1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Driver for the SGS-Thomson M48T35 Timekeeper RAM chip
4 *
5 * Copyright (C) 2000 Silicon Graphics, Inc.
6 * Written by Ulf Carlsson (ulfc@engr.sgi.com)
7 *
8 * Copyright (C) 2008 Thomas Bogendoerfer
9 *
10 * Based on code written by Paul Gortmaker.
11 */
12
13#include <linux/module.h>
14#include <linux/rtc.h>
15#include <linux/slab.h>
16#include <linux/platform_device.h>
17#include <linux/bcd.h>
18#include <linux/io.h>
19#include <linux/err.h>
20
21struct m48t35_rtc {
22	u8	pad[0x7ff8];    /* starts at 0x7ff8 */
23#ifdef CONFIG_SGI_IP27
24	u8	hour;
25	u8	min;
26	u8	sec;
27	u8	control;
28	u8	year;
29	u8	month;
30	u8	date;
31	u8	day;
32#else
33	u8	control;
34	u8	sec;
35	u8	min;
36	u8	hour;
37	u8	day;
38	u8	date;
39	u8	month;
40	u8	year;
41#endif
42};
43
44#define M48T35_RTC_SET		0x80
45#define M48T35_RTC_READ		0x40
46
47struct m48t35_priv {
48	struct rtc_device *rtc;
49	struct m48t35_rtc __iomem *reg;
50	size_t size;
51	unsigned long baseaddr;
52	spinlock_t lock;
53};
54
55static int m48t35_read_time(struct device *dev, struct rtc_time *tm)
56{
57	struct m48t35_priv *priv = dev_get_drvdata(dev);
58	u8 control;
59
60	/*
61	 * Only the values that we read from the RTC are set. We leave
62	 * tm_wday, tm_yday and tm_isdst untouched. Even though the
63	 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
64	 * by the RTC when initially set to a non-zero value.
65	 */
66	spin_lock_irq(&priv->lock);
67	control = readb(&priv->reg->control);
68	writeb(control | M48T35_RTC_READ, &priv->reg->control);
69	tm->tm_sec = readb(&priv->reg->sec);
70	tm->tm_min = readb(&priv->reg->min);
71	tm->tm_hour = readb(&priv->reg->hour);
72	tm->tm_mday = readb(&priv->reg->date);
73	tm->tm_mon = readb(&priv->reg->month);
74	tm->tm_year = readb(&priv->reg->year);
75	writeb(control, &priv->reg->control);
76	spin_unlock_irq(&priv->lock);
77
78	tm->tm_sec = bcd2bin(tm->tm_sec);
79	tm->tm_min = bcd2bin(tm->tm_min);
80	tm->tm_hour = bcd2bin(tm->tm_hour);
81	tm->tm_mday = bcd2bin(tm->tm_mday);
82	tm->tm_mon = bcd2bin(tm->tm_mon);
83	tm->tm_year = bcd2bin(tm->tm_year);
84
85	/*
86	 * Account for differences between how the RTC uses the values
87	 * and how they are defined in a struct rtc_time;
88	 */
89	tm->tm_year += 70;
90	if (tm->tm_year <= 69)
91		tm->tm_year += 100;
92
93	tm->tm_mon--;
94	return 0;
95}
96
97static int m48t35_set_time(struct device *dev, struct rtc_time *tm)
98{
99	struct m48t35_priv *priv = dev_get_drvdata(dev);
100	unsigned char mon, day, hrs, min, sec;
101	unsigned int yrs;
102	u8 control;
103
104	yrs = tm->tm_year + 1900;
105	mon = tm->tm_mon + 1;   /* tm_mon starts at zero */
106	day = tm->tm_mday;
107	hrs = tm->tm_hour;
108	min = tm->tm_min;
109	sec = tm->tm_sec;
110
111	if (yrs < 1970)
112		return -EINVAL;
113
114	yrs -= 1970;
115	if (yrs > 255)    /* They are unsigned */
116		return -EINVAL;
117
118	if (yrs > 169)
119		return -EINVAL;
120
121	if (yrs >= 100)
122		yrs -= 100;
123
124	sec = bin2bcd(sec);
125	min = bin2bcd(min);
126	hrs = bin2bcd(hrs);
127	day = bin2bcd(day);
128	mon = bin2bcd(mon);
129	yrs = bin2bcd(yrs);
130
131	spin_lock_irq(&priv->lock);
132	control = readb(&priv->reg->control);
133	writeb(control | M48T35_RTC_SET, &priv->reg->control);
134	writeb(yrs, &priv->reg->year);
135	writeb(mon, &priv->reg->month);
136	writeb(day, &priv->reg->date);
137	writeb(hrs, &priv->reg->hour);
138	writeb(min, &priv->reg->min);
139	writeb(sec, &priv->reg->sec);
140	writeb(control, &priv->reg->control);
141	spin_unlock_irq(&priv->lock);
142	return 0;
143}
144
145static const struct rtc_class_ops m48t35_ops = {
146	.read_time	= m48t35_read_time,
147	.set_time	= m48t35_set_time,
148};
149
150static int m48t35_probe(struct platform_device *pdev)
151{
152	struct resource *res;
153	struct m48t35_priv *priv;
154
155	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
156	if (!res)
157		return -ENODEV;
158	priv = devm_kzalloc(&pdev->dev, sizeof(struct m48t35_priv), GFP_KERNEL);
159	if (!priv)
160		return -ENOMEM;
161
162	priv->size = resource_size(res);
163	if (!devm_request_mem_region(&pdev->dev, res->start, priv->size,
164				     pdev->name))
165		return -EBUSY;
166
167	priv->baseaddr = res->start;
168	priv->reg = devm_ioremap(&pdev->dev, priv->baseaddr, priv->size);
169	if (!priv->reg)
170		return -ENOMEM;
171
172	spin_lock_init(&priv->lock);
173
174	platform_set_drvdata(pdev, priv);
175
176	priv->rtc = devm_rtc_device_register(&pdev->dev, "m48t35",
177				  &m48t35_ops, THIS_MODULE);
178	return PTR_ERR_OR_ZERO(priv->rtc);
179}
180
181static struct platform_driver m48t35_platform_driver = {
182	.driver		= {
183		.name	= "rtc-m48t35",
184	},
185	.probe		= m48t35_probe,
186};
187
188module_platform_driver(m48t35_platform_driver);
189
190MODULE_AUTHOR("Thomas Bogendoerfer <tsbogend@alpha.franken.de>");
191MODULE_DESCRIPTION("M48T35 RTC driver");
192MODULE_LICENSE("GPL");
193MODULE_ALIAS("platform:rtc-m48t35");
194