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 | |
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, txbuf: data, n_tx: 1, rxbuf: data, n_rx: 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, txbuf: buf, n_tx: 2, NULL, n_rx: 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, txbuf: buf, n_tx: 1, rxbuf: buf, n_rx: 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 | |
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); |
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, txbuf: buf, n_tx: 9, NULL, n_rx: 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(dev: &spi->dev, MAX6916_SECONDS_REG, data: &data); |
120 | if (res) |
121 | return res; |
122 | |
123 | /* Disable the write protect of rtc */ |
124 | max6916_read_reg(dev: &spi->dev, MAX6916_CONTROL_REG, data: &data); |
125 | data = data & ~(1 << 7); |
126 | max6916_write_reg(dev: &spi->dev, MAX6916_CONTROL_REG, data); |
127 | |
128 | /*Enable oscillator,disable oscillator stop flag, glitch filter*/ |
129 | max6916_read_reg(dev: &spi->dev, MAX6916_STATUS_REG, data: &data); |
130 | data = data & 0x1B; |
131 | max6916_write_reg(dev: &spi->dev, MAX6916_STATUS_REG, data); |
132 | |
133 | /* display the settings */ |
134 | max6916_read_reg(dev: &spi->dev, MAX6916_CONTROL_REG, data: &data); |
135 | dev_info(&spi->dev, "MAX6916 RTC CTRL Reg = 0x%02x\n" , data); |
136 | |
137 | max6916_read_reg(dev: &spi->dev, MAX6916_STATUS_REG, data: &data); |
138 | dev_info(&spi->dev, "MAX6916 RTC Status Reg = 0x%02x\n" , data); |
139 | |
140 | rtc = devm_rtc_device_register(dev: &spi->dev, name: "max6916" , |
141 | ops: &max6916_rtc_ops, THIS_MODULE); |
142 | if (IS_ERR(ptr: rtc)) |
143 | return PTR_ERR(ptr: rtc); |
144 | |
145 | spi_set_drvdata(spi, data: 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" ); |
161 | |