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
41struct m48t86_rtc_info {
42	void __iomem *index_reg;
43	void __iomem *data_reg;
44	struct rtc_device *rtc;
45};
46
47static 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
58static 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
67static 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
104static 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
141static 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
158static 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
164static 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
176static 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 */
195static 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
219static 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
273static const struct of_device_id m48t86_rtc_of_ids[] = {
274	{ .compatible = "st,m48t86" },
275	{ /* sentinel */ }
276};
277MODULE_DEVICE_TABLE(of, m48t86_rtc_of_ids);
278
279static 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
287module_platform_driver(m48t86_rtc_platform_driver);
288
289MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
290MODULE_DESCRIPTION("M48T86 RTC driver");
291MODULE_LICENSE("GPL");
292MODULE_ALIAS("platform:rtc-m48t86");
293