1 // SPDX-License-Identifier: GPL-2.0-only 2 /* rtc-max6916.c 3 * 4 * Driver for MAXIM max6916 Low Current, SPI Compatible 5 * Real Time Clock 6 * 7 * Author : Venkat Prashanth B U <venkat.prashanth2498@gmail.com> 8 */ 9 10 #include <linux/init.h> 11 #include <linux/module.h> 12 #include <linux/device.h> 13 #include <linux/platform_device.h> 14 #include <linux/rtc.h> 15 #include <linux/spi/spi.h> 16 #include <linux/bcd.h> 17 18 /* Registers in max6916 rtc */ 19 20 #define MAX6916_SECONDS_REG 0x01 21 #define MAX6916_MINUTES_REG 0x02 22 #define MAX6916_HOURS_REG 0x03 23 #define MAX6916_DATE_REG 0x04 24 #define MAX6916_MONTH_REG 0x05 25 #define MAX6916_DAY_REG 0x06 26 #define MAX6916_YEAR_REG 0x07 27 #define MAX6916_CONTROL_REG 0x08 28 #define MAX6916_STATUS_REG 0x0C 29 #define MAX6916_CLOCK_BURST 0x3F 30 max6916_read_reg(struct device * dev,unsigned char address,unsigned char * data)31 static int max6916_read_reg(struct device *dev, unsigned char address, 32 unsigned char *data) 33 { 34 struct spi_device *spi = to_spi_device(dev); 35 36 *data = address | 0x80; 37 38 return spi_write_then_read(spi, data, 1, data, 1); 39 } 40 max6916_write_reg(struct device * dev,unsigned char address,unsigned char data)41 static int max6916_write_reg(struct device *dev, unsigned char address, 42 unsigned char data) 43 { 44 struct spi_device *spi = to_spi_device(dev); 45 unsigned char buf[2]; 46 47 buf[0] = address & 0x7F; 48 buf[1] = data; 49 50 return spi_write_then_read(spi, buf, 2, NULL, 0); 51 } 52 max6916_read_time(struct device * dev,struct rtc_time * dt)53 static int max6916_read_time(struct device *dev, struct rtc_time *dt) 54 { 55 struct spi_device *spi = to_spi_device(dev); 56 int err; 57 unsigned char buf[8]; 58 59 buf[0] = MAX6916_CLOCK_BURST | 0x80; 60 61 err = spi_write_then_read(spi, buf, 1, buf, 8); 62 63 if (err) 64 return err; 65 66 dt->tm_sec = bcd2bin(buf[0]); 67 dt->tm_min = bcd2bin(buf[1]); 68 dt->tm_hour = bcd2bin(buf[2] & 0x3F); 69 dt->tm_mday = bcd2bin(buf[3]); 70 dt->tm_mon = bcd2bin(buf[4]) - 1; 71 dt->tm_wday = bcd2bin(buf[5]) - 1; 72 dt->tm_year = bcd2bin(buf[6]) + 100; 73 74 return 0; 75 } 76 max6916_set_time(struct device * dev,struct rtc_time * dt)77 static int max6916_set_time(struct device *dev, struct rtc_time *dt) 78 { 79 struct spi_device *spi = to_spi_device(dev); 80 unsigned char buf[9]; 81 82 if (dt->tm_year < 100 || dt->tm_year > 199) { 83 dev_err(&spi->dev, "Year must be between 2000 and 2099. It's %d.\n", 84 dt->tm_year + 1900); 85 return -EINVAL; 86 } 87 88 buf[0] = MAX6916_CLOCK_BURST & 0x7F; 89 buf[1] = bin2bcd(dt->tm_sec); 90 buf[2] = bin2bcd(dt->tm_min); 91 buf[3] = (bin2bcd(dt->tm_hour) & 0X3F); 92 buf[4] = bin2bcd(dt->tm_mday); 93 buf[5] = bin2bcd(dt->tm_mon + 1); 94 buf[6] = bin2bcd(dt->tm_wday + 1); 95 buf[7] = bin2bcd(dt->tm_year % 100); 96 buf[8] = bin2bcd(0x00); 97 98 /* write the rtc settings */ 99 return spi_write_then_read(spi, buf, 9, NULL, 0); 100 } 101 102 static const struct rtc_class_ops max6916_rtc_ops = { 103 .read_time = max6916_read_time, 104 .set_time = max6916_set_time, 105 }; 106 max6916_probe(struct spi_device * spi)107 static int max6916_probe(struct spi_device *spi) 108 { 109 struct rtc_device *rtc; 110 unsigned char data; 111 int res; 112 113 /* spi setup with max6916 in mode 3 and bits per word as 8 */ 114 spi->mode = SPI_MODE_3; 115 spi->bits_per_word = 8; 116 spi_setup(spi); 117 118 /* RTC Settings */ 119 res = max6916_read_reg(&spi->dev, MAX6916_SECONDS_REG, &data); 120 if (res) 121 return res; 122 123 /* Disable the write protect of rtc */ 124 max6916_read_reg(&spi->dev, MAX6916_CONTROL_REG, &data); 125 data = data & ~(1 << 7); 126 max6916_write_reg(&spi->dev, MAX6916_CONTROL_REG, data); 127 128 /*Enable oscillator,disable oscillator stop flag, glitch filter*/ 129 max6916_read_reg(&spi->dev, MAX6916_STATUS_REG, &data); 130 data = data & 0x1B; 131 max6916_write_reg(&spi->dev, MAX6916_STATUS_REG, data); 132 133 /* display the settings */ 134 max6916_read_reg(&spi->dev, MAX6916_CONTROL_REG, &data); 135 dev_info(&spi->dev, "MAX6916 RTC CTRL Reg = 0x%02x\n", data); 136 137 max6916_read_reg(&spi->dev, MAX6916_STATUS_REG, &data); 138 dev_info(&spi->dev, "MAX6916 RTC Status Reg = 0x%02x\n", data); 139 140 rtc = devm_rtc_device_register(&spi->dev, "max6916", 141 &max6916_rtc_ops, THIS_MODULE); 142 if (IS_ERR(rtc)) 143 return PTR_ERR(rtc); 144 145 spi_set_drvdata(spi, rtc); 146 147 return 0; 148 } 149 150 static struct spi_driver max6916_driver = { 151 .driver = { 152 .name = "max6916", 153 }, 154 .probe = max6916_probe, 155 }; 156 module_spi_driver(max6916_driver); 157 158 MODULE_DESCRIPTION("MAX6916 SPI RTC DRIVER"); 159 MODULE_AUTHOR("Venkat Prashanth B U <venkat.prashanth2498@gmail.com>"); 160 MODULE_LICENSE("GPL v2"); 161