xref: /linux/drivers/rtc/rtc-ds1216.c (revision 24168c5e6dfbdd5b414f048f47f75d64533296ca)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Dallas DS1216 RTC driver
4  *
5  * Copyright (c) 2007 Thomas Bogendoerfer
6  *
7  */
8 
9 #include <linux/module.h>
10 #include <linux/rtc.h>
11 #include <linux/platform_device.h>
12 #include <linux/bcd.h>
13 #include <linux/slab.h>
14 
15 struct ds1216_regs {
16 	u8 tsec;
17 	u8 sec;
18 	u8 min;
19 	u8 hour;
20 	u8 wday;
21 	u8 mday;
22 	u8 month;
23 	u8 year;
24 };
25 
26 #define DS1216_HOUR_1224	(1 << 7)
27 #define DS1216_HOUR_AMPM	(1 << 5)
28 
29 struct ds1216_priv {
30 	struct rtc_device *rtc;
31 	void __iomem *ioaddr;
32 };
33 
34 static const u8 magic[] = {
35 	0xc5, 0x3a, 0xa3, 0x5c, 0xc5, 0x3a, 0xa3, 0x5c
36 };
37 
38 /*
39  * Read the 64 bit we'd like to have - It a series
40  * of 64 bits showing up in the LSB of the base register.
41  *
42  */
43 static void ds1216_read(u8 __iomem *ioaddr, u8 *buf)
44 {
45 	unsigned char c;
46 	int i, j;
47 
48 	for (i = 0; i < 8; i++) {
49 		c = 0;
50 		for (j = 0; j < 8; j++)
51 			c |= (readb(ioaddr) & 0x1) << j;
52 		buf[i] = c;
53 	}
54 }
55 
56 static void ds1216_write(u8 __iomem *ioaddr, const u8 *buf)
57 {
58 	unsigned char c;
59 	int i, j;
60 
61 	for (i = 0; i < 8; i++) {
62 		c = buf[i];
63 		for (j = 0; j < 8; j++) {
64 			writeb(c, ioaddr);
65 			c = c >> 1;
66 		}
67 	}
68 }
69 
70 static void ds1216_switch_ds_to_clock(u8 __iomem *ioaddr)
71 {
72 	/* Reset magic pointer */
73 	readb(ioaddr);
74 	/* Write 64 bit magic to DS1216 */
75 	ds1216_write(ioaddr, magic);
76 }
77 
78 static int ds1216_rtc_read_time(struct device *dev, struct rtc_time *tm)
79 {
80 	struct ds1216_priv *priv = dev_get_drvdata(dev);
81 	struct ds1216_regs regs;
82 
83 	ds1216_switch_ds_to_clock(priv->ioaddr);
84 	ds1216_read(priv->ioaddr, (u8 *)&regs);
85 
86 	tm->tm_sec = bcd2bin(regs.sec);
87 	tm->tm_min = bcd2bin(regs.min);
88 	if (regs.hour & DS1216_HOUR_1224) {
89 		/* AM/PM mode */
90 		tm->tm_hour = bcd2bin(regs.hour & 0x1f);
91 		if (regs.hour & DS1216_HOUR_AMPM)
92 			tm->tm_hour += 12;
93 	} else
94 		tm->tm_hour = bcd2bin(regs.hour & 0x3f);
95 	tm->tm_wday = (regs.wday & 7) - 1;
96 	tm->tm_mday = bcd2bin(regs.mday & 0x3f);
97 	tm->tm_mon = bcd2bin(regs.month & 0x1f);
98 	tm->tm_year = bcd2bin(regs.year);
99 	if (tm->tm_year < 70)
100 		tm->tm_year += 100;
101 
102 	return 0;
103 }
104 
105 static int ds1216_rtc_set_time(struct device *dev, struct rtc_time *tm)
106 {
107 	struct ds1216_priv *priv = dev_get_drvdata(dev);
108 	struct ds1216_regs regs;
109 
110 	ds1216_switch_ds_to_clock(priv->ioaddr);
111 	ds1216_read(priv->ioaddr, (u8 *)&regs);
112 
113 	regs.tsec = 0; /* clear 0.1 and 0.01 seconds */
114 	regs.sec = bin2bcd(tm->tm_sec);
115 	regs.min = bin2bcd(tm->tm_min);
116 	regs.hour &= DS1216_HOUR_1224;
117 	if (regs.hour && tm->tm_hour > 12) {
118 		regs.hour |= DS1216_HOUR_AMPM;
119 		tm->tm_hour -= 12;
120 	}
121 	regs.hour |= bin2bcd(tm->tm_hour);
122 	regs.wday &= ~7;
123 	regs.wday |= tm->tm_wday;
124 	regs.mday = bin2bcd(tm->tm_mday);
125 	regs.month = bin2bcd(tm->tm_mon);
126 	regs.year = bin2bcd(tm->tm_year % 100);
127 
128 	ds1216_switch_ds_to_clock(priv->ioaddr);
129 	ds1216_write(priv->ioaddr, (u8 *)&regs);
130 	return 0;
131 }
132 
133 static const struct rtc_class_ops ds1216_rtc_ops = {
134 	.read_time	= ds1216_rtc_read_time,
135 	.set_time	= ds1216_rtc_set_time,
136 };
137 
138 static int __init ds1216_rtc_probe(struct platform_device *pdev)
139 {
140 	struct ds1216_priv *priv;
141 	u8 dummy[8];
142 
143 	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
144 	if (!priv)
145 		return -ENOMEM;
146 
147 	platform_set_drvdata(pdev, priv);
148 
149 	priv->ioaddr = devm_platform_ioremap_resource(pdev, 0);
150 	if (IS_ERR(priv->ioaddr))
151 		return PTR_ERR(priv->ioaddr);
152 
153 	priv->rtc = devm_rtc_device_register(&pdev->dev, "ds1216",
154 					&ds1216_rtc_ops, THIS_MODULE);
155 	if (IS_ERR(priv->rtc))
156 		return PTR_ERR(priv->rtc);
157 
158 	/* dummy read to get clock into a known state */
159 	ds1216_read(priv->ioaddr, dummy);
160 	return 0;
161 }
162 
163 static struct platform_driver ds1216_rtc_platform_driver = {
164 	.driver		= {
165 		.name	= "rtc-ds1216",
166 	},
167 };
168 
169 module_platform_driver_probe(ds1216_rtc_platform_driver, ds1216_rtc_probe);
170 
171 MODULE_AUTHOR("Thomas Bogendoerfer <tsbogend@alpha.franken.de>");
172 MODULE_DESCRIPTION("DS1216 RTC driver");
173 MODULE_LICENSE("GPL");
174 MODULE_ALIAS("platform:rtc-ds1216");
175