1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *
4  * Driver for ST M41T93 SPI RTC
5  *
6  * (c) 2010 Nikolaus Voss, Weinmann Medical GmbH
7  */
8 
9 #include <linux/bcd.h>
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/platform_device.h>
13 #include <linux/rtc.h>
14 #include <linux/spi/spi.h>
15 
16 #define M41T93_REG_SSEC			0
17 #define M41T93_REG_ST_SEC		1
18 #define M41T93_REG_MIN			2
19 #define M41T93_REG_CENT_HOUR		3
20 #define M41T93_REG_WDAY			4
21 #define M41T93_REG_DAY			5
22 #define M41T93_REG_MON			6
23 #define M41T93_REG_YEAR			7
24 
25 
26 #define M41T93_REG_ALM_HOUR_HT		0xc
27 #define M41T93_REG_FLAGS		0xf
28 
29 #define M41T93_FLAG_ST			(1 << 7)
30 #define M41T93_FLAG_OF			(1 << 2)
31 #define M41T93_FLAG_BL			(1 << 4)
32 #define M41T93_FLAG_HT			(1 << 6)
33 
m41t93_set_reg(struct spi_device * spi,u8 addr,u8 data)34 static inline int m41t93_set_reg(struct spi_device *spi, u8 addr, u8 data)
35 {
36 	u8 buf[2];
37 
38 	/* MSB must be '1' to write */
39 	buf[0] = addr | 0x80;
40 	buf[1] = data;
41 
42 	return spi_write(spi, buf, sizeof(buf));
43 }
44 
m41t93_set_time(struct device * dev,struct rtc_time * tm)45 static int m41t93_set_time(struct device *dev, struct rtc_time *tm)
46 {
47 	struct spi_device *spi = to_spi_device(dev);
48 	int tmp;
49 	u8 buf[9] = {0x80};        /* write cmd + 8 data bytes */
50 	u8 * const data = &buf[1]; /* ptr to first data byte */
51 
52 	dev_dbg(dev, "%s secs=%d, mins=%d, "
53 		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
54 		"write", tm->tm_sec, tm->tm_min,
55 		tm->tm_hour, tm->tm_mday,
56 		tm->tm_mon, tm->tm_year, tm->tm_wday);
57 
58 	if (tm->tm_year < 100) {
59 		dev_warn(&spi->dev, "unsupported date (before 2000-01-01).\n");
60 		return -EINVAL;
61 	}
62 
63 	tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
64 	if (tmp < 0)
65 		return tmp;
66 
67 	if (tmp & M41T93_FLAG_OF) {
68 		dev_warn(&spi->dev, "OF bit is set, resetting.\n");
69 		m41t93_set_reg(spi, M41T93_REG_FLAGS, tmp & ~M41T93_FLAG_OF);
70 
71 		tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
72 		if (tmp < 0) {
73 			return tmp;
74 		} else if (tmp & M41T93_FLAG_OF) {
75 			/* OF cannot be immediately reset: oscillator has to be
76 			 * restarted. */
77 			u8 reset_osc = buf[M41T93_REG_ST_SEC] | M41T93_FLAG_ST;
78 
79 			dev_warn(&spi->dev,
80 				 "OF bit is still set, kickstarting clock.\n");
81 			m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);
82 			reset_osc &= ~M41T93_FLAG_ST;
83 			m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);
84 		}
85 	}
86 
87 	data[M41T93_REG_SSEC]		= 0;
88 	data[M41T93_REG_ST_SEC]		= bin2bcd(tm->tm_sec);
89 	data[M41T93_REG_MIN]		= bin2bcd(tm->tm_min);
90 	data[M41T93_REG_CENT_HOUR]	= bin2bcd(tm->tm_hour) |
91 						((tm->tm_year/100-1) << 6);
92 	data[M41T93_REG_DAY]		= bin2bcd(tm->tm_mday);
93 	data[M41T93_REG_WDAY]		= bin2bcd(tm->tm_wday + 1);
94 	data[M41T93_REG_MON]		= bin2bcd(tm->tm_mon + 1);
95 	data[M41T93_REG_YEAR]		= bin2bcd(tm->tm_year % 100);
96 
97 	return spi_write(spi, buf, sizeof(buf));
98 }
99 
100 
m41t93_get_time(struct device * dev,struct rtc_time * tm)101 static int m41t93_get_time(struct device *dev, struct rtc_time *tm)
102 {
103 	struct spi_device *spi = to_spi_device(dev);
104 	const u8 start_addr = 0;
105 	u8 buf[8];
106 	int century_after_1900;
107 	int tmp;
108 	int ret = 0;
109 
110 	/* Check status of clock. Two states must be considered:
111 	   1. halt bit (HT) is set: the clock is running but update of readout
112 	      registers has been disabled due to power failure. This is normal
113 	      case after poweron. Time is valid after resetting HT bit.
114 	   2. oscillator fail bit (OF) is set: time is invalid.
115 	*/
116 	tmp = spi_w8r8(spi, M41T93_REG_ALM_HOUR_HT);
117 	if (tmp < 0)
118 		return tmp;
119 
120 	if (tmp & M41T93_FLAG_HT) {
121 		dev_dbg(&spi->dev, "HT bit is set, reenable clock update.\n");
122 		m41t93_set_reg(spi, M41T93_REG_ALM_HOUR_HT,
123 			       tmp & ~M41T93_FLAG_HT);
124 	}
125 
126 	tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
127 	if (tmp < 0)
128 		return tmp;
129 
130 	if (tmp & M41T93_FLAG_OF) {
131 		ret = -EINVAL;
132 		dev_warn(&spi->dev, "OF bit is set, write time to restart.\n");
133 	}
134 
135 	if (tmp & M41T93_FLAG_BL)
136 		dev_warn(&spi->dev, "BL bit is set, replace battery.\n");
137 
138 	/* read actual time/date */
139 	tmp = spi_write_then_read(spi, &start_addr, 1, buf, sizeof(buf));
140 	if (tmp < 0)
141 		return tmp;
142 
143 	tm->tm_sec	= bcd2bin(buf[M41T93_REG_ST_SEC]);
144 	tm->tm_min	= bcd2bin(buf[M41T93_REG_MIN]);
145 	tm->tm_hour	= bcd2bin(buf[M41T93_REG_CENT_HOUR] & 0x3f);
146 	tm->tm_mday	= bcd2bin(buf[M41T93_REG_DAY]);
147 	tm->tm_mon	= bcd2bin(buf[M41T93_REG_MON]) - 1;
148 	tm->tm_wday	= bcd2bin(buf[M41T93_REG_WDAY] & 0x0f) - 1;
149 
150 	century_after_1900 = (buf[M41T93_REG_CENT_HOUR] >> 6) + 1;
151 	tm->tm_year = bcd2bin(buf[M41T93_REG_YEAR]) + century_after_1900 * 100;
152 
153 	dev_dbg(dev, "%s secs=%d, mins=%d, "
154 		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
155 		"read", tm->tm_sec, tm->tm_min,
156 		tm->tm_hour, tm->tm_mday,
157 		tm->tm_mon, tm->tm_year, tm->tm_wday);
158 
159 	return ret;
160 }
161 
162 
163 static const struct rtc_class_ops m41t93_rtc_ops = {
164 	.read_time	= m41t93_get_time,
165 	.set_time	= m41t93_set_time,
166 };
167 
168 static struct spi_driver m41t93_driver;
169 
m41t93_probe(struct spi_device * spi)170 static int m41t93_probe(struct spi_device *spi)
171 {
172 	struct rtc_device *rtc;
173 	int res;
174 
175 	spi->bits_per_word = 8;
176 	spi_setup(spi);
177 
178 	res = spi_w8r8(spi, M41T93_REG_WDAY);
179 	if (res < 0 || (res & 0xf8) != 0) {
180 		dev_err(&spi->dev, "not found 0x%x.\n", res);
181 		return -ENODEV;
182 	}
183 
184 	rtc = devm_rtc_device_register(&spi->dev, m41t93_driver.driver.name,
185 					&m41t93_rtc_ops, THIS_MODULE);
186 	if (IS_ERR(rtc))
187 		return PTR_ERR(rtc);
188 
189 	spi_set_drvdata(spi, rtc);
190 
191 	return 0;
192 }
193 
194 static struct spi_driver m41t93_driver = {
195 	.driver = {
196 		.name	= "rtc-m41t93",
197 	},
198 	.probe	= m41t93_probe,
199 };
200 
201 module_spi_driver(m41t93_driver);
202 
203 MODULE_AUTHOR("Nikolaus Voss <n.voss@weinmann.de>");
204 MODULE_DESCRIPTION("Driver for ST M41T93 SPI RTC");
205 MODULE_LICENSE("GPL");
206 MODULE_ALIAS("spi:rtc-m41t93");
207