Root/drivers/rtc/rtc-m41t93.c

1/*
2 *
3 * Driver for ST M41T93 SPI RTC
4 *
5 * (c) 2010 Nikolaus Voss, Weinmann Medical GmbH
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
12#include <linux/bcd.h>
13#include <linux/kernel.h>
14#include <linux/module.h>
15#include <linux/platform_device.h>
16#include <linux/rtc.h>
17#include <linux/spi/spi.h>
18
19#define M41T93_REG_SSEC 0
20#define M41T93_REG_ST_SEC 1
21#define M41T93_REG_MIN 2
22#define M41T93_REG_CENT_HOUR 3
23#define M41T93_REG_WDAY 4
24#define M41T93_REG_DAY 5
25#define M41T93_REG_MON 6
26#define M41T93_REG_YEAR 7
27
28
29#define M41T93_REG_ALM_HOUR_HT 0xc
30#define M41T93_REG_FLAGS 0xf
31
32#define M41T93_FLAG_ST (1 << 7)
33#define M41T93_FLAG_OF (1 << 2)
34#define M41T93_FLAG_BL (1 << 4)
35#define M41T93_FLAG_HT (1 << 6)
36
37static inline int m41t93_set_reg(struct spi_device *spi, u8 addr, u8 data)
38{
39    u8 buf[2];
40
41    /* MSB must be '1' to write */
42    buf[0] = addr | 0x80;
43    buf[1] = data;
44
45    return spi_write(spi, buf, sizeof(buf));
46}
47
48static int m41t93_set_time(struct device *dev, struct rtc_time *tm)
49{
50    struct spi_device *spi = to_spi_device(dev);
51    int tmp;
52    u8 buf[9] = {0x80}; /* write cmd + 8 data bytes */
53    u8 * const data = &buf[1]; /* ptr to first data byte */
54
55    dev_dbg(dev, "%s secs=%d, mins=%d, "
56        "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
57        "write", tm->tm_sec, tm->tm_min,
58        tm->tm_hour, tm->tm_mday,
59        tm->tm_mon, tm->tm_year, tm->tm_wday);
60
61    if (tm->tm_year < 100) {
62        dev_warn(&spi->dev, "unsupported date (before 2000-01-01).\n");
63        return -EINVAL;
64    }
65
66    tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
67    if (tmp < 0)
68        return tmp;
69
70    if (tmp & M41T93_FLAG_OF) {
71        dev_warn(&spi->dev, "OF bit is set, resetting.\n");
72        m41t93_set_reg(spi, M41T93_REG_FLAGS, tmp & ~M41T93_FLAG_OF);
73
74        tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
75        if (tmp < 0) {
76            return tmp;
77        } else if (tmp & M41T93_FLAG_OF) {
78            /* OF cannot be immediately reset: oscillator has to be
79             * restarted. */
80            u8 reset_osc = buf[M41T93_REG_ST_SEC] | M41T93_FLAG_ST;
81
82            dev_warn(&spi->dev,
83                 "OF bit is still set, kickstarting clock.\n");
84            m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);
85            reset_osc &= ~M41T93_FLAG_ST;
86            m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);
87        }
88    }
89
90    data[M41T93_REG_SSEC] = 0;
91    data[M41T93_REG_ST_SEC] = bin2bcd(tm->tm_sec);
92    data[M41T93_REG_MIN] = bin2bcd(tm->tm_min);
93    data[M41T93_REG_CENT_HOUR] = bin2bcd(tm->tm_hour) |
94                        ((tm->tm_year/100-1) << 6);
95    data[M41T93_REG_DAY] = bin2bcd(tm->tm_mday);
96    data[M41T93_REG_WDAY] = bin2bcd(tm->tm_wday + 1);
97    data[M41T93_REG_MON] = bin2bcd(tm->tm_mon + 1);
98    data[M41T93_REG_YEAR] = bin2bcd(tm->tm_year % 100);
99
100    return spi_write(spi, buf, sizeof(buf));
101}
102
103
104static int m41t93_get_time(struct device *dev, struct rtc_time *tm)
105{
106    struct spi_device *spi = to_spi_device(dev);
107    const u8 start_addr = 0;
108    u8 buf[8];
109    int century_after_1900;
110    int tmp;
111    int ret = 0;
112
113    /* Check status of clock. Two states must be considered:
114       1. halt bit (HT) is set: the clock is running but update of readout
115          registers has been disabled due to power failure. This is normal
116          case after poweron. Time is valid after resetting HT bit.
117       2. oscillator fail bit (OF) is set: time is invalid.
118    */
119    tmp = spi_w8r8(spi, M41T93_REG_ALM_HOUR_HT);
120    if (tmp < 0)
121        return tmp;
122
123    if (tmp & M41T93_FLAG_HT) {
124        dev_dbg(&spi->dev, "HT bit is set, reenable clock update.\n");
125        m41t93_set_reg(spi, M41T93_REG_ALM_HOUR_HT,
126                   tmp & ~M41T93_FLAG_HT);
127    }
128
129    tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
130    if (tmp < 0)
131        return tmp;
132
133    if (tmp & M41T93_FLAG_OF) {
134        ret = -EINVAL;
135        dev_warn(&spi->dev, "OF bit is set, write time to restart.\n");
136    }
137
138    if (tmp & M41T93_FLAG_BL)
139        dev_warn(&spi->dev, "BL bit is set, replace battery.\n");
140
141    /* read actual time/date */
142    tmp = spi_write_then_read(spi, &start_addr, 1, buf, sizeof(buf));
143    if (tmp < 0)
144        return tmp;
145
146    tm->tm_sec = bcd2bin(buf[M41T93_REG_ST_SEC]);
147    tm->tm_min = bcd2bin(buf[M41T93_REG_MIN]);
148    tm->tm_hour = bcd2bin(buf[M41T93_REG_CENT_HOUR] & 0x3f);
149    tm->tm_mday = bcd2bin(buf[M41T93_REG_DAY]);
150    tm->tm_mon = bcd2bin(buf[M41T93_REG_MON]) - 1;
151    tm->tm_wday = bcd2bin(buf[M41T93_REG_WDAY] & 0x0f) - 1;
152
153    century_after_1900 = (buf[M41T93_REG_CENT_HOUR] >> 6) + 1;
154    tm->tm_year = bcd2bin(buf[M41T93_REG_YEAR]) + century_after_1900 * 100;
155
156    dev_dbg(dev, "%s secs=%d, mins=%d, "
157        "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
158        "read", tm->tm_sec, tm->tm_min,
159        tm->tm_hour, tm->tm_mday,
160        tm->tm_mon, tm->tm_year, tm->tm_wday);
161
162    return ret < 0 ? ret : rtc_valid_tm(tm);
163}
164
165
166static const struct rtc_class_ops m41t93_rtc_ops = {
167    .read_time = m41t93_get_time,
168    .set_time = m41t93_set_time,
169};
170
171static struct spi_driver m41t93_driver;
172
173static int __devinit m41t93_probe(struct spi_device *spi)
174{
175    struct rtc_device *rtc;
176    int res;
177
178    spi->bits_per_word = 8;
179    spi_setup(spi);
180
181    res = spi_w8r8(spi, M41T93_REG_WDAY);
182    if (res < 0 || (res & 0xf8) != 0) {
183        dev_err(&spi->dev, "not found 0x%x.\n", res);
184        return -ENODEV;
185    }
186
187    rtc = rtc_device_register(m41t93_driver.driver.name,
188        &spi->dev, &m41t93_rtc_ops, THIS_MODULE);
189    if (IS_ERR(rtc))
190        return PTR_ERR(rtc);
191
192    dev_set_drvdata(&spi->dev, rtc);
193
194    return 0;
195}
196
197
198static int __devexit m41t93_remove(struct spi_device *spi)
199{
200    struct rtc_device *rtc = spi_get_drvdata(spi);
201
202    if (rtc)
203        rtc_device_unregister(rtc);
204
205    return 0;
206}
207
208static struct spi_driver m41t93_driver = {
209    .driver = {
210        .name = "rtc-m41t93",
211        .owner = THIS_MODULE,
212    },
213    .probe = m41t93_probe,
214    .remove = __devexit_p(m41t93_remove),
215};
216
217module_spi_driver(m41t93_driver);
218
219MODULE_AUTHOR("Nikolaus Voss <n.voss@weinmann.de>");
220MODULE_DESCRIPTION("Driver for ST M41T93 SPI RTC");
221MODULE_LICENSE("GPL");
222MODULE_ALIAS("spi:rtc-m41t93");
223

Archive Download this file



interactive