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android-review.linaro.org / kernel / hikey-linaro / bf7ef8f2d57cd1f5f1846dd58ff9309efad58252 / . / drivers / rtc / rtc-max6916.c
blob: 623ab27b2757cda88eb75486a88e87369f0034bc [file] [log] [blame]
Venkat Prashanth B U06776c82016-06-01 11:59:54 +0530[diff] [blame]1/* rtc-max6916.c
2 *
3 * Driver for MAXIM max6916 Low Current, SPI Compatible
4 * Real Time Clock
5 *
6 * Author : Venkat Prashanth B U <venkat.prashanth2498@gmail.com>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 *
12 */
13
14#include <linux/init.h>
15#include <linux/module.h>
16#include <linux/device.h>
17#include <linux/platform_device.h>
18#include <linux/rtc.h>
19#include <linux/spi/spi.h>
20#include <linux/bcd.h>
21
22/* Registers in max6916 rtc */
23
24#define MAX6916_SECONDS_REG 0x01
25#define MAX6916_MINUTES_REG 0x02
26#define MAX6916_HOURS_REG 0x03
27#define MAX6916_DATE_REG 0x04
28#define MAX6916_MONTH_REG 0x05
29#define MAX6916_DAY_REG 0x06
30#define MAX6916_YEAR_REG 0x07
31#define MAX6916_CONTROL_REG 0x08
32#define MAX6916_STATUS_REG 0x0C
33#define MAX6916_CLOCK_BURST 0x3F
34
35static int max6916_read_reg(struct device *dev, unsigned char address,
36 unsigned char *data)
37{
38 struct spi_device *spi = to_spi_device(dev);
39
40 *data = address | 0x80;
41
42 return spi_write_then_read(spi, data, 1, data, 1);
43}
44
45static int max6916_write_reg(struct device *dev, unsigned char address,
46 unsigned char data)
47{
48 struct spi_device *spi = to_spi_device(dev);
49 unsigned char buf[2];
50
51 buf[0] = address & 0x7F;
52 buf[1] = data;
53
54 return spi_write_then_read(spi, buf, 2, NULL, 0);
55}
56
57static int max6916_read_time(struct device *dev, struct rtc_time *dt)
58{
59 struct spi_device *spi = to_spi_device(dev);
60 int err;
61 unsigned char buf[8];
62
63 buf[0] = MAX6916_CLOCK_BURST | 0x80;
64
65 err = spi_write_then_read(spi, buf, 1, buf, 8);
66
67 if (err)
68 return err;
69
70 dt->tm_sec = bcd2bin(buf[0]);
71 dt->tm_min = bcd2bin(buf[1]);
72 dt->tm_hour = bcd2bin(buf[2] & 0x3F);
73 dt->tm_mday = bcd2bin(buf[3]);
74 dt->tm_mon = bcd2bin(buf[4]) - 1;
75 dt->tm_wday = bcd2bin(buf[5]) - 1;
76 dt->tm_year = bcd2bin(buf[6]) + 100;
77
78 return rtc_valid_tm(dt);
79}
80
81static int max6916_set_time(struct device *dev, struct rtc_time *dt)
82{
83 struct spi_device *spi = to_spi_device(dev);
84 unsigned char buf[9];
85
86 if (dt->tm_year < 100 || dt->tm_year > 199) {
87 dev_err(&spi->dev, "Year must be between 2000 and 2099. It's %d.\n",
88 dt->tm_year + 1900);
89 return -EINVAL;
90 }
91
92 buf[0] = MAX6916_CLOCK_BURST & 0x7F;
93 buf[1] = bin2bcd(dt->tm_sec);
94 buf[2] = bin2bcd(dt->tm_min);
95 buf[3] = (bin2bcd(dt->tm_hour) & 0X3F);
96 buf[4] = bin2bcd(dt->tm_mday);
97 buf[5] = bin2bcd(dt->tm_mon + 1);
98 buf[6] = bin2bcd(dt->tm_wday + 1);
99 buf[7] = bin2bcd(dt->tm_year % 100);
100 buf[8] = bin2bcd(0x00);
101
102 /* write the rtc settings */
103 return spi_write_then_read(spi, buf, 9, NULL, 0);
104}
105
106static const struct rtc_class_ops max6916_rtc_ops = {
107 .read_time = max6916_read_time,
108 .set_time = max6916_set_time,
109};
110
111static int max6916_probe(struct spi_device *spi)
112{
113 struct rtc_device *rtc;
114 unsigned char data;
115 int res;
116
117 /* spi setup with max6916 in mode 3 and bits per word as 8 */
118 spi->mode = SPI_MODE_3;
119 spi->bits_per_word = 8;
120 spi_setup(spi);
121
122 /* RTC Settings */
123 res = max6916_read_reg(&spi->dev, MAX6916_SECONDS_REG, &data);
124 if (res)
125 return res;
126
127 /* Disable the write protect of rtc */
128 max6916_read_reg(&spi->dev, MAX6916_CONTROL_REG, &data);
129 data = data & ~(1 << 7);
130 max6916_write_reg(&spi->dev, MAX6916_CONTROL_REG, data);
131
132 /*Enable oscillator,disable oscillator stop flag, glitch filter*/
133 max6916_read_reg(&spi->dev, MAX6916_STATUS_REG, &data);
134 data = data & 0x1B;
135 max6916_write_reg(&spi->dev, MAX6916_STATUS_REG, data);
136
137 /* display the settings */
138 max6916_read_reg(&spi->dev, MAX6916_CONTROL_REG, &data);
139 dev_info(&spi->dev, "MAX6916 RTC CTRL Reg = 0x%02x\n", data);
140
141 max6916_read_reg(&spi->dev, MAX6916_STATUS_REG, &data);
142 dev_info(&spi->dev, "MAX6916 RTC Status Reg = 0x%02x\n", data);
143
144 rtc = devm_rtc_device_register(&spi->dev, "max6916",
145 &max6916_rtc_ops, THIS_MODULE);
146 if (IS_ERR(rtc))
147 return PTR_ERR(rtc);
148
149 spi_set_drvdata(spi, rtc);
150
151 return 0;
152}
153
154static struct spi_driver max6916_driver = {
155 .driver = {
156 .name = "max6916",
157 },
158 .probe = max6916_probe,
159};
160module_spi_driver(max6916_driver);
161
162MODULE_DESCRIPTION("MAX6916 SPI RTC DRIVER");
163MODULE_AUTHOR("Venkat Prashanth B U <venkat.prashanth2498@gmail.com>");
164MODULE_LICENSE("GPL v2");