drivers/rtc/rtc-mcp795.c

   1 /*
   2  * SPI Driver for Microchip MCP795 RTC
   3  *
   4  * Copyright (C) Josef Gajdusek <atx@atx.name>
   5  *
   6  * based on other Linux RTC drivers
   7  *
   8  * Device datasheet:
   9  * http://ww1.microchip.com/downloads/en/DeviceDoc/22280A.pdf
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License version 2 as
  13  * published by the Free Software Foundation.
  14  *
  15  * */
  16
  17 #include <linux/module.h>
  18 #include <linux/kernel.h>
  19 #include <linux/device.h>
  20 #include <linux/printk.h>
  21 #include <linux/spi/spi.h>
  22 #include <linux/rtc.h>
  23 #include <linux/of.h>
  24
  25 /* MCP795 Instructions, see datasheet table 3-1 */
  26 #define MCP795_EEREAD   0x03
  27 #define MCP795_EEWRITE  0x02
  28 #define MCP795_EEWRDI   0x04
  29 #define MCP795_EEWREN   0x06
  30 #define MCP795_SRREAD   0x05
  31 #define MCP795_SRWRITE  0x01
  32 #define MCP795_READ             0x13
  33 #define MCP795_WRITE    0x12
  34 #define MCP795_UNLOCK   0x14
  35 #define MCP795_IDWRITE  0x32
  36 #define MCP795_IDREAD   0x33
  37 #define MCP795_CLRWDT   0x44
  38 #define MCP795_CLRRAM   0x54
  39
  40 #define MCP795_ST_BIT   0x80
  41 #define MCP795_24_BIT   0x40
  42
  43 static int mcp795_rtcc_read(struct device *dev, u8 addr, u8 *buf, u8 count)
  44 {
  45         struct spi_device *spi = to_spi_device(dev);
  46         int ret;
  47         u8 tx[2];
  48
  49         tx[0] = MCP795_READ;
  50         tx[1] = addr;
  51         ret = spi_write_then_read(spi, tx, sizeof(tx), buf, count);
  52
  53         if (ret)
  54                 dev_err(dev, "Failed reading %d bytes from address %x.\n",
  55                                         count, addr);
  56
  57         return ret;
  58 }
  59
  60 static int mcp795_rtcc_write(struct device *dev, u8 addr, u8 *data, u8 count)
  61 {
  62         struct spi_device *spi = to_spi_device(dev);
  63         int ret;
  64         u8 tx[2 + count];
  65
  66         tx[0] = MCP795_WRITE;
  67         tx[1] = addr;
  68         memcpy(&tx[2], data, count);
  69
  70         ret = spi_write(spi, tx, 2 + count);
  71
  72         if (ret)
  73                 dev_err(dev, "Failed to write %d bytes to address %x.\n",
  74                                         count, addr);
  75
  76         return ret;
  77 }
  78
  79 static int mcp795_rtcc_set_bits(struct device *dev, u8 addr, u8 mask, u8 state)
  80 {
  81         int ret;
  82         u8 tmp;
  83
  84         ret = mcp795_rtcc_read(dev, addr, &tmp, 1);
  85         if (ret)
  86                 return ret;
  87
  88         if ((tmp & mask) != state) {
  89                 tmp = (tmp & ~mask) | state;
  90                 ret = mcp795_rtcc_write(dev, addr, &tmp, 1);
  91         }
  92
  93         return ret;
  94 }
  95
  96 static int mcp795_set_time(struct device *dev, struct rtc_time *tim)
  97 {
  98         int ret;
  99         u8 data[7];
 100
 101         /* Read first, so we can leave config bits untouched */
 102         ret = mcp795_rtcc_read(dev, 0x01, data, sizeof(data));
 103
 104         if (ret)
 105                 return ret;
 106
 107         data[0] = (data[0] & 0x80) | ((tim->tm_sec / 10) << 4) | (tim->tm_sec % 10);
 108         data[1] = (data[1] & 0x80) | ((tim->tm_min / 10) << 4) | (tim->tm_min % 10);
 109         data[2] = ((tim->tm_hour / 10) << 4) | (tim->tm_hour % 10);
 110         data[4] = ((tim->tm_mday / 10) << 4) | ((tim->tm_mday) % 10);
 111         data[5] = (data[5] & 0x10) | (tim->tm_mon / 10) | (tim->tm_mon % 10);
 112
 113         if (tim->tm_year > 100)
 114                 tim->tm_year -= 100;
 115
 116         data[6] = ((tim->tm_year / 10) << 4) | (tim->tm_year % 10);
 117
 118         ret = mcp795_rtcc_write(dev, 0x01, data, sizeof(data));
 119
 120         if (ret)
 121                 return ret;
 122
 123         dev_dbg(dev, "Set mcp795: %04d-%02d-%02d %02d:%02d:%02d\n",
 124                         tim->tm_year + 1900, tim->tm_mon, tim->tm_mday,
 125                         tim->tm_hour, tim->tm_min, tim->tm_sec);
 126
 127         return 0;
 128 }
 129
 130 static int mcp795_read_time(struct device *dev, struct rtc_time *tim)
 131 {
 132         int ret;
 133         u8 data[7];
 134
 135         ret = mcp795_rtcc_read(dev, 0x01, data, sizeof(data));
 136
 137         if (ret)
 138                 return ret;
 139
 140         tim->tm_sec             = ((data[0] & 0x70) >> 4) * 10 + (data[0] & 0x0f);
 141         tim->tm_min             = ((data[1] & 0x70) >> 4) * 10 + (data[1] & 0x0f);
 142         tim->tm_hour    = ((data[2] & 0x30) >> 4) * 10 + (data[2] & 0x0f);
 143         tim->tm_mday    = ((data[4] & 0x30) >> 4) * 10 + (data[4] & 0x0f);
 144         tim->tm_mon             = ((data[5] & 0x10) >> 4) * 10 + (data[5] & 0x0f);
 145         tim->tm_year    = ((data[6] & 0xf0) >> 4) * 10 + (data[6] & 0x0f) + 100; /* Assume we are in 20xx */
 146
 147         dev_dbg(dev, "Read from mcp795: %04d-%02d-%02d %02d:%02d:%02d\n",
 148                                 tim->tm_year + 1900, tim->tm_mon, tim->tm_mday,
 149                                 tim->tm_hour, tim->tm_min, tim->tm_sec);
 150
 151         return rtc_valid_tm(tim);
 152 }
 153
 154 static struct rtc_class_ops mcp795_rtc_ops = {
 155                 .read_time = mcp795_read_time,
 156                 .set_time = mcp795_set_time
 157 };
 158
 159 static int mcp795_probe(struct spi_device *spi)
 160 {
 161         struct rtc_device *rtc;
 162         int ret;
 163
 164         spi->mode = SPI_MODE_0;
 165         spi->bits_per_word = 8;
 166         ret = spi_setup(spi);
 167         if (ret) {
 168                 dev_err(&spi->dev, "Unable to setup SPI\n");
 169                 return ret;
 170         }
 171
 172         /* Start the oscillator */
 173         mcp795_rtcc_set_bits(&spi->dev, 0x01, MCP795_ST_BIT, MCP795_ST_BIT);
 174         /* Clear the 12 hour mode flag*/
 175         mcp795_rtcc_set_bits(&spi->dev, 0x03, MCP795_24_BIT, 0);
 176
 177         rtc = devm_rtc_device_register(&spi->dev, "rtc-mcp795",
 178                                                                 &mcp795_rtc_ops, THIS_MODULE);
 179         if (IS_ERR(rtc))
 180                 return PTR_ERR(rtc);
 181
 182         spi_set_drvdata(spi, rtc);
 183
 184         return 0;
 185 }
 186
 187 #ifdef CONFIG_OF
 188 static const struct of_device_id mcp795_of_match[] = {
 189         { .compatible = "maxim,mcp795" },
 190         { }
 191 };
 192 MODULE_DEVICE_TABLE(of, mcp795_of_match);
 193 #endif
 194
 195 static struct spi_driver mcp795_driver = {
 196                 .driver = {
 197                                 .name = "rtc-mcp795",
 198                                 .of_match_table = of_match_ptr(mcp795_of_match),
 199                 },
 200                 .probe = mcp795_probe,
 201 };
 202
 203 module_spi_driver(mcp795_driver);
 204
 205 MODULE_DESCRIPTION("MCP795 RTC SPI Driver");
 206 MODULE_AUTHOR("Josef Gajdusek <atx@atx.name>");
 207 MODULE_LICENSE("GPL");
 208 MODULE_ALIAS("spi:mcp795");