// SPDX-License-Identifier: GPL-2.0-only /* rtc-max6916.c * * Driver for MAXIM max6916 Low Current, SPI Compatible * Real Time Clock * * Author : Venkat Prashanth B U <venkat.prashanth2498@gmail.com> */ #include <linux/init.h> #include <linux/module.h> #include <linux/device.h> #include <linux/platform_device.h> #include <linux/rtc.h> #include <linux/spi/spi.h> #include <linux/bcd.h> /* Registers in max6916 rtc */ #define MAX6916_SECONDS_REG 0x01 #define MAX6916_MINUTES_REG 0x02 #define MAX6916_HOURS_REG 0x03 #define MAX6916_DATE_REG 0x04 #define MAX6916_MONTH_REG 0x05 #define MAX6916_DAY_REG 0x06 #define MAX6916_YEAR_REG 0x07 #define MAX6916_CONTROL_REG 0x08 #define MAX6916_STATUS_REG 0x0C #define MAX6916_CLOCK_BURST 0x3F static int max6916_read_reg(struct device *dev, unsigned char address, unsigned char *data) { struct spi_device *spi = to_spi_device(dev); *data = address | 0x80; return spi_write_then_read(spi, data, 1, data, 1); } static int max6916_write_reg(struct device *dev, unsigned char address, unsigned char data) { struct spi_device *spi = to_spi_device(dev); unsigned char buf[2]; buf[0] = address & 0x7F; buf[1] = data; return spi_write_then_read(spi, buf, 2, NULL, 0); } static int max6916_read_time(struct device *dev, struct rtc_time *dt) { struct spi_device *spi = to_spi_device(dev); int err; unsigned char buf[8]; buf[0] = MAX6916_CLOCK_BURST | 0x80; err = spi_write_then_read(spi, buf, 1, buf, 8); if (err) return err; dt->tm_sec = bcd2bin(buf[0]); dt->tm_min = bcd2bin(buf[1]); dt->tm_hour = bcd2bin(buf[2] & 0x3F); dt->tm_mday = bcd2bin(buf[3]); dt->tm_mon = bcd2bin(buf[4]) - 1; dt->tm_wday = bcd2bin(buf[5]) - 1; dt->tm_year = bcd2bin(buf[6]) + 100; return 0; } static int max6916_set_time(struct device *dev, struct rtc_time *dt) { struct spi_device *spi = to_spi_device(dev); unsigned char buf[9]; if (dt->tm_year < 100 || dt->tm_year > 199) { dev_err(&spi->dev, "Year must be between 2000 and 2099. It's %d.\n", dt->tm_year + 1900); return -EINVAL; } buf[0] = MAX6916_CLOCK_BURST & 0x7F; buf[1] = bin2bcd(dt->tm_sec); buf[2] = bin2bcd(dt->tm_min); buf[3] = (bin2bcd(dt->tm_hour) & 0X3F); buf[4] = bin2bcd(dt->tm_mday); buf[5] = bin2bcd(dt->tm_mon + 1); buf[6] = bin2bcd(dt->tm_wday + 1); buf[7] = bin2bcd(dt->tm_year % 100); buf[8] = bin2bcd(0x00); /* write the rtc settings */ return spi_write_then_read(spi, buf, 9, NULL, 0); } static const struct rtc_class_ops max6916_rtc_ops = { .read_time = max6916_read_time, .set_time = max6916_set_time, }; static int max6916_probe(struct spi_device *spi) { struct rtc_device *rtc; unsigned char data; int res; /* spi setup with max6916 in mode 3 and bits per word as 8 */ spi->mode = SPI_MODE_3; spi->bits_per_word = 8; spi_setup(spi); /* RTC Settings */ res = max6916_read_reg(&spi->dev, MAX6916_SECONDS_REG, &data); if (res) return res; /* Disable the write protect of rtc */ max6916_read_reg(&spi->dev, MAX6916_CONTROL_REG, &data); data = data & ~(1 << 7); max6916_write_reg(&spi->dev, MAX6916_CONTROL_REG, data); /*Enable oscillator,disable oscillator stop flag, glitch filter*/ max6916_read_reg(&spi->dev, MAX6916_STATUS_REG, &data); data = data & 0x1B; max6916_write_reg(&spi->dev, MAX6916_STATUS_REG, data); /* display the settings */ max6916_read_reg(&spi->dev, MAX6916_CONTROL_REG, &data); dev_info(&spi->dev, "MAX6916 RTC CTRL Reg = 0x%02x\n", data); max6916_read_reg(&spi->dev, MAX6916_STATUS_REG, &data); dev_info(&spi->dev, "MAX6916 RTC Status Reg = 0x%02x\n", data); rtc = devm_rtc_device_register(&spi->dev, "max6916", &max6916_rtc_ops, THIS_MODULE); if (IS_ERR(rtc)) return PTR_ERR(rtc); spi_set_drvdata(spi, rtc); return 0; } static struct spi_driver max6916_driver = { .driver = { .name = "max6916", }, .probe = max6916_probe, }; module_spi_driver(max6916_driver); MODULE_DESCRIPTION("MAX6916 SPI RTC DRIVER"); MODULE_AUTHOR("Venkat Prashanth B U <venkat.prashanth2498@gmail.com>"); MODULE_LICENSE("GPL v2");