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