161 lines
4.0 KiB
C
161 lines
4.0 KiB
C
// 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 <venkat.prashanth2498@gmail.com>
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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 <venkat.prashanth2498@gmail.com>");
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MODULE_LICENSE("GPL v2");
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