1/*
2 * Driver for the SGS-Thomson M48T35 Timekeeper RAM chip
3 *
4 * Copyright (C) 2000 Silicon Graphics, Inc.
5 * Written by Ulf Carlsson (ulfc@engr.sgi.com)
6 *
7 * Copyright (C) 2008 Thomas Bogendoerfer
8 *
9 * Based on code written by Paul Gortmaker.
10 *
11 * This program is free software; you can redistribute it and/or modify it
12 * under the terms of the GNU General Public License as published by the
13 * Free Software Foundation; either version 2 of the License, or (at your
14 * option) any later version.
15 */
16
17#include <linux/module.h>
18#include <linux/rtc.h>
19#include <linux/slab.h>
20#include <linux/platform_device.h>
21#include <linux/bcd.h>
22#include <linux/io.h>
23#include <linux/err.h>
24
25#define DRV_VERSION		"1.0"
26
27struct m48t35_rtc {
28	u8	pad[0x7ff8];    /* starts at 0x7ff8 */
29	u8	control;
30	u8	sec;
31	u8	min;
32	u8	hour;
33	u8	day;
34	u8	date;
35	u8	month;
36	u8	year;
37};
38
39#define M48T35_RTC_SET		0x80
40#define M48T35_RTC_READ		0x40
41
42struct m48t35_priv {
43	struct rtc_device *rtc;
44	struct m48t35_rtc __iomem *reg;
45	size_t size;
46	unsigned long baseaddr;
47	spinlock_t lock;
48};
49
50static int m48t35_read_time(struct device *dev, struct rtc_time *tm)
51{
52	struct m48t35_priv *priv = dev_get_drvdata(dev);
53	u8 control;
54
55	/*
56	 * Only the values that we read from the RTC are set. We leave
57	 * tm_wday, tm_yday and tm_isdst untouched. Even though the
58	 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
59	 * by the RTC when initially set to a non-zero value.
60	 */
61	spin_lock_irq(&priv->lock);
62	control = readb(&priv->reg->control);
63	writeb(control | M48T35_RTC_READ, &priv->reg->control);
64	tm->tm_sec = readb(&priv->reg->sec);
65	tm->tm_min = readb(&priv->reg->min);
66	tm->tm_hour = readb(&priv->reg->hour);
67	tm->tm_mday = readb(&priv->reg->date);
68	tm->tm_mon = readb(&priv->reg->month);
69	tm->tm_year = readb(&priv->reg->year);
70	writeb(control, &priv->reg->control);
71	spin_unlock_irq(&priv->lock);
72
73	tm->tm_sec = bcd2bin(tm->tm_sec);
74	tm->tm_min = bcd2bin(tm->tm_min);
75	tm->tm_hour = bcd2bin(tm->tm_hour);
76	tm->tm_mday = bcd2bin(tm->tm_mday);
77	tm->tm_mon = bcd2bin(tm->tm_mon);
78	tm->tm_year = bcd2bin(tm->tm_year);
79
80	/*
81	 * Account for differences between how the RTC uses the values
82	 * and how they are defined in a struct rtc_time;
83	 */
84	tm->tm_year += 70;
85	if (tm->tm_year <= 69)
86		tm->tm_year += 100;
87
88	tm->tm_mon--;
89	return rtc_valid_tm(tm);
90}
91
92static int m48t35_set_time(struct device *dev, struct rtc_time *tm)
93{
94	struct m48t35_priv *priv = dev_get_drvdata(dev);
95	unsigned char mon, day, hrs, min, sec;
96	unsigned int yrs;
97	u8 control;
98
99	yrs = tm->tm_year + 1900;
100	mon = tm->tm_mon + 1;   /* tm_mon starts at zero */
101	day = tm->tm_mday;
102	hrs = tm->tm_hour;
103	min = tm->tm_min;
104	sec = tm->tm_sec;
105
106	if (yrs < 1970)
107		return -EINVAL;
108
109	yrs -= 1970;
110	if (yrs > 255)    /* They are unsigned */
111		return -EINVAL;
112
113	if (yrs > 169)
114		return -EINVAL;
115
116	if (yrs >= 100)
117		yrs -= 100;
118
119	sec = bin2bcd(sec);
120	min = bin2bcd(min);
121	hrs = bin2bcd(hrs);
122	day = bin2bcd(day);
123	mon = bin2bcd(mon);
124	yrs = bin2bcd(yrs);
125
126	spin_lock_irq(&priv->lock);
127	control = readb(&priv->reg->control);
128	writeb(control | M48T35_RTC_SET, &priv->reg->control);
129	writeb(yrs, &priv->reg->year);
130	writeb(mon, &priv->reg->month);
131	writeb(day, &priv->reg->date);
132	writeb(hrs, &priv->reg->hour);
133	writeb(min, &priv->reg->min);
134	writeb(sec, &priv->reg->sec);
135	writeb(control, &priv->reg->control);
136	spin_unlock_irq(&priv->lock);
137	return 0;
138}
139
140static const struct rtc_class_ops m48t35_ops = {
141	.read_time	= m48t35_read_time,
142	.set_time	= m48t35_set_time,
143};
144
145static int m48t35_probe(struct platform_device *pdev)
146{
147	struct resource *res;
148	struct m48t35_priv *priv;
149
150	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
151	if (!res)
152		return -ENODEV;
153	priv = devm_kzalloc(&pdev->dev, sizeof(struct m48t35_priv), GFP_KERNEL);
154	if (!priv)
155		return -ENOMEM;
156
157	priv->size = resource_size(res);
158	/*
159	 * kludge: remove the #ifndef after ioc3 resource
160	 * conflicts are resolved
161	 */
162#ifndef CONFIG_SGI_IP27
163	if (!devm_request_mem_region(&pdev->dev, res->start, priv->size,
164				     pdev->name))
165		return -EBUSY;
166#endif
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_VERSION(DRV_VERSION);
194MODULE_ALIAS("platform:rtc-m48t35");
195