1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * rtc-ds1390.c -- driver for the Dallas/Maxim DS1390/93/94 SPI RTC
4 *
5 * Copyright (C) 2008 Mercury IMC Ltd
6 * Written by Mark Jackson <mpfj@mimc.co.uk>
7 *
8 * NOTE: Currently this driver only supports the bare minimum for read
9 * and write the RTC. The extra features provided by the chip family
10 * (alarms, trickle charger, different control registers) are unavailable.
11 */
12
13#include <linux/init.h>
14#include <linux/module.h>
15#include <linux/platform_device.h>
16#include <linux/rtc.h>
17#include <linux/spi/spi.h>
18#include <linux/bcd.h>
19#include <linux/slab.h>
20#include <linux/of.h>
21
22#define DS1390_REG_100THS		0x00
23#define DS1390_REG_SECONDS		0x01
24#define DS1390_REG_MINUTES		0x02
25#define DS1390_REG_HOURS		0x03
26#define DS1390_REG_DAY			0x04
27#define DS1390_REG_DATE			0x05
28#define DS1390_REG_MONTH_CENT		0x06
29#define DS1390_REG_YEAR			0x07
30
31#define DS1390_REG_ALARM_100THS		0x08
32#define DS1390_REG_ALARM_SECONDS	0x09
33#define DS1390_REG_ALARM_MINUTES	0x0A
34#define DS1390_REG_ALARM_HOURS		0x0B
35#define DS1390_REG_ALARM_DAY_DATE	0x0C
36
37#define DS1390_REG_CONTROL		0x0D
38#define DS1390_REG_STATUS		0x0E
39#define DS1390_REG_TRICKLE		0x0F
40
41#define DS1390_TRICKLE_CHARGER_ENABLE	0xA0
42#define DS1390_TRICKLE_CHARGER_250_OHM	0x01
43#define DS1390_TRICKLE_CHARGER_2K_OHM	0x02
44#define DS1390_TRICKLE_CHARGER_4K_OHM	0x03
45#define DS1390_TRICKLE_CHARGER_NO_DIODE	0x04
46#define DS1390_TRICKLE_CHARGER_DIODE	0x08
47
48struct ds1390 {
49	struct rtc_device *rtc;
50	u8 txrx_buf[9];	/* cmd + 8 registers */
51};
52
53static void ds1390_set_reg(struct device *dev, unsigned char address,
54			   unsigned char data)
55{
56	struct spi_device *spi = to_spi_device(dev);
57	unsigned char buf[2];
58
59	/* MSB must be '1' to write */
60	buf[0] = address | 0x80;
61	buf[1] = data;
62
63	spi_write(spi, buf, 2);
64}
65
66static int ds1390_get_reg(struct device *dev, unsigned char address,
67				unsigned char *data)
68{
69	struct spi_device *spi = to_spi_device(dev);
70	struct ds1390 *chip = dev_get_drvdata(dev);
71	int status;
72
73	if (!data)
74		return -EINVAL;
75
76	/* Clear MSB to indicate read */
77	chip->txrx_buf[0] = address & 0x7f;
78	/* do the i/o */
79	status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 1);
80	if (status != 0)
81		return status;
82
83	*data = chip->txrx_buf[0];
84
85	return 0;
86}
87
88static void ds1390_trickle_of_init(struct spi_device *spi)
89{
90	u32 ohms = 0;
91	u8 value;
92
93	if (of_property_read_u32(spi->dev.of_node, "trickle-resistor-ohms",
94				 &ohms))
95		goto out;
96
97	/* Enable charger */
98	value = DS1390_TRICKLE_CHARGER_ENABLE;
99	if (of_property_read_bool(spi->dev.of_node, "trickle-diode-disable"))
100		value |= DS1390_TRICKLE_CHARGER_NO_DIODE;
101	else
102		value |= DS1390_TRICKLE_CHARGER_DIODE;
103
104	/* Resistor select */
105	switch (ohms) {
106	case 250:
107		value |= DS1390_TRICKLE_CHARGER_250_OHM;
108		break;
109	case 2000:
110		value |= DS1390_TRICKLE_CHARGER_2K_OHM;
111		break;
112	case 4000:
113		value |= DS1390_TRICKLE_CHARGER_4K_OHM;
114		break;
115	default:
116		dev_warn(&spi->dev,
117			 "Unsupported ohm value %02ux in dt\n", ohms);
118		return;
119	}
120
121	ds1390_set_reg(&spi->dev, DS1390_REG_TRICKLE, value);
122
123out:
124	return;
125}
126
127static int ds1390_read_time(struct device *dev, struct rtc_time *dt)
128{
129	struct spi_device *spi = to_spi_device(dev);
130	struct ds1390 *chip = dev_get_drvdata(dev);
131	int status;
132
133	/* build the message */
134	chip->txrx_buf[0] = DS1390_REG_SECONDS;
135
136	/* do the i/o */
137	status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 8);
138	if (status != 0)
139		return status;
140
141	/* The chip sends data in this order:
142	 * Seconds, Minutes, Hours, Day, Date, Month / Century, Year */
143	dt->tm_sec	= bcd2bin(chip->txrx_buf[0]);
144	dt->tm_min	= bcd2bin(chip->txrx_buf[1]);
145	dt->tm_hour	= bcd2bin(chip->txrx_buf[2]);
146	dt->tm_wday	= bcd2bin(chip->txrx_buf[3]);
147	dt->tm_mday	= bcd2bin(chip->txrx_buf[4]);
148	/* mask off century bit */
149	dt->tm_mon	= bcd2bin(chip->txrx_buf[5] & 0x7f) - 1;
150	/* adjust for century bit */
151	dt->tm_year = bcd2bin(chip->txrx_buf[6]) + ((chip->txrx_buf[5] & 0x80) ? 100 : 0);
152
153	return 0;
154}
155
156static int ds1390_set_time(struct device *dev, struct rtc_time *dt)
157{
158	struct spi_device *spi = to_spi_device(dev);
159	struct ds1390 *chip = dev_get_drvdata(dev);
160
161	/* build the message */
162	chip->txrx_buf[0] = DS1390_REG_SECONDS | 0x80;
163	chip->txrx_buf[1] = bin2bcd(dt->tm_sec);
164	chip->txrx_buf[2] = bin2bcd(dt->tm_min);
165	chip->txrx_buf[3] = bin2bcd(dt->tm_hour);
166	chip->txrx_buf[4] = bin2bcd(dt->tm_wday);
167	chip->txrx_buf[5] = bin2bcd(dt->tm_mday);
168	chip->txrx_buf[6] = bin2bcd(dt->tm_mon + 1) |
169				((dt->tm_year > 99) ? 0x80 : 0x00);
170	chip->txrx_buf[7] = bin2bcd(dt->tm_year % 100);
171
172	/* do the i/o */
173	return spi_write_then_read(spi, chip->txrx_buf, 8, NULL, 0);
174}
175
176static const struct rtc_class_ops ds1390_rtc_ops = {
177	.read_time	= ds1390_read_time,
178	.set_time	= ds1390_set_time,
179};
180
181static int ds1390_probe(struct spi_device *spi)
182{
183	unsigned char tmp;
184	struct ds1390 *chip;
185	int res;
186
187	spi->mode = SPI_MODE_3;
188	spi->bits_per_word = 8;
189	spi_setup(spi);
190
191	chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL);
192	if (!chip)
193		return -ENOMEM;
194
195	spi_set_drvdata(spi, chip);
196
197	res = ds1390_get_reg(&spi->dev, DS1390_REG_SECONDS, &tmp);
198	if (res != 0) {
199		dev_err(&spi->dev, "unable to read device\n");
200		return res;
201	}
202
203	if (spi->dev.of_node)
204		ds1390_trickle_of_init(spi);
205
206	chip->rtc = devm_rtc_device_register(&spi->dev, "ds1390",
207					&ds1390_rtc_ops, THIS_MODULE);
208	if (IS_ERR(chip->rtc)) {
209		dev_err(&spi->dev, "unable to register device\n");
210		res = PTR_ERR(chip->rtc);
211	}
212
213	return res;
214}
215
216static const struct of_device_id ds1390_of_match[] __maybe_unused = {
217	{ .compatible = "dallas,ds1390" },
218	{}
219};
220MODULE_DEVICE_TABLE(of, ds1390_of_match);
221
222static const struct spi_device_id ds1390_spi_ids[] = {
223	{ .name = "ds1390" },
224	{}
225};
226MODULE_DEVICE_TABLE(spi, ds1390_spi_ids);
227
228static struct spi_driver ds1390_driver = {
229	.driver = {
230		.name	= "rtc-ds1390",
231		.of_match_table = of_match_ptr(ds1390_of_match),
232	},
233	.probe	= ds1390_probe,
234	.id_table = ds1390_spi_ids,
235};
236
237module_spi_driver(ds1390_driver);
238
239MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver");
240MODULE_AUTHOR("Mark Jackson <mpfj@mimc.co.uk>");
241MODULE_LICENSE("GPL");
242MODULE_ALIAS("spi:rtc-ds1390");
243