |
| 86 | if (dt->tm_year < 100 || dt->tm_year > 199) { |
| 87 | dev_err(&spi->dev, "Year must be between 2000 and 2099. It's %d.\n", |
| 88 | dt->tm_year + 1900); |
| 89 | return -EINVAL; |
| 90 | } |
| 91 | |
| 92 | buf[0] = MAX6916_CLOCK_BURST & 0x7F; |
| 93 | buf[1] = bin2bcd(dt->tm_sec); |
| 94 | buf[2] = bin2bcd(dt->tm_min); |
| 95 | buf[3] = (bin2bcd(dt->tm_hour) & 0X3F); |
| 96 | buf[4] = bin2bcd(dt->tm_mday); |
| 97 | buf[5] = bin2bcd(dt->tm_mon + 1); |
| 98 | buf[6] = bin2bcd(dt->tm_wday + 1); |
| 99 | buf[7] = bin2bcd(dt->tm_year % 100); |
| 100 | buf[8] = bin2bcd(0x00); |
| 101 | |
| 102 | /* write the rtc settings */ |
| 103 | return spi_write_then_read(spi, buf, 9, NULL, 0); |
| 104 | } |
| 105 | |
| 106 | static const struct rtc_class_ops max6916_rtc_ops = { |
| 107 | .read_time = max6916_read_time, |
| 108 | .set_time = max6916_set_time, |
| 109 | }; |
| 110 | |
| 111 | static int max6916_probe(struct spi_device *spi) |
| 112 | { |
| 113 | struct rtc_device *rtc; |
| 114 | unsigned char data; |
| 115 | int res; |
| 116 | |
| 117 | /* spi setup with max6916 in mode 3 and bits per word as 8 */ |
| 118 | spi->mode = SPI_MODE_3; |
| 119 | spi->bits_per_word = 8; |
| 120 | spi_setup(spi); |
| 121 | |
| 122 | /* RTC Settings */ |
| 123 | res = max6916_read_reg(&spi->dev, MAX6916_SECONDS_REG, &data); |
| 124 | if (res) |
| 125 | return res; |
| 126 | |
| 127 | /* Disable the write protect of rtc */ |
| 128 | max6916_read_reg(&spi->dev, MAX6916_CONTROL_REG, &data); |
| 129 | data = data & ~(1 << 7); |
| 130 | max6916_write_reg(&spi->dev, MAX6916_CONTROL_REG, data); |
| 131 | |
| 132 | /*Enable oscillator,disable oscillator stop flag, glitch filter*/ |
| 133 | max6916_read_reg(&spi->dev, MAX6916_STATUS_REG, &data); |
| 134 | data = data & 0x1B; |
| 135 | max6916_write_reg(&spi->dev, MAX6916_STATUS_REG, data); |
| 136 | |
| 137 | /* display the settings */ |
| 138 | max6916_read_reg(&spi->dev, MAX6916_CONTROL_REG, &data); |
| 139 | dev_info(&spi->dev, "MAX6916 RTC CTRL Reg = 0x%02x\n", data); |
| 140 | |
| 141 | max6916_read_reg(&spi->dev, MAX6916_STATUS_REG, &data); |
| 142 | dev_info(&spi->dev, "MAX6916 RTC Status Reg = 0x%02x\n", data); |
| 143 | |
| 144 | rtc = devm_rtc_device_register(&spi->dev, "max6916", |
| 145 | &max6916_rtc_ops, THIS_MODULE); |
| 146 | if (IS_ERR(rtc)) |
| 147 | return PTR_ERR(rtc); |
| 148 | |
| 149 | spi_set_drvdata(spi, rtc); |
| 150 | |
| 151 | return 0; |
| 152 | } |
| 153 | |
| 154 | static struct spi_driver max6916_driver = { |
| 155 | .driver = { |
| 156 | .name = "max6916", |
| 157 | }, |
| 158 | .probe = max6916_probe, |
| 159 | }; |
| 160 | module_spi_driver(max6916_driver); |
| 161 | |
| 162 | MODULE_DESCRIPTION("MAX6916 SPI RTC DRIVER"); |
| 163 | MODULE_AUTHOR("Venkat Prashanth B U <venkat.prashanth2498@gmail.com>"); |
| 164 | MODULE_LICENSE("GPL v2"); |