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d2912cb1 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
06776c89 VP |
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> | |
06776c89 VP |
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 | ||
31 | static 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 | ||
41 | static 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 | ||
53 | static 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 | ||
22652ba7 | 74 | return 0; |
06776c89 VP |
75 | } |
76 | ||
77 | static 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); | |
725412d9 | 85 | return -EINVAL; |
06776c89 VP |
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 | ||
102 | static const struct rtc_class_ops max6916_rtc_ops = { | |
103 | .read_time = max6916_read_time, | |
104 | .set_time = max6916_set_time, | |
105 | }; | |
106 | ||
107 | static 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 | ||
150 | static struct spi_driver max6916_driver = { | |
151 | .driver = { | |
152 | .name = "max6916", | |
153 | }, | |
154 | .probe = max6916_probe, | |
155 | }; | |
156 | module_spi_driver(max6916_driver); | |
157 | ||
158 | MODULE_DESCRIPTION("MAX6916 SPI RTC DRIVER"); | |
159 | MODULE_AUTHOR("Venkat Prashanth B U <venkat.prashanth2498@gmail.com>"); | |
160 | MODULE_LICENSE("GPL v2"); |