xref: /linux/drivers/rtc/rtc-m48t86.c (revision 03c11eb3b16dc0058589751dfd91f254be2be613)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * ST M48T86 / Dallas DS12887 RTC driver
4  * Copyright (c) 2006 Tower Technologies
5  *
6  * Author: Alessandro Zummo <a.zummo@towertech.it>
7  *
8  * This drivers only supports the clock running in BCD and 24H mode.
9  * If it will be ever adapted to binary and 12H mode, care must be taken
10  * to not introduce bugs.
11  */
12 
13 #include <linux/module.h>
14 #include <linux/mod_devicetable.h>
15 #include <linux/rtc.h>
16 #include <linux/platform_device.h>
17 #include <linux/bcd.h>
18 #include <linux/io.h>
19 
20 #define M48T86_SEC		0x00
21 #define M48T86_SECALRM		0x01
22 #define M48T86_MIN		0x02
23 #define M48T86_MINALRM		0x03
24 #define M48T86_HOUR		0x04
25 #define M48T86_HOURALRM		0x05
26 #define M48T86_DOW		0x06 /* 1 = sunday */
27 #define M48T86_DOM		0x07
28 #define M48T86_MONTH		0x08 /* 1 - 12 */
29 #define M48T86_YEAR		0x09 /* 0 - 99 */
30 #define M48T86_A		0x0a
31 #define M48T86_B		0x0b
32 #define M48T86_B_SET		BIT(7)
33 #define M48T86_B_DM		BIT(2)
34 #define M48T86_B_H24		BIT(1)
35 #define M48T86_C		0x0c
36 #define M48T86_D		0x0d
37 #define M48T86_D_VRT		BIT(7)
38 #define M48T86_NVRAM(x)		(0x0e + (x))
39 #define M48T86_NVRAM_LEN	114
40 
41 struct m48t86_rtc_info {
42 	void __iomem *index_reg;
43 	void __iomem *data_reg;
44 	struct rtc_device *rtc;
45 };
46 
m48t86_readb(struct device * dev,unsigned long addr)47 static unsigned char m48t86_readb(struct device *dev, unsigned long addr)
48 {
49 	struct m48t86_rtc_info *info = dev_get_drvdata(dev);
50 	unsigned char value;
51 
52 	writeb(addr, info->index_reg);
53 	value = readb(info->data_reg);
54 
55 	return value;
56 }
57 
m48t86_writeb(struct device * dev,unsigned char value,unsigned long addr)58 static void m48t86_writeb(struct device *dev,
59 			  unsigned char value, unsigned long addr)
60 {
61 	struct m48t86_rtc_info *info = dev_get_drvdata(dev);
62 
63 	writeb(addr, info->index_reg);
64 	writeb(value, info->data_reg);
65 }
66 
m48t86_rtc_read_time(struct device * dev,struct rtc_time * tm)67 static int m48t86_rtc_read_time(struct device *dev, struct rtc_time *tm)
68 {
69 	unsigned char reg;
70 
71 	reg = m48t86_readb(dev, M48T86_B);
72 
73 	if (reg & M48T86_B_DM) {
74 		/* data (binary) mode */
75 		tm->tm_sec	= m48t86_readb(dev, M48T86_SEC);
76 		tm->tm_min	= m48t86_readb(dev, M48T86_MIN);
77 		tm->tm_hour	= m48t86_readb(dev, M48T86_HOUR) & 0x3f;
78 		tm->tm_mday	= m48t86_readb(dev, M48T86_DOM);
79 		/* tm_mon is 0-11 */
80 		tm->tm_mon	= m48t86_readb(dev, M48T86_MONTH) - 1;
81 		tm->tm_year	= m48t86_readb(dev, M48T86_YEAR) + 100;
82 		tm->tm_wday	= m48t86_readb(dev, M48T86_DOW);
83 	} else {
84 		/* bcd mode */
85 		tm->tm_sec	= bcd2bin(m48t86_readb(dev, M48T86_SEC));
86 		tm->tm_min	= bcd2bin(m48t86_readb(dev, M48T86_MIN));
87 		tm->tm_hour	= bcd2bin(m48t86_readb(dev, M48T86_HOUR) &
88 					  0x3f);
89 		tm->tm_mday	= bcd2bin(m48t86_readb(dev, M48T86_DOM));
90 		/* tm_mon is 0-11 */
91 		tm->tm_mon	= bcd2bin(m48t86_readb(dev, M48T86_MONTH)) - 1;
92 		tm->tm_year	= bcd2bin(m48t86_readb(dev, M48T86_YEAR)) + 100;
93 		tm->tm_wday	= bcd2bin(m48t86_readb(dev, M48T86_DOW));
94 	}
95 
96 	/* correct the hour if the clock is in 12h mode */
97 	if (!(reg & M48T86_B_H24))
98 		if (m48t86_readb(dev, M48T86_HOUR) & 0x80)
99 			tm->tm_hour += 12;
100 
101 	return 0;
102 }
103 
m48t86_rtc_set_time(struct device * dev,struct rtc_time * tm)104 static int m48t86_rtc_set_time(struct device *dev, struct rtc_time *tm)
105 {
106 	unsigned char reg;
107 
108 	reg = m48t86_readb(dev, M48T86_B);
109 
110 	/* update flag and 24h mode */
111 	reg |= M48T86_B_SET | M48T86_B_H24;
112 	m48t86_writeb(dev, reg, M48T86_B);
113 
114 	if (reg & M48T86_B_DM) {
115 		/* data (binary) mode */
116 		m48t86_writeb(dev, tm->tm_sec, M48T86_SEC);
117 		m48t86_writeb(dev, tm->tm_min, M48T86_MIN);
118 		m48t86_writeb(dev, tm->tm_hour, M48T86_HOUR);
119 		m48t86_writeb(dev, tm->tm_mday, M48T86_DOM);
120 		m48t86_writeb(dev, tm->tm_mon + 1, M48T86_MONTH);
121 		m48t86_writeb(dev, tm->tm_year % 100, M48T86_YEAR);
122 		m48t86_writeb(dev, tm->tm_wday, M48T86_DOW);
123 	} else {
124 		/* bcd mode */
125 		m48t86_writeb(dev, bin2bcd(tm->tm_sec), M48T86_SEC);
126 		m48t86_writeb(dev, bin2bcd(tm->tm_min), M48T86_MIN);
127 		m48t86_writeb(dev, bin2bcd(tm->tm_hour), M48T86_HOUR);
128 		m48t86_writeb(dev, bin2bcd(tm->tm_mday), M48T86_DOM);
129 		m48t86_writeb(dev, bin2bcd(tm->tm_mon + 1), M48T86_MONTH);
130 		m48t86_writeb(dev, bin2bcd(tm->tm_year % 100), M48T86_YEAR);
131 		m48t86_writeb(dev, bin2bcd(tm->tm_wday), M48T86_DOW);
132 	}
133 
134 	/* update ended */
135 	reg &= ~M48T86_B_SET;
136 	m48t86_writeb(dev, reg, M48T86_B);
137 
138 	return 0;
139 }
140 
m48t86_rtc_proc(struct device * dev,struct seq_file * seq)141 static int m48t86_rtc_proc(struct device *dev, struct seq_file *seq)
142 {
143 	unsigned char reg;
144 
145 	reg = m48t86_readb(dev, M48T86_B);
146 
147 	seq_printf(seq, "mode\t\t: %s\n",
148 		   (reg & M48T86_B_DM) ? "binary" : "bcd");
149 
150 	reg = m48t86_readb(dev, M48T86_D);
151 
152 	seq_printf(seq, "battery\t\t: %s\n",
153 		   (reg & M48T86_D_VRT) ? "ok" : "exhausted");
154 
155 	return 0;
156 }
157 
158 static const struct rtc_class_ops m48t86_rtc_ops = {
159 	.read_time	= m48t86_rtc_read_time,
160 	.set_time	= m48t86_rtc_set_time,
161 	.proc		= m48t86_rtc_proc,
162 };
163 
m48t86_nvram_read(void * priv,unsigned int off,void * buf,size_t count)164 static int m48t86_nvram_read(void *priv, unsigned int off, void *buf,
165 			     size_t count)
166 {
167 	struct device *dev = priv;
168 	unsigned int i;
169 
170 	for (i = 0; i < count; i++)
171 		((u8 *)buf)[i] = m48t86_readb(dev, M48T86_NVRAM(off + i));
172 
173 	return 0;
174 }
175 
m48t86_nvram_write(void * priv,unsigned int off,void * buf,size_t count)176 static int m48t86_nvram_write(void *priv, unsigned int off, void *buf,
177 			      size_t count)
178 {
179 	struct device *dev = priv;
180 	unsigned int i;
181 
182 	for (i = 0; i < count; i++)
183 		m48t86_writeb(dev, ((u8 *)buf)[i], M48T86_NVRAM(off + i));
184 
185 	return 0;
186 }
187 
188 /*
189  * The RTC is an optional feature at purchase time on some Technologic Systems
190  * boards. Verify that it actually exists by checking if the last two bytes
191  * of the NVRAM can be changed.
192  *
193  * This is based on the method used in their rtc7800.c example.
194  */
m48t86_verify_chip(struct platform_device * pdev)195 static bool m48t86_verify_chip(struct platform_device *pdev)
196 {
197 	unsigned int offset0 = M48T86_NVRAM(M48T86_NVRAM_LEN - 2);
198 	unsigned int offset1 = M48T86_NVRAM(M48T86_NVRAM_LEN - 1);
199 	unsigned char tmp0, tmp1;
200 
201 	tmp0 = m48t86_readb(&pdev->dev, offset0);
202 	tmp1 = m48t86_readb(&pdev->dev, offset1);
203 
204 	m48t86_writeb(&pdev->dev, 0x00, offset0);
205 	m48t86_writeb(&pdev->dev, 0x55, offset1);
206 	if (m48t86_readb(&pdev->dev, offset1) == 0x55) {
207 		m48t86_writeb(&pdev->dev, 0xaa, offset1);
208 		if (m48t86_readb(&pdev->dev, offset1) == 0xaa &&
209 		    m48t86_readb(&pdev->dev, offset0) == 0x00) {
210 			m48t86_writeb(&pdev->dev, tmp0, offset0);
211 			m48t86_writeb(&pdev->dev, tmp1, offset1);
212 
213 			return true;
214 		}
215 	}
216 	return false;
217 }
218 
m48t86_rtc_probe(struct platform_device * pdev)219 static int m48t86_rtc_probe(struct platform_device *pdev)
220 {
221 	struct m48t86_rtc_info *info;
222 	unsigned char reg;
223 	int err;
224 	struct nvmem_config m48t86_nvmem_cfg = {
225 		.name = "m48t86_nvram",
226 		.word_size = 1,
227 		.stride = 1,
228 		.size = M48T86_NVRAM_LEN,
229 		.reg_read = m48t86_nvram_read,
230 		.reg_write = m48t86_nvram_write,
231 		.priv = &pdev->dev,
232 	};
233 
234 	info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
235 	if (!info)
236 		return -ENOMEM;
237 
238 	info->index_reg = devm_platform_ioremap_resource(pdev, 0);
239 	if (IS_ERR(info->index_reg))
240 		return PTR_ERR(info->index_reg);
241 
242 	info->data_reg = devm_platform_ioremap_resource(pdev, 1);
243 	if (IS_ERR(info->data_reg))
244 		return PTR_ERR(info->data_reg);
245 
246 	dev_set_drvdata(&pdev->dev, info);
247 
248 	if (!m48t86_verify_chip(pdev)) {
249 		dev_info(&pdev->dev, "RTC not present\n");
250 		return -ENODEV;
251 	}
252 
253 	info->rtc = devm_rtc_allocate_device(&pdev->dev);
254 	if (IS_ERR(info->rtc))
255 		return PTR_ERR(info->rtc);
256 
257 	info->rtc->ops = &m48t86_rtc_ops;
258 
259 	err = devm_rtc_register_device(info->rtc);
260 	if (err)
261 		return err;
262 
263 	devm_rtc_nvmem_register(info->rtc, &m48t86_nvmem_cfg);
264 
265 	/* read battery status */
266 	reg = m48t86_readb(&pdev->dev, M48T86_D);
267 	dev_info(&pdev->dev, "battery %s\n",
268 		 (reg & M48T86_D_VRT) ? "ok" : "exhausted");
269 
270 	return 0;
271 }
272 
273 static const struct of_device_id m48t86_rtc_of_ids[] = {
274 	{ .compatible = "st,m48t86" },
275 	{ /* sentinel */ }
276 };
277 MODULE_DEVICE_TABLE(of, m48t86_rtc_of_ids);
278 
279 static struct platform_driver m48t86_rtc_platform_driver = {
280 	.driver		= {
281 		.name	= "rtc-m48t86",
282 		.of_match_table = m48t86_rtc_of_ids,
283 	},
284 	.probe		= m48t86_rtc_probe,
285 };
286 
287 module_platform_driver(m48t86_rtc_platform_driver);
288 
289 MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
290 MODULE_DESCRIPTION("M48T86 RTC driver");
291 MODULE_LICENSE("GPL");
292 MODULE_ALIAS("platform:rtc-m48t86");
293