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 #include <linux/of.h>
24 
25 #define DS1390_REG_100THS		0x00
26 #define DS1390_REG_SECONDS		0x01
27 #define DS1390_REG_MINUTES		0x02
28 #define DS1390_REG_HOURS		0x03
29 #define DS1390_REG_DAY			0x04
30 #define DS1390_REG_DATE			0x05
31 #define DS1390_REG_MONTH_CENT		0x06
32 #define DS1390_REG_YEAR			0x07
33 
34 #define DS1390_REG_ALARM_100THS		0x08
35 #define DS1390_REG_ALARM_SECONDS	0x09
36 #define DS1390_REG_ALARM_MINUTES	0x0A
37 #define DS1390_REG_ALARM_HOURS		0x0B
38 #define DS1390_REG_ALARM_DAY_DATE	0x0C
39 
40 #define DS1390_REG_CONTROL		0x0D
41 #define DS1390_REG_STATUS		0x0E
42 #define DS1390_REG_TRICKLE		0x0F
43 
44 #define DS1390_TRICKLE_CHARGER_ENABLE	0xA0
45 #define DS1390_TRICKLE_CHARGER_250_OHM	0x01
46 #define DS1390_TRICKLE_CHARGER_2K_OHM	0x02
47 #define DS1390_TRICKLE_CHARGER_4K_OHM	0x03
48 #define DS1390_TRICKLE_CHARGER_NO_DIODE	0x04
49 #define DS1390_TRICKLE_CHARGER_DIODE	0x08
50 
51 struct ds1390 {
52 	struct rtc_device *rtc;
53 	u8 txrx_buf[9];	/* cmd + 8 registers */
54 };
55 
ds1390_set_reg(struct device * dev,unsigned char address,unsigned char data)56 static void ds1390_set_reg(struct device *dev, unsigned char address,
57 			   unsigned char data)
58 {
59 	struct spi_device *spi = to_spi_device(dev);
60 	unsigned char buf[2];
61 
62 	/* MSB must be '1' to write */
63 	buf[0] = address | 0x80;
64 	buf[1] = data;
65 
66 	spi_write(spi, buf, 2);
67 }
68 
ds1390_get_reg(struct device * dev,unsigned char address,unsigned char * data)69 static int ds1390_get_reg(struct device *dev, unsigned char address,
70 				unsigned char *data)
71 {
72 	struct spi_device *spi = to_spi_device(dev);
73 	struct ds1390 *chip = dev_get_drvdata(dev);
74 	int status;
75 
76 	if (!data)
77 		return -EINVAL;
78 
79 	/* Clear MSB to indicate read */
80 	chip->txrx_buf[0] = address & 0x7f;
81 	/* do the i/o */
82 	status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 1);
83 	if (status != 0)
84 		return status;
85 
86 	*data = chip->txrx_buf[0];
87 
88 	return 0;
89 }
90 
ds1390_trickle_of_init(struct spi_device * spi)91 static void ds1390_trickle_of_init(struct spi_device *spi)
92 {
93 	u32 ohms = 0;
94 	u8 value;
95 
96 	if (of_property_read_u32(spi->dev.of_node, "trickle-resistor-ohms",
97 				 &ohms))
98 		goto out;
99 
100 	/* Enable charger */
101 	value = DS1390_TRICKLE_CHARGER_ENABLE;
102 	if (of_property_read_bool(spi->dev.of_node, "trickle-diode-disable"))
103 		value |= DS1390_TRICKLE_CHARGER_NO_DIODE;
104 	else
105 		value |= DS1390_TRICKLE_CHARGER_DIODE;
106 
107 	/* Resistor select */
108 	switch (ohms) {
109 	case 250:
110 		value |= DS1390_TRICKLE_CHARGER_250_OHM;
111 		break;
112 	case 2000:
113 		value |= DS1390_TRICKLE_CHARGER_2K_OHM;
114 		break;
115 	case 4000:
116 		value |= DS1390_TRICKLE_CHARGER_4K_OHM;
117 		break;
118 	default:
119 		dev_warn(&spi->dev,
120 			 "Unsupported ohm value %02ux in dt\n", ohms);
121 		return;
122 	}
123 
124 	ds1390_set_reg(&spi->dev, DS1390_REG_TRICKLE, value);
125 
126 out:
127 	return;
128 }
129 
ds1390_read_time(struct device * dev,struct rtc_time * dt)130 static int ds1390_read_time(struct device *dev, struct rtc_time *dt)
131 {
132 	struct spi_device *spi = to_spi_device(dev);
133 	struct ds1390 *chip = dev_get_drvdata(dev);
134 	int status;
135 
136 	/* build the message */
137 	chip->txrx_buf[0] = DS1390_REG_SECONDS;
138 
139 	/* do the i/o */
140 	status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 8);
141 	if (status != 0)
142 		return status;
143 
144 	/* The chip sends data in this order:
145 	 * Seconds, Minutes, Hours, Day, Date, Month / Century, Year */
146 	dt->tm_sec	= bcd2bin(chip->txrx_buf[0]);
147 	dt->tm_min	= bcd2bin(chip->txrx_buf[1]);
148 	dt->tm_hour	= bcd2bin(chip->txrx_buf[2]);
149 	dt->tm_wday	= bcd2bin(chip->txrx_buf[3]);
150 	dt->tm_mday	= bcd2bin(chip->txrx_buf[4]);
151 	/* mask off century bit */
152 	dt->tm_mon	= bcd2bin(chip->txrx_buf[5] & 0x7f) - 1;
153 	/* adjust for century bit */
154 	dt->tm_year = bcd2bin(chip->txrx_buf[6]) + ((chip->txrx_buf[5] & 0x80) ? 100 : 0);
155 
156 	return 0;
157 }
158 
ds1390_set_time(struct device * dev,struct rtc_time * dt)159 static int ds1390_set_time(struct device *dev, struct rtc_time *dt)
160 {
161 	struct spi_device *spi = to_spi_device(dev);
162 	struct ds1390 *chip = dev_get_drvdata(dev);
163 
164 	/* build the message */
165 	chip->txrx_buf[0] = DS1390_REG_SECONDS | 0x80;
166 	chip->txrx_buf[1] = bin2bcd(dt->tm_sec);
167 	chip->txrx_buf[2] = bin2bcd(dt->tm_min);
168 	chip->txrx_buf[3] = bin2bcd(dt->tm_hour);
169 	chip->txrx_buf[4] = bin2bcd(dt->tm_wday);
170 	chip->txrx_buf[5] = bin2bcd(dt->tm_mday);
171 	chip->txrx_buf[6] = bin2bcd(dt->tm_mon + 1) |
172 				((dt->tm_year > 99) ? 0x80 : 0x00);
173 	chip->txrx_buf[7] = bin2bcd(dt->tm_year % 100);
174 
175 	/* do the i/o */
176 	return spi_write_then_read(spi, chip->txrx_buf, 8, NULL, 0);
177 }
178 
179 static const struct rtc_class_ops ds1390_rtc_ops = {
180 	.read_time	= ds1390_read_time,
181 	.set_time	= ds1390_set_time,
182 };
183 
ds1390_probe(struct spi_device * spi)184 static int ds1390_probe(struct spi_device *spi)
185 {
186 	unsigned char tmp;
187 	struct ds1390 *chip;
188 	int res;
189 
190 	spi->mode = SPI_MODE_3;
191 	spi->bits_per_word = 8;
192 	spi_setup(spi);
193 
194 	chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL);
195 	if (!chip)
196 		return -ENOMEM;
197 
198 	spi_set_drvdata(spi, chip);
199 
200 	res = ds1390_get_reg(&spi->dev, DS1390_REG_SECONDS, &tmp);
201 	if (res != 0) {
202 		dev_err(&spi->dev, "unable to read device\n");
203 		return res;
204 	}
205 
206 	if (spi->dev.of_node)
207 		ds1390_trickle_of_init(spi);
208 
209 	chip->rtc = devm_rtc_device_register(&spi->dev, "ds1390",
210 					&ds1390_rtc_ops, THIS_MODULE);
211 	if (IS_ERR(chip->rtc)) {
212 		dev_err(&spi->dev, "unable to register device\n");
213 		res = PTR_ERR(chip->rtc);
214 	}
215 
216 	return res;
217 }
218 
219 static const struct of_device_id ds1390_of_match[] = {
220 	{ .compatible = "dallas,ds1390" },
221 	{}
222 };
223 MODULE_DEVICE_TABLE(of, ds1390_of_match);
224 
225 static struct spi_driver ds1390_driver = {
226 	.driver = {
227 		.name	= "rtc-ds1390",
228 		.of_match_table = of_match_ptr(ds1390_of_match),
229 	},
230 	.probe	= ds1390_probe,
231 };
232 
233 module_spi_driver(ds1390_driver);
234 
235 MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver");
236 MODULE_AUTHOR("Mark Jackson <mpfj@mimc.co.uk>");
237 MODULE_LICENSE("GPL");
238 MODULE_ALIAS("spi:rtc-ds1390");
239