rtc-m48t86.c

  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};
 45
 46static unsigned char m48t86_readb(struct device *dev, unsigned long addr)
 47{
 48	struct m48t86_rtc_info *info = dev_get_drvdata(dev);
 49	unsigned char value;
 50
 51	writeb(addr, info->index_reg);
 52	value = readb(info->data_reg);
 53
 54	return value;
 55}
 56
 57static void m48t86_writeb(struct device *dev,
 58			  unsigned char value, unsigned long addr)
 59{
 60	struct m48t86_rtc_info *info = dev_get_drvdata(dev);
 61
 62	writeb(addr, info->index_reg);
 63	writeb(value, info->data_reg);
 64}
 65
 66static int m48t86_rtc_read_time(struct device *dev, struct rtc_time *tm)
 67{
 68	unsigned char reg;
 69
 70	reg = m48t86_readb(dev, M48T86_B);
 71
 72	if (reg & M48T86_B_DM) {
 73		/* data (binary) mode */
 74		tm->tm_sec	= m48t86_readb(dev, M48T86_SEC);
 75		tm->tm_min	= m48t86_readb(dev, M48T86_MIN);
 76		tm->tm_hour	= m48t86_readb(dev, M48T86_HOUR) & 0x3f;
 77		tm->tm_mday	= m48t86_readb(dev, M48T86_DOM);
 78		/* tm_mon is 0-11 */
 79		tm->tm_mon	= m48t86_readb(dev, M48T86_MONTH) - 1;
 80		tm->tm_year	= m48t86_readb(dev, M48T86_YEAR) + 100;
 81		tm->tm_wday	= m48t86_readb(dev, M48T86_DOW);
 82	} else {
 83		/* bcd mode */
 84		tm->tm_sec	= bcd2bin(m48t86_readb(dev, M48T86_SEC));
 85		tm->tm_min	= bcd2bin(m48t86_readb(dev, M48T86_MIN));
 86		tm->tm_hour	= bcd2bin(m48t86_readb(dev, M48T86_HOUR) &
 87					  0x3f);
 88		tm->tm_mday	= bcd2bin(m48t86_readb(dev, M48T86_DOM));
 89		/* tm_mon is 0-11 */
 90		tm->tm_mon	= bcd2bin(m48t86_readb(dev, M48T86_MONTH)) - 1;
 91		tm->tm_year	= bcd2bin(m48t86_readb(dev, M48T86_YEAR)) + 100;
 92		tm->tm_wday	= bcd2bin(m48t86_readb(dev, M48T86_DOW));
 93	}
 94
 95	/* correct the hour if the clock is in 12h mode */
 96	if (!(reg & M48T86_B_H24))
 97		if (m48t86_readb(dev, M48T86_HOUR) & 0x80)
 98			tm->tm_hour += 12;
 99
100	return 0;
101}
102
103static int m48t86_rtc_set_time(struct device *dev, struct rtc_time *tm)
104{
105	unsigned char reg;
106
107	reg = m48t86_readb(dev, M48T86_B);
108
109	/* update flag and 24h mode */
110	reg |= M48T86_B_SET | M48T86_B_H24;
111	m48t86_writeb(dev, reg, M48T86_B);
112
113	if (reg & M48T86_B_DM) {
114		/* data (binary) mode */
115		m48t86_writeb(dev, tm->tm_sec, M48T86_SEC);
116		m48t86_writeb(dev, tm->tm_min, M48T86_MIN);
117		m48t86_writeb(dev, tm->tm_hour, M48T86_HOUR);
118		m48t86_writeb(dev, tm->tm_mday, M48T86_DOM);
119		m48t86_writeb(dev, tm->tm_mon + 1, M48T86_MONTH);
120		m48t86_writeb(dev, tm->tm_year % 100, M48T86_YEAR);
121		m48t86_writeb(dev, tm->tm_wday, M48T86_DOW);
122	} else {
123		/* bcd mode */
124		m48t86_writeb(dev, bin2bcd(tm->tm_sec), M48T86_SEC);
125		m48t86_writeb(dev, bin2bcd(tm->tm_min), M48T86_MIN);
126		m48t86_writeb(dev, bin2bcd(tm->tm_hour), M48T86_HOUR);
127		m48t86_writeb(dev, bin2bcd(tm->tm_mday), M48T86_DOM);
128		m48t86_writeb(dev, bin2bcd(tm->tm_mon + 1), M48T86_MONTH);
129		m48t86_writeb(dev, bin2bcd(tm->tm_year % 100), M48T86_YEAR);
130		m48t86_writeb(dev, bin2bcd(tm->tm_wday), M48T86_DOW);
131	}
132
133	/* update ended */
134	reg &= ~M48T86_B_SET;
135	m48t86_writeb(dev, reg, M48T86_B);
136
137	return 0;
138}
139
140static int m48t86_rtc_proc(struct device *dev, struct seq_file *seq)
141{
142	unsigned char reg;
143
144	reg = m48t86_readb(dev, M48T86_B);
145
146	seq_printf(seq, "mode\t\t: %s\n",
147		   (reg & M48T86_B_DM) ? "binary" : "bcd");
148
149	reg = m48t86_readb(dev, M48T86_D);
150
151	seq_printf(seq, "battery\t\t: %s\n",
152		   (reg & M48T86_D_VRT) ? "ok" : "exhausted");
153
154	return 0;
155}
156
157static const struct rtc_class_ops m48t86_rtc_ops = {
158	.read_time	= m48t86_rtc_read_time,
159	.set_time	= m48t86_rtc_set_time,
160	.proc		= m48t86_rtc_proc,
161};
162
163static int m48t86_nvram_read(void *priv, unsigned int off, void *buf,
164			     size_t count)
165{
166	struct device *dev = priv;
167	unsigned int i;
168
169	for (i = 0; i < count; i++)
170		((u8 *)buf)[i] = m48t86_readb(dev, M48T86_NVRAM(off + i));
171
172	return 0;
173}
174
175static int m48t86_nvram_write(void *priv, unsigned int off, void *buf,
176			      size_t count)
177{
178	struct device *dev = priv;
179	unsigned int i;
180
181	for (i = 0; i < count; i++)
182		m48t86_writeb(dev, ((u8 *)buf)[i], M48T86_NVRAM(off + i));
183
184	return 0;
185}
186
187/*
188 * The RTC is an optional feature at purchase time on some Technologic Systems
189 * boards. Verify that it actually exists by checking if the last two bytes
190 * of the NVRAM can be changed.
191 *
192 * This is based on the method used in their rtc7800.c example.
193 */
194static bool m48t86_verify_chip(struct platform_device *pdev)
195{
196	unsigned int offset0 = M48T86_NVRAM(M48T86_NVRAM_LEN - 2);
197	unsigned int offset1 = M48T86_NVRAM(M48T86_NVRAM_LEN - 1);
198	unsigned char tmp0, tmp1;
199
200	tmp0 = m48t86_readb(&pdev->dev, offset0);
201	tmp1 = m48t86_readb(&pdev->dev, offset1);
202
203	m48t86_writeb(&pdev->dev, 0x00, offset0);
204	m48t86_writeb(&pdev->dev, 0x55, offset1);
205	if (m48t86_readb(&pdev->dev, offset1) == 0x55) {
206		m48t86_writeb(&pdev->dev, 0xaa, offset1);
207		if (m48t86_readb(&pdev->dev, offset1) == 0xaa &&
208		    m48t86_readb(&pdev->dev, offset0) == 0x00) {
209			m48t86_writeb(&pdev->dev, tmp0, offset0);
210			m48t86_writeb(&pdev->dev, tmp1, offset1);
211
212			return true;
213		}
214	}
215	return false;
216}
217
218static int m48t86_rtc_probe(struct platform_device *pdev)
219{
220	struct m48t86_rtc_info *info;
221	struct rtc_device *rtc;
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	rtc = devm_rtc_allocate_device(&pdev->dev);
254	if (IS_ERR(rtc))
255		return PTR_ERR(rtc);
256
257	rtc->ops = &m48t86_rtc_ops;
258
259	err = devm_rtc_register_device(rtc);
260	if (err)
261		return err;
262
263	devm_rtc_nvmem_register(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");