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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
15struct 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
29struct ds1216_priv {
30 struct rtc_device *rtc;
31 void __iomem *ioaddr;
32};
33
34static 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 */
43static 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
56static 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
70static 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
78static 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
105static 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
133static const struct rtc_class_ops ds1216_rtc_ops = {
134 .read_time = ds1216_rtc_read_time,
135 .set_time = ds1216_rtc_set_time,
136};
137
138static 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
163static struct platform_driver ds1216_rtc_platform_driver = {
164 .driver = {
165 .name = "rtc-ds1216",
166 },
167};
168
169module_platform_driver_probe(ds1216_rtc_platform_driver, ds1216_rtc_probe);
170
171MODULE_AUTHOR("Thomas Bogendoerfer <[email protected]>");
172MODULE_DESCRIPTION("DS1216 RTC driver");
173MODULE_LICENSE("GPL");
174MODULE_ALIAS("platform:rtc-ds1216");