1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * An rtc driver for the Dallas DS1742
4 *
5 * Copyright (C) 2006 Atsushi Nemoto <anemo@mba.ocn.ne.jp>
6 *
7 * Copyright (C) 2006 Torsten Ertbjerg Rasmussen <tr@newtec.dk>
8 *  - nvram size determined from resource
9 *  - this ds1742 driver now supports ds1743.
10 */
11
12#include <linux/bcd.h>
13#include <linux/kernel.h>
14#include <linux/gfp.h>
15#include <linux/delay.h>
16#include <linux/jiffies.h>
17#include <linux/rtc.h>
18#include <linux/of.h>
19#include <linux/platform_device.h>
20#include <linux/io.h>
21#include <linux/module.h>
22
23#define RTC_SIZE		8
24
25#define RTC_CONTROL		0
26#define RTC_CENTURY		0
27#define RTC_SECONDS		1
28#define RTC_MINUTES		2
29#define RTC_HOURS		3
30#define RTC_DAY			4
31#define RTC_DATE		5
32#define RTC_MONTH		6
33#define RTC_YEAR		7
34
35#define RTC_CENTURY_MASK	0x3f
36#define RTC_SECONDS_MASK	0x7f
37#define RTC_DAY_MASK		0x07
38
39/* Bits in the Control/Century register */
40#define RTC_WRITE		0x80
41#define RTC_READ		0x40
42
43/* Bits in the Seconds register */
44#define RTC_STOP		0x80
45
46/* Bits in the Day register */
47#define RTC_BATT_FLAG		0x80
48
49struct rtc_plat_data {
50	void __iomem *ioaddr_nvram;
51	void __iomem *ioaddr_rtc;
52	unsigned long last_jiffies;
53};
54
55static int ds1742_rtc_set_time(struct device *dev, struct rtc_time *tm)
56{
57	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
58	void __iomem *ioaddr = pdata->ioaddr_rtc;
59	u8 century;
60
61	century = bin2bcd((tm->tm_year + 1900) / 100);
62
63	writeb(RTC_WRITE, ioaddr + RTC_CONTROL);
64
65	writeb(bin2bcd(tm->tm_year % 100), ioaddr + RTC_YEAR);
66	writeb(bin2bcd(tm->tm_mon + 1), ioaddr + RTC_MONTH);
67	writeb(bin2bcd(tm->tm_wday) & RTC_DAY_MASK, ioaddr + RTC_DAY);
68	writeb(bin2bcd(tm->tm_mday), ioaddr + RTC_DATE);
69	writeb(bin2bcd(tm->tm_hour), ioaddr + RTC_HOURS);
70	writeb(bin2bcd(tm->tm_min), ioaddr + RTC_MINUTES);
71	writeb(bin2bcd(tm->tm_sec) & RTC_SECONDS_MASK, ioaddr + RTC_SECONDS);
72
73	/* RTC_CENTURY and RTC_CONTROL share same register */
74	writeb(RTC_WRITE | (century & RTC_CENTURY_MASK), ioaddr + RTC_CENTURY);
75	writeb(century & RTC_CENTURY_MASK, ioaddr + RTC_CONTROL);
76	return 0;
77}
78
79static int ds1742_rtc_read_time(struct device *dev, struct rtc_time *tm)
80{
81	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
82	void __iomem *ioaddr = pdata->ioaddr_rtc;
83	unsigned int year, month, day, hour, minute, second, week;
84	unsigned int century;
85
86	/* give enough time to update RTC in case of continuous read */
87	if (pdata->last_jiffies == jiffies)
88		msleep(1);
89	pdata->last_jiffies = jiffies;
90	writeb(RTC_READ, ioaddr + RTC_CONTROL);
91	second = readb(ioaddr + RTC_SECONDS) & RTC_SECONDS_MASK;
92	minute = readb(ioaddr + RTC_MINUTES);
93	hour = readb(ioaddr + RTC_HOURS);
94	day = readb(ioaddr + RTC_DATE);
95	week = readb(ioaddr + RTC_DAY) & RTC_DAY_MASK;
96	month = readb(ioaddr + RTC_MONTH);
97	year = readb(ioaddr + RTC_YEAR);
98	century = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
99	writeb(0, ioaddr + RTC_CONTROL);
100	tm->tm_sec = bcd2bin(second);
101	tm->tm_min = bcd2bin(minute);
102	tm->tm_hour = bcd2bin(hour);
103	tm->tm_mday = bcd2bin(day);
104	tm->tm_wday = bcd2bin(week);
105	tm->tm_mon = bcd2bin(month) - 1;
106	/* year is 1900 + tm->tm_year */
107	tm->tm_year = bcd2bin(year) + bcd2bin(century) * 100 - 1900;
108
109	return 0;
110}
111
112static const struct rtc_class_ops ds1742_rtc_ops = {
113	.read_time	= ds1742_rtc_read_time,
114	.set_time	= ds1742_rtc_set_time,
115};
116
117static int ds1742_nvram_read(void *priv, unsigned int pos, void *val,
118			     size_t bytes)
119{
120	struct rtc_plat_data *pdata = priv;
121	void __iomem *ioaddr = pdata->ioaddr_nvram;
122	u8 *buf = val;
123
124	for (; bytes; bytes--)
125		*buf++ = readb(ioaddr + pos++);
126	return 0;
127}
128
129static int ds1742_nvram_write(void *priv, unsigned int pos, void *val,
130			      size_t bytes)
131{
132	struct rtc_plat_data *pdata = priv;
133	void __iomem *ioaddr = pdata->ioaddr_nvram;
134	u8 *buf = val;
135
136	for (; bytes; bytes--)
137		writeb(*buf++, ioaddr + pos++);
138	return 0;
139}
140
141static int ds1742_rtc_probe(struct platform_device *pdev)
142{
143	struct rtc_device *rtc;
144	struct resource *res;
145	unsigned int cen, sec;
146	struct rtc_plat_data *pdata;
147	void __iomem *ioaddr;
148	int ret = 0;
149	struct nvmem_config nvmem_cfg = {
150		.name = "ds1742_nvram",
151		.reg_read = ds1742_nvram_read,
152		.reg_write = ds1742_nvram_write,
153	};
154
155
156	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
157	if (!pdata)
158		return -ENOMEM;
159
160	ioaddr = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
161	if (IS_ERR(ioaddr))
162		return PTR_ERR(ioaddr);
163
164	pdata->ioaddr_nvram = ioaddr;
165	pdata->ioaddr_rtc = ioaddr + resource_size(res) - RTC_SIZE;
166
167	nvmem_cfg.size = resource_size(res) - RTC_SIZE;
168	nvmem_cfg.priv = pdata;
169
170	/* turn RTC on if it was not on */
171	ioaddr = pdata->ioaddr_rtc;
172	sec = readb(ioaddr + RTC_SECONDS);
173	if (sec & RTC_STOP) {
174		sec &= RTC_SECONDS_MASK;
175		cen = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
176		writeb(RTC_WRITE, ioaddr + RTC_CONTROL);
177		writeb(sec, ioaddr + RTC_SECONDS);
178		writeb(cen & RTC_CENTURY_MASK, ioaddr + RTC_CONTROL);
179	}
180	if (!(readb(ioaddr + RTC_DAY) & RTC_BATT_FLAG))
181		dev_warn(&pdev->dev, "voltage-low detected.\n");
182
183	pdata->last_jiffies = jiffies;
184	platform_set_drvdata(pdev, pdata);
185
186	rtc = devm_rtc_allocate_device(&pdev->dev);
187	if (IS_ERR(rtc))
188		return PTR_ERR(rtc);
189
190	rtc->ops = &ds1742_rtc_ops;
191
192	ret = devm_rtc_register_device(rtc);
193	if (ret)
194		return ret;
195
196	devm_rtc_nvmem_register(rtc, &nvmem_cfg);
197
198	return 0;
199}
200
201static const struct of_device_id __maybe_unused ds1742_rtc_of_match[] = {
202	{ .compatible = "maxim,ds1742", },
203	{ }
204};
205MODULE_DEVICE_TABLE(of, ds1742_rtc_of_match);
206
207static struct platform_driver ds1742_rtc_driver = {
208	.probe		= ds1742_rtc_probe,
209	.driver		= {
210		.name	= "rtc-ds1742",
211		.of_match_table = of_match_ptr(ds1742_rtc_of_match),
212	},
213};
214
215module_platform_driver(ds1742_rtc_driver);
216
217MODULE_AUTHOR("Atsushi Nemoto <anemo@mba.ocn.ne.jp>");
218MODULE_DESCRIPTION("Dallas DS1742 RTC driver");
219MODULE_LICENSE("GPL");
220MODULE_ALIAS("platform:rtc-ds1742");
221