1 /*
2 * ST M48T86 / Dallas DS12887 RTC driver
3 * Copyright (c) 2006 Tower Technologies
4 *
5 * Author: Alessandro Zummo <a.zummo@towertech.it>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * This drivers only supports the clock running in BCD and 24H mode.
12 * If it will be ever adapted to binary and 12H mode, care must be taken
13 * to not introduce bugs.
14 */
15
16 #include <linux/module.h>
17 #include <linux/rtc.h>
18 #include <linux/platform_device.h>
19 #include <linux/bcd.h>
20 #include <linux/io.h>
21
22 #define M48T86_SEC 0x00
23 #define M48T86_SECALRM 0x01
24 #define M48T86_MIN 0x02
25 #define M48T86_MINALRM 0x03
26 #define M48T86_HOUR 0x04
27 #define M48T86_HOURALRM 0x05
28 #define M48T86_DOW 0x06 /* 1 = sunday */
29 #define M48T86_DOM 0x07
30 #define M48T86_MONTH 0x08 /* 1 - 12 */
31 #define M48T86_YEAR 0x09 /* 0 - 99 */
32 #define M48T86_A 0x0a
33 #define M48T86_B 0x0b
34 #define M48T86_B_SET BIT(7)
35 #define M48T86_B_DM BIT(2)
36 #define M48T86_B_H24 BIT(1)
37 #define M48T86_C 0x0c
38 #define M48T86_D 0x0d
39 #define M48T86_D_VRT BIT(7)
40 #define M48T86_NVRAM(x) (0x0e + (x))
41 #define M48T86_NVRAM_LEN 114
42
43 struct m48t86_rtc_info {
44 void __iomem *index_reg;
45 void __iomem *data_reg;
46 struct rtc_device *rtc;
47 };
48
m48t86_readb(struct device * dev,unsigned long addr)49 static unsigned char m48t86_readb(struct device *dev, unsigned long addr)
50 {
51 struct m48t86_rtc_info *info = dev_get_drvdata(dev);
52 unsigned char value;
53
54 writeb(addr, info->index_reg);
55 value = readb(info->data_reg);
56
57 return value;
58 }
59
m48t86_writeb(struct device * dev,unsigned char value,unsigned long addr)60 static void m48t86_writeb(struct device *dev,
61 unsigned char value, unsigned long addr)
62 {
63 struct m48t86_rtc_info *info = dev_get_drvdata(dev);
64
65 writeb(addr, info->index_reg);
66 writeb(value, info->data_reg);
67 }
68
m48t86_rtc_read_time(struct device * dev,struct rtc_time * tm)69 static int m48t86_rtc_read_time(struct device *dev, struct rtc_time *tm)
70 {
71 unsigned char reg;
72
73 reg = m48t86_readb(dev, M48T86_B);
74
75 if (reg & M48T86_B_DM) {
76 /* data (binary) mode */
77 tm->tm_sec = m48t86_readb(dev, M48T86_SEC);
78 tm->tm_min = m48t86_readb(dev, M48T86_MIN);
79 tm->tm_hour = m48t86_readb(dev, M48T86_HOUR) & 0x3f;
80 tm->tm_mday = m48t86_readb(dev, M48T86_DOM);
81 /* tm_mon is 0-11 */
82 tm->tm_mon = m48t86_readb(dev, M48T86_MONTH) - 1;
83 tm->tm_year = m48t86_readb(dev, M48T86_YEAR) + 100;
84 tm->tm_wday = m48t86_readb(dev, M48T86_DOW);
85 } else {
86 /* bcd mode */
87 tm->tm_sec = bcd2bin(m48t86_readb(dev, M48T86_SEC));
88 tm->tm_min = bcd2bin(m48t86_readb(dev, M48T86_MIN));
89 tm->tm_hour = bcd2bin(m48t86_readb(dev, M48T86_HOUR) &
90 0x3f);
91 tm->tm_mday = bcd2bin(m48t86_readb(dev, M48T86_DOM));
92 /* tm_mon is 0-11 */
93 tm->tm_mon = bcd2bin(m48t86_readb(dev, M48T86_MONTH)) - 1;
94 tm->tm_year = bcd2bin(m48t86_readb(dev, M48T86_YEAR)) + 100;
95 tm->tm_wday = bcd2bin(m48t86_readb(dev, M48T86_DOW));
96 }
97
98 /* correct the hour if the clock is in 12h mode */
99 if (!(reg & M48T86_B_H24))
100 if (m48t86_readb(dev, M48T86_HOUR) & 0x80)
101 tm->tm_hour += 12;
102
103 return 0;
104 }
105
m48t86_rtc_set_time(struct device * dev,struct rtc_time * tm)106 static int m48t86_rtc_set_time(struct device *dev, struct rtc_time *tm)
107 {
108 unsigned char reg;
109
110 reg = m48t86_readb(dev, M48T86_B);
111
112 /* update flag and 24h mode */
113 reg |= M48T86_B_SET | M48T86_B_H24;
114 m48t86_writeb(dev, reg, M48T86_B);
115
116 if (reg & M48T86_B_DM) {
117 /* data (binary) mode */
118 m48t86_writeb(dev, tm->tm_sec, M48T86_SEC);
119 m48t86_writeb(dev, tm->tm_min, M48T86_MIN);
120 m48t86_writeb(dev, tm->tm_hour, M48T86_HOUR);
121 m48t86_writeb(dev, tm->tm_mday, M48T86_DOM);
122 m48t86_writeb(dev, tm->tm_mon + 1, M48T86_MONTH);
123 m48t86_writeb(dev, tm->tm_year % 100, M48T86_YEAR);
124 m48t86_writeb(dev, tm->tm_wday, M48T86_DOW);
125 } else {
126 /* bcd mode */
127 m48t86_writeb(dev, bin2bcd(tm->tm_sec), M48T86_SEC);
128 m48t86_writeb(dev, bin2bcd(tm->tm_min), M48T86_MIN);
129 m48t86_writeb(dev, bin2bcd(tm->tm_hour), M48T86_HOUR);
130 m48t86_writeb(dev, bin2bcd(tm->tm_mday), M48T86_DOM);
131 m48t86_writeb(dev, bin2bcd(tm->tm_mon + 1), M48T86_MONTH);
132 m48t86_writeb(dev, bin2bcd(tm->tm_year % 100), M48T86_YEAR);
133 m48t86_writeb(dev, bin2bcd(tm->tm_wday), M48T86_DOW);
134 }
135
136 /* update ended */
137 reg &= ~M48T86_B_SET;
138 m48t86_writeb(dev, reg, M48T86_B);
139
140 return 0;
141 }
142
m48t86_rtc_proc(struct device * dev,struct seq_file * seq)143 static int m48t86_rtc_proc(struct device *dev, struct seq_file *seq)
144 {
145 unsigned char reg;
146
147 reg = m48t86_readb(dev, M48T86_B);
148
149 seq_printf(seq, "mode\t\t: %s\n",
150 (reg & M48T86_B_DM) ? "binary" : "bcd");
151
152 reg = m48t86_readb(dev, M48T86_D);
153
154 seq_printf(seq, "battery\t\t: %s\n",
155 (reg & M48T86_D_VRT) ? "ok" : "exhausted");
156
157 return 0;
158 }
159
160 static const struct rtc_class_ops m48t86_rtc_ops = {
161 .read_time = m48t86_rtc_read_time,
162 .set_time = m48t86_rtc_set_time,
163 .proc = m48t86_rtc_proc,
164 };
165
m48t86_nvram_read(void * priv,unsigned int off,void * buf,size_t count)166 static int m48t86_nvram_read(void *priv, unsigned int off, void *buf,
167 size_t count)
168 {
169 struct device *dev = priv;
170 unsigned int i;
171
172 for (i = 0; i < count; i++)
173 ((u8 *)buf)[i] = m48t86_readb(dev, M48T86_NVRAM(off + i));
174
175 return 0;
176 }
177
m48t86_nvram_write(void * priv,unsigned int off,void * buf,size_t count)178 static int m48t86_nvram_write(void *priv, unsigned int off, void *buf,
179 size_t count)
180 {
181 struct device *dev = priv;
182 unsigned int i;
183
184 for (i = 0; i < count; i++)
185 m48t86_writeb(dev, ((u8 *)buf)[i], M48T86_NVRAM(off + i));
186
187 return 0;
188 }
189
190 /*
191 * The RTC is an optional feature at purchase time on some Technologic Systems
192 * boards. Verify that it actually exists by checking if the last two bytes
193 * of the NVRAM can be changed.
194 *
195 * This is based on the method used in their rtc7800.c example.
196 */
m48t86_verify_chip(struct platform_device * pdev)197 static bool m48t86_verify_chip(struct platform_device *pdev)
198 {
199 unsigned int offset0 = M48T86_NVRAM(M48T86_NVRAM_LEN - 2);
200 unsigned int offset1 = M48T86_NVRAM(M48T86_NVRAM_LEN - 1);
201 unsigned char tmp0, tmp1;
202
203 tmp0 = m48t86_readb(&pdev->dev, offset0);
204 tmp1 = m48t86_readb(&pdev->dev, offset1);
205
206 m48t86_writeb(&pdev->dev, 0x00, offset0);
207 m48t86_writeb(&pdev->dev, 0x55, offset1);
208 if (m48t86_readb(&pdev->dev, offset1) == 0x55) {
209 m48t86_writeb(&pdev->dev, 0xaa, offset1);
210 if (m48t86_readb(&pdev->dev, offset1) == 0xaa &&
211 m48t86_readb(&pdev->dev, offset0) == 0x00) {
212 m48t86_writeb(&pdev->dev, tmp0, offset0);
213 m48t86_writeb(&pdev->dev, tmp1, offset1);
214
215 return true;
216 }
217 }
218 return false;
219 }
220
m48t86_rtc_probe(struct platform_device * pdev)221 static int m48t86_rtc_probe(struct platform_device *pdev)
222 {
223 struct m48t86_rtc_info *info;
224 struct resource *res;
225 unsigned char reg;
226 int err;
227 struct nvmem_config m48t86_nvmem_cfg = {
228 .name = "m48t86_nvram",
229 .word_size = 1,
230 .stride = 1,
231 .size = M48T86_NVRAM_LEN,
232 .reg_read = m48t86_nvram_read,
233 .reg_write = m48t86_nvram_write,
234 .priv = &pdev->dev,
235 };
236
237 info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
238 if (!info)
239 return -ENOMEM;
240
241 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
242 if (!res)
243 return -ENODEV;
244 info->index_reg = devm_ioremap_resource(&pdev->dev, res);
245 if (IS_ERR(info->index_reg))
246 return PTR_ERR(info->index_reg);
247
248 res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
249 if (!res)
250 return -ENODEV;
251 info->data_reg = devm_ioremap_resource(&pdev->dev, res);
252 if (IS_ERR(info->data_reg))
253 return PTR_ERR(info->data_reg);
254
255 dev_set_drvdata(&pdev->dev, info);
256
257 if (!m48t86_verify_chip(pdev)) {
258 dev_info(&pdev->dev, "RTC not present\n");
259 return -ENODEV;
260 }
261
262 info->rtc = devm_rtc_allocate_device(&pdev->dev);
263 if (IS_ERR(info->rtc))
264 return PTR_ERR(info->rtc);
265
266 info->rtc->ops = &m48t86_rtc_ops;
267 info->rtc->nvram_old_abi = true;
268
269 err = rtc_register_device(info->rtc);
270 if (err)
271 return err;
272
273 rtc_nvmem_register(info->rtc, &m48t86_nvmem_cfg);
274
275 /* read battery status */
276 reg = m48t86_readb(&pdev->dev, M48T86_D);
277 dev_info(&pdev->dev, "battery %s\n",
278 (reg & M48T86_D_VRT) ? "ok" : "exhausted");
279
280 return 0;
281 }
282
283 static struct platform_driver m48t86_rtc_platform_driver = {
284 .driver = {
285 .name = "rtc-m48t86",
286 },
287 .probe = m48t86_rtc_probe,
288 };
289
290 module_platform_driver(m48t86_rtc_platform_driver);
291
292 MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
293 MODULE_DESCRIPTION("M48T86 RTC driver");
294 MODULE_LICENSE("GPL");
295 MODULE_ALIAS("platform:rtc-m48t86");
296