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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 <[email protected]>
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 <[email protected]>");
160MODULE_LICENSE("GPL v2");