1/*
2 * rtc-ds1390.c -- driver for the Dallas/Maxim DS1390/93/94 SPI RTC
3 *
4 * Copyright (C) 2008 Mercury IMC Ltd
5 * Written by Mark Jackson <mpfj@mimc.co.uk>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * NOTE: Currently this driver only supports the bare minimum for read
12 * and write the RTC. The extra features provided by the chip family
13 * (alarms, trickle charger, different control registers) are unavailable.
14 */
15
16#include <linux/init.h>
17#include <linux/module.h>
18#include <linux/platform_device.h>
19#include <linux/rtc.h>
20#include <linux/spi/spi.h>
21#include <linux/bcd.h>
22#include <linux/slab.h>
23
24#define DS1390_REG_100THS		0x00
25#define DS1390_REG_SECONDS		0x01
26#define DS1390_REG_MINUTES		0x02
27#define DS1390_REG_HOURS		0x03
28#define DS1390_REG_DAY			0x04
29#define DS1390_REG_DATE			0x05
30#define DS1390_REG_MONTH_CENT		0x06
31#define DS1390_REG_YEAR			0x07
32
33#define DS1390_REG_ALARM_100THS		0x08
34#define DS1390_REG_ALARM_SECONDS	0x09
35#define DS1390_REG_ALARM_MINUTES	0x0A
36#define DS1390_REG_ALARM_HOURS		0x0B
37#define DS1390_REG_ALARM_DAY_DATE	0x0C
38
39#define DS1390_REG_CONTROL		0x0D
40#define DS1390_REG_STATUS		0x0E
41#define DS1390_REG_TRICKLE		0x0F
42
43struct ds1390 {
44	struct rtc_device *rtc;
45	u8 txrx_buf[9];	/* cmd + 8 registers */
46};
47
48static int ds1390_get_reg(struct device *dev, unsigned char address,
49				unsigned char *data)
50{
51	struct spi_device *spi = to_spi_device(dev);
52	struct ds1390 *chip = dev_get_drvdata(dev);
53	int status;
54
55	if (!data)
56		return -EINVAL;
57
58	/* Clear MSB to indicate read */
59	chip->txrx_buf[0] = address & 0x7f;
60	/* do the i/o */
61	status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 1);
62	if (status != 0)
63		return status;
64
65	*data = chip->txrx_buf[1];
66
67	return 0;
68}
69
70static int ds1390_read_time(struct device *dev, struct rtc_time *dt)
71{
72	struct spi_device *spi = to_spi_device(dev);
73	struct ds1390 *chip = dev_get_drvdata(dev);
74	int status;
75
76	/* build the message */
77	chip->txrx_buf[0] = DS1390_REG_SECONDS;
78
79	/* do the i/o */
80	status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 8);
81	if (status != 0)
82		return status;
83
84	/* The chip sends data in this order:
85	 * Seconds, Minutes, Hours, Day, Date, Month / Century, Year */
86	dt->tm_sec	= bcd2bin(chip->txrx_buf[0]);
87	dt->tm_min	= bcd2bin(chip->txrx_buf[1]);
88	dt->tm_hour	= bcd2bin(chip->txrx_buf[2]);
89	dt->tm_wday	= bcd2bin(chip->txrx_buf[3]);
90	dt->tm_mday	= bcd2bin(chip->txrx_buf[4]);
91	/* mask off century bit */
92	dt->tm_mon	= bcd2bin(chip->txrx_buf[5] & 0x7f) - 1;
93	/* adjust for century bit */
94	dt->tm_year = bcd2bin(chip->txrx_buf[6]) + ((chip->txrx_buf[5] & 0x80) ? 100 : 0);
95
96	return rtc_valid_tm(dt);
97}
98
99static int ds1390_set_time(struct device *dev, struct rtc_time *dt)
100{
101	struct spi_device *spi = to_spi_device(dev);
102	struct ds1390 *chip = dev_get_drvdata(dev);
103
104	/* build the message */
105	chip->txrx_buf[0] = DS1390_REG_SECONDS | 0x80;
106	chip->txrx_buf[1] = bin2bcd(dt->tm_sec);
107	chip->txrx_buf[2] = bin2bcd(dt->tm_min);
108	chip->txrx_buf[3] = bin2bcd(dt->tm_hour);
109	chip->txrx_buf[4] = bin2bcd(dt->tm_wday);
110	chip->txrx_buf[5] = bin2bcd(dt->tm_mday);
111	chip->txrx_buf[6] = bin2bcd(dt->tm_mon + 1) |
112				((dt->tm_year > 99) ? 0x80 : 0x00);
113	chip->txrx_buf[7] = bin2bcd(dt->tm_year % 100);
114
115	/* do the i/o */
116	return spi_write_then_read(spi, chip->txrx_buf, 8, NULL, 0);
117}
118
119static const struct rtc_class_ops ds1390_rtc_ops = {
120	.read_time	= ds1390_read_time,
121	.set_time	= ds1390_set_time,
122};
123
124static int ds1390_probe(struct spi_device *spi)
125{
126	unsigned char tmp;
127	struct ds1390 *chip;
128	int res;
129
130	spi->mode = SPI_MODE_3;
131	spi->bits_per_word = 8;
132	spi_setup(spi);
133
134	chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL);
135	if (!chip)
136		return -ENOMEM;
137
138	spi_set_drvdata(spi, chip);
139
140	res = ds1390_get_reg(&spi->dev, DS1390_REG_SECONDS, &tmp);
141	if (res != 0) {
142		dev_err(&spi->dev, "unable to read device\n");
143		return res;
144	}
145
146	chip->rtc = devm_rtc_device_register(&spi->dev, "ds1390",
147					&ds1390_rtc_ops, THIS_MODULE);
148	if (IS_ERR(chip->rtc)) {
149		dev_err(&spi->dev, "unable to register device\n");
150		res = PTR_ERR(chip->rtc);
151	}
152
153	return res;
154}
155
156static struct spi_driver ds1390_driver = {
157	.driver = {
158		.name	= "rtc-ds1390",
159		.owner	= THIS_MODULE,
160	},
161	.probe	= ds1390_probe,
162};
163
164module_spi_driver(ds1390_driver);
165
166MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver");
167MODULE_AUTHOR("Mark Jackson <mpfj@mimc.co.uk>");
168MODULE_LICENSE("GPL");
169MODULE_ALIAS("spi:rtc-ds1390");
170