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