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
