xref: /linux/drivers/rtc/rtc-m48t35.c (revision ead5d1f4d877e92c051e1a1ade623d0d30e71619)
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 
21 struct 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 
47 struct 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 
m48t35_read_time(struct device * dev,struct rtc_time * tm)55 static 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 
m48t35_set_time(struct device * dev,struct rtc_time * tm)97 static 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 
145 static const struct rtc_class_ops m48t35_ops = {
146 	.read_time	= m48t35_read_time,
147 	.set_time	= m48t35_set_time,
148 };
149 
m48t35_probe(struct platform_device * pdev)150 static 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 
181 static struct platform_driver m48t35_platform_driver = {
182 	.driver		= {
183 		.name	= "rtc-m48t35",
184 	},
185 	.probe		= m48t35_probe,
186 };
187 
188 module_platform_driver(m48t35_platform_driver);
189 
190 MODULE_AUTHOR("Thomas Bogendoerfer <tsbogend@alpha.franken.de>");
191 MODULE_DESCRIPTION("M48T35 RTC driver");
192 MODULE_LICENSE("GPL");
193 MODULE_ALIAS("platform:rtc-m48t35");
194