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 }, 190 .probe = mcp795_probe, 191 }; 192 193 module_spi_driver(mcp795_driver); 194 195 MODULE_DESCRIPTION("MCP795 RTC SPI Driver"); 196 MODULE_AUTHOR("Josef Gajdusek <atx@atx.name>"); 197 MODULE_LICENSE("GPL"); 198 MODULE_ALIAS("spi:mcp795"); 199