cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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rtc-max6916.c (4063B)

      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
     31static 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
     41static 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
     53static 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
     77static 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
    102static const struct rtc_class_ops max6916_rtc_ops = {
    103	.read_time = max6916_read_time,
    104	.set_time = max6916_set_time,
    105};
    106
    107static 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
    150static struct spi_driver max6916_driver = {
    151	.driver = {
    152		.name = "max6916",
    153	},
    154	.probe = max6916_probe,
    155};
    156module_spi_driver(max6916_driver);
    157
    158MODULE_DESCRIPTION("MAX6916 SPI RTC DRIVER");
    159MODULE_AUTHOR("Venkat Prashanth B U <venkat.prashanth2498@gmail.com>");
    160MODULE_LICENSE("GPL v2");