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 0; 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"); 165