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