1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* drivers/rtc/rtc-max6902.c |
3 | * |
4 | * Copyright (C) 2006 8D Technologies inc. |
5 | * Copyright (C) 2004 Compulab Ltd. |
6 | * |
7 | * Driver for MAX6902 spi RTC |
8 | */ |
9 | |
10 | #include <linux/module.h> |
11 | #include <linux/kernel.h> |
12 | #include <linux/platform_device.h> |
13 | #include <linux/init.h> |
14 | #include <linux/rtc.h> |
15 | #include <linux/spi/spi.h> |
16 | #include <linux/bcd.h> |
17 | |
18 | #define MAX6902_REG_SECONDS 0x01 |
19 | #define MAX6902_REG_MINUTES 0x03 |
20 | #define MAX6902_REG_HOURS 0x05 |
21 | #define MAX6902_REG_DATE 0x07 |
22 | #define MAX6902_REG_MONTH 0x09 |
23 | #define MAX6902_REG_DAY 0x0B |
24 | #define MAX6902_REG_YEAR 0x0D |
25 | #define MAX6902_REG_CONTROL 0x0F |
26 | #define MAX6902_REG_CENTURY 0x13 |
27 | |
28 | static int max6902_set_reg(struct device *dev, unsigned char address, |
29 | unsigned char data) |
30 | { |
31 | struct spi_device *spi = to_spi_device(dev); |
32 | unsigned char buf[2]; |
33 | |
34 | /* MSB must be '0' to write */ |
35 | buf[0] = address & 0x7f; |
36 | buf[1] = data; |
37 | |
38 | return spi_write_then_read(spi, txbuf: buf, n_tx: 2, NULL, n_rx: 0); |
39 | } |
40 | |
41 | static int max6902_get_reg(struct device *dev, unsigned char address, |
42 | unsigned char *data) |
43 | { |
44 | struct spi_device *spi = to_spi_device(dev); |
45 | |
46 | /* Set MSB to indicate read */ |
47 | *data = address | 0x80; |
48 | |
49 | return spi_write_then_read(spi, txbuf: data, n_tx: 1, rxbuf: data, n_rx: 1); |
50 | } |
51 | |
52 | static int max6902_read_time(struct device *dev, struct rtc_time *dt) |
53 | { |
54 | int err, century; |
55 | struct spi_device *spi = to_spi_device(dev); |
56 | unsigned char buf[8]; |
57 | |
58 | buf[0] = 0xbf; /* Burst read */ |
59 | |
60 | err = spi_write_then_read(spi, txbuf: buf, n_tx: 1, rxbuf: buf, n_rx: 8); |
61 | if (err != 0) |
62 | return err; |
63 | |
64 | /* The chip sends data in this order: |
65 | * Seconds, Minutes, Hours, Date, Month, Day, Year */ |
66 | dt->tm_sec = bcd2bin(buf[0]); |
67 | dt->tm_min = bcd2bin(buf[1]); |
68 | dt->tm_hour = bcd2bin(buf[2]); |
69 | dt->tm_mday = bcd2bin(buf[3]); |
70 | dt->tm_mon = bcd2bin(buf[4]) - 1; |
71 | dt->tm_wday = bcd2bin(buf[5]); |
72 | dt->tm_year = bcd2bin(buf[6]); |
73 | |
74 | /* Read century */ |
75 | err = max6902_get_reg(dev, MAX6902_REG_CENTURY, data: &buf[0]); |
76 | if (err != 0) |
77 | return err; |
78 | |
79 | century = bcd2bin(buf[0]) * 100; |
80 | |
81 | dt->tm_year += century; |
82 | dt->tm_year -= 1900; |
83 | |
84 | return 0; |
85 | } |
86 | |
87 | static int max6902_set_time(struct device *dev, struct rtc_time *dt) |
88 | { |
89 | dt->tm_year = dt->tm_year + 1900; |
90 | |
91 | /* Remove write protection */ |
92 | max6902_set_reg(dev, MAX6902_REG_CONTROL, data: 0); |
93 | |
94 | max6902_set_reg(dev, MAX6902_REG_SECONDS, bin2bcd(dt->tm_sec)); |
95 | max6902_set_reg(dev, MAX6902_REG_MINUTES, bin2bcd(dt->tm_min)); |
96 | max6902_set_reg(dev, MAX6902_REG_HOURS, bin2bcd(dt->tm_hour)); |
97 | |
98 | max6902_set_reg(dev, MAX6902_REG_DATE, bin2bcd(dt->tm_mday)); |
99 | max6902_set_reg(dev, MAX6902_REG_MONTH, bin2bcd(dt->tm_mon + 1)); |
100 | max6902_set_reg(dev, MAX6902_REG_DAY, bin2bcd(dt->tm_wday)); |
101 | max6902_set_reg(dev, MAX6902_REG_YEAR, bin2bcd(dt->tm_year % 100)); |
102 | max6902_set_reg(dev, MAX6902_REG_CENTURY, bin2bcd(dt->tm_year / 100)); |
103 | |
104 | /* Compulab used a delay here. However, the datasheet |
105 | * does not mention a delay being required anywhere... */ |
106 | /* delay(2000); */ |
107 | |
108 | /* Write protect */ |
109 | max6902_set_reg(dev, MAX6902_REG_CONTROL, data: 0x80); |
110 | |
111 | return 0; |
112 | } |
113 | |
114 | static const struct rtc_class_ops max6902_rtc_ops = { |
115 | .read_time = max6902_read_time, |
116 | .set_time = max6902_set_time, |
117 | }; |
118 | |
119 | static int max6902_probe(struct spi_device *spi) |
120 | { |
121 | struct rtc_device *rtc; |
122 | unsigned char tmp; |
123 | int res; |
124 | |
125 | spi->mode = SPI_MODE_3; |
126 | spi->bits_per_word = 8; |
127 | spi_setup(spi); |
128 | |
129 | res = max6902_get_reg(dev: &spi->dev, MAX6902_REG_SECONDS, data: &tmp); |
130 | if (res != 0) |
131 | return res; |
132 | |
133 | rtc = devm_rtc_device_register(dev: &spi->dev, name: "max6902" , |
134 | ops: &max6902_rtc_ops, THIS_MODULE); |
135 | if (IS_ERR(ptr: rtc)) |
136 | return PTR_ERR(ptr: rtc); |
137 | |
138 | spi_set_drvdata(spi, data: rtc); |
139 | return 0; |
140 | } |
141 | |
142 | static struct spi_driver max6902_driver = { |
143 | .driver = { |
144 | .name = "rtc-max6902" , |
145 | }, |
146 | .probe = max6902_probe, |
147 | }; |
148 | |
149 | module_spi_driver(max6902_driver); |
150 | |
151 | MODULE_DESCRIPTION("max6902 spi RTC driver" ); |
152 | MODULE_AUTHOR("Raphael Assenat" ); |
153 | MODULE_LICENSE("GPL" ); |
154 | MODULE_ALIAS("spi:rtc-max6902" ); |
155 | |