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Linux/drivers/rtc/rtc-ds1302.c

  1 /*
  2  * Dallas DS1302 RTC Support
  3  *
  4  *  Copyright (C) 2002 David McCullough
  5  *  Copyright (C) 2003 - 2007 Paul Mundt
  6  *
  7  * This file is subject to the terms and conditions of the GNU General Public
  8  * License version 2. See the file "COPYING" in the main directory of
  9  * this archive for more details.
 10  */
 11 
 12 #include <linux/bcd.h>
 13 #include <linux/init.h>
 14 #include <linux/io.h>
 15 #include <linux/kernel.h>
 16 #include <linux/module.h>
 17 #include <linux/of.h>
 18 #include <linux/rtc.h>
 19 #include <linux/spi/spi.h>
 20 
 21 #define DRV_NAME        "rtc-ds1302"
 22 
 23 #define RTC_CMD_READ    0x81            /* Read command */
 24 #define RTC_CMD_WRITE   0x80            /* Write command */
 25 
 26 #define RTC_CMD_WRITE_ENABLE    0x00            /* Write enable */
 27 #define RTC_CMD_WRITE_DISABLE   0x80            /* Write disable */
 28 
 29 #define RTC_ADDR_RAM0   0x20            /* Address of RAM0 */
 30 #define RTC_ADDR_TCR    0x08            /* Address of trickle charge register */
 31 #define RTC_CLCK_BURST  0x1F            /* Address of clock burst */
 32 #define RTC_CLCK_LEN    0x08            /* Size of clock burst */
 33 #define RTC_ADDR_CTRL   0x07            /* Address of control register */
 34 #define RTC_ADDR_YEAR   0x06            /* Address of year register */
 35 #define RTC_ADDR_DAY    0x05            /* Address of day of week register */
 36 #define RTC_ADDR_MON    0x04            /* Address of month register */
 37 #define RTC_ADDR_DATE   0x03            /* Address of day of month register */
 38 #define RTC_ADDR_HOUR   0x02            /* Address of hour register */
 39 #define RTC_ADDR_MIN    0x01            /* Address of minute register */
 40 #define RTC_ADDR_SEC    0x00            /* Address of second register */
 41 
 42 static int ds1302_rtc_set_time(struct device *dev, struct rtc_time *time)
 43 {
 44         struct spi_device       *spi = dev_get_drvdata(dev);
 45         u8              buf[1 + RTC_CLCK_LEN];
 46         u8              *bp = buf;
 47         int             status;
 48 
 49         /* Enable writing */
 50         bp = buf;
 51         *bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
 52         *bp++ = RTC_CMD_WRITE_ENABLE;
 53 
 54         status = spi_write_then_read(spi, buf, 2,
 55                         NULL, 0);
 56         if (status)
 57                 return status;
 58 
 59         /* Write registers starting at the first time/date address. */
 60         bp = buf;
 61         *bp++ = RTC_CLCK_BURST << 1 | RTC_CMD_WRITE;
 62 
 63         *bp++ = bin2bcd(time->tm_sec);
 64         *bp++ = bin2bcd(time->tm_min);
 65         *bp++ = bin2bcd(time->tm_hour);
 66         *bp++ = bin2bcd(time->tm_mday);
 67         *bp++ = bin2bcd(time->tm_mon + 1);
 68         *bp++ = time->tm_wday + 1;
 69         *bp++ = bin2bcd(time->tm_year % 100);
 70         *bp++ = RTC_CMD_WRITE_DISABLE;
 71 
 72         /* use write-then-read since dma from stack is nonportable */
 73         return spi_write_then_read(spi, buf, sizeof(buf),
 74                         NULL, 0);
 75 }
 76 
 77 static int ds1302_rtc_get_time(struct device *dev, struct rtc_time *time)
 78 {
 79         struct spi_device       *spi = dev_get_drvdata(dev);
 80         u8              addr = RTC_CLCK_BURST << 1 | RTC_CMD_READ;
 81         u8              buf[RTC_CLCK_LEN - 1];
 82         int             status;
 83 
 84         /* Use write-then-read to get all the date/time registers
 85          * since dma from stack is nonportable
 86          */
 87         status = spi_write_then_read(spi, &addr, sizeof(addr),
 88                         buf, sizeof(buf));
 89         if (status < 0)
 90                 return status;
 91 
 92         /* Decode the registers */
 93         time->tm_sec = bcd2bin(buf[RTC_ADDR_SEC]);
 94         time->tm_min = bcd2bin(buf[RTC_ADDR_MIN]);
 95         time->tm_hour = bcd2bin(buf[RTC_ADDR_HOUR]);
 96         time->tm_wday = buf[RTC_ADDR_DAY] - 1;
 97         time->tm_mday = bcd2bin(buf[RTC_ADDR_DATE]);
 98         time->tm_mon = bcd2bin(buf[RTC_ADDR_MON]) - 1;
 99         time->tm_year = bcd2bin(buf[RTC_ADDR_YEAR]) + 100;
100 
101         /* Time may not be set */
102         return rtc_valid_tm(time);
103 }
104 
105 static struct rtc_class_ops ds1302_rtc_ops = {
106         .read_time      = ds1302_rtc_get_time,
107         .set_time       = ds1302_rtc_set_time,
108 };
109 
110 static int ds1302_probe(struct spi_device *spi)
111 {
112         struct rtc_device       *rtc;
113         u8              addr;
114         u8              buf[4];
115         u8              *bp = buf;
116         int             status;
117 
118         /* Sanity check board setup data.  This may be hooked up
119          * in 3wire mode, but we don't care.  Note that unless
120          * there's an inverter in place, this needs SPI_CS_HIGH!
121          */
122         if (spi->bits_per_word && (spi->bits_per_word != 8)) {
123                 dev_err(&spi->dev, "bad word length\n");
124                 return -EINVAL;
125         } else if (spi->max_speed_hz > 2000000) {
126                 dev_err(&spi->dev, "speed is too high\n");
127                 return -EINVAL;
128         } else if (spi->mode & SPI_CPHA) {
129                 dev_err(&spi->dev, "bad mode\n");
130                 return -EINVAL;
131         }
132 
133         addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
134         status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
135         if (status < 0) {
136                 dev_err(&spi->dev, "control register read error %d\n",
137                                 status);
138                 return status;
139         }
140 
141         if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
142                 status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
143                 if (status < 0) {
144                         dev_err(&spi->dev, "control register read error %d\n",
145                                         status);
146                         return status;
147                 }
148 
149                 if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
150                         dev_err(&spi->dev, "junk in control register\n");
151                         return -ENODEV;
152                 }
153         }
154         if (buf[0] == 0) {
155                 bp = buf;
156                 *bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
157                 *bp++ = RTC_CMD_WRITE_DISABLE;
158 
159                 status = spi_write_then_read(spi, buf, 2, NULL, 0);
160                 if (status < 0) {
161                         dev_err(&spi->dev, "control register write error %d\n",
162                                         status);
163                         return status;
164                 }
165 
166                 addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
167                 status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
168                 if (status < 0) {
169                         dev_err(&spi->dev,
170                                         "error %d reading control register\n",
171                                         status);
172                         return status;
173                 }
174 
175                 if (buf[0] != RTC_CMD_WRITE_DISABLE) {
176                         dev_err(&spi->dev, "failed to detect chip\n");
177                         return -ENODEV;
178                 }
179         }
180 
181         spi_set_drvdata(spi, spi);
182 
183         rtc = devm_rtc_device_register(&spi->dev, "ds1302",
184                         &ds1302_rtc_ops, THIS_MODULE);
185         if (IS_ERR(rtc)) {
186                 status = PTR_ERR(rtc);
187                 dev_err(&spi->dev, "error %d registering rtc\n", status);
188                 return status;
189         }
190 
191         return 0;
192 }
193 
194 static int ds1302_remove(struct spi_device *spi)
195 {
196         spi_set_drvdata(spi, NULL);
197         return 0;
198 }
199 
200 #ifdef CONFIG_OF
201 static const struct of_device_id ds1302_dt_ids[] = {
202         { .compatible = "maxim,ds1302", },
203         { /* sentinel */ }
204 };
205 MODULE_DEVICE_TABLE(of, ds1302_dt_ids);
206 #endif
207 
208 static struct spi_driver ds1302_driver = {
209         .driver.name    = "rtc-ds1302",
210         .driver.of_match_table = of_match_ptr(ds1302_dt_ids),
211         .probe          = ds1302_probe,
212         .remove         = ds1302_remove,
213 };
214 
215 module_spi_driver(ds1302_driver);
216 
217 MODULE_DESCRIPTION("Dallas DS1302 RTC driver");
218 MODULE_AUTHOR("Paul Mundt, David McCullough");
219 MODULE_LICENSE("GPL v2");
220 

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