/* * SPI Driver for Microchip MCP795 RTC * * Copyright (C) Josef Gajdusek <atx@atx.name> * * based on other Linux RTC drivers * * Device datasheet: * http://ww1.microchip.com/downloads/en/DeviceDoc/22280A.pdf * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * * */ #include <linux/module.h> #include <linux/kernel.h> #include <linux/device.h> #include <linux/printk.h> #include <linux/spi/spi.h> #include <linux/rtc.h> /* MCP795 Instructions, see datasheet table 3-1 */ #define MCP795_EEREAD 0x03 #define MCP795_EEWRITE 0x02 #define MCP795_EEWRDI 0x04 #define MCP795_EEWREN 0x06 #define MCP795_SRREAD 0x05 #define MCP795_SRWRITE 0x01 #define MCP795_READ 0x13 #define MCP795_WRITE 0x12 #define MCP795_UNLOCK 0x14 #define MCP795_IDWRITE 0x32 #define MCP795_IDREAD 0x33 #define MCP795_CLRWDT 0x44 #define MCP795_CLRRAM 0x54 #define MCP795_ST_BIT 0x80 #define MCP795_24_BIT 0x40 static int mcp795_rtcc_read(struct device *dev, u8 addr, u8 *buf, u8 count) { struct spi_device *spi = to_spi_device(dev); int ret; u8 tx[2]; tx[0] = MCP795_READ; tx[1] = addr; ret = spi_write_then_read(spi, tx, sizeof(tx), buf, count); if (ret) dev_err(dev, "Failed reading %d bytes from address %x.\n", count, addr); return ret; } static int mcp795_rtcc_write(struct device *dev, u8 addr, u8 *data, u8 count) { struct spi_device *spi = to_spi_device(dev); int ret; u8 tx[2 + count]; tx[0] = MCP795_WRITE; tx[1] = addr; memcpy(&tx[2], data, count); ret = spi_write(spi, tx, 2 + count); if (ret) dev_err(dev, "Failed to write %d bytes to address %x.\n", count, addr); return ret; } static int mcp795_rtcc_set_bits(struct device *dev, u8 addr, u8 mask, u8 state) { int ret; u8 tmp; ret = mcp795_rtcc_read(dev, addr, &tmp, 1); if (ret) return ret; if ((tmp & mask) != state) { tmp = (tmp & ~mask) | state; ret = mcp795_rtcc_write(dev, addr, &tmp, 1); } return ret; } static int mcp795_set_time(struct device *dev, struct rtc_time *tim) { int ret; u8 data[7]; /* Read first, so we can leave config bits untouched */ ret = mcp795_rtcc_read(dev, 0x01, data, sizeof(data)); if (ret) return ret; data[0] = (data[0] & 0x80) | ((tim->tm_sec / 10) << 4) | (tim->tm_sec % 10); data[1] = (data[1] & 0x80) | ((tim->tm_min / 10) << 4) | (tim->tm_min % 10); data[2] = ((tim->tm_hour / 10) << 4) | (tim->tm_hour % 10); data[4] = ((tim->tm_mday / 10) << 4) | ((tim->tm_mday) % 10); data[5] = (data[5] & 0x10) | (tim->tm_mon / 10) | (tim->tm_mon % 10); if (tim->tm_year > 100) tim->tm_year -= 100; data[6] = ((tim->tm_year / 10) << 4) | (tim->tm_year % 10); ret = mcp795_rtcc_write(dev, 0x01, data, sizeof(data)); if (ret) return ret; dev_dbg(dev, "Set mcp795: %04d-%02d-%02d %02d:%02d:%02d\n", tim->tm_year + 1900, tim->tm_mon, tim->tm_mday, tim->tm_hour, tim->tm_min, tim->tm_sec); return 0; } static int mcp795_read_time(struct device *dev, struct rtc_time *tim) { int ret; u8 data[7]; ret = mcp795_rtcc_read(dev, 0x01, data, sizeof(data)); if (ret) return ret; tim->tm_sec = ((data[0] & 0x70) >> 4) * 10 + (data[0] & 0x0f); tim->tm_min = ((data[1] & 0x70) >> 4) * 10 + (data[1] & 0x0f); tim->tm_hour = ((data[2] & 0x30) >> 4) * 10 + (data[2] & 0x0f); tim->tm_mday = ((data[4] & 0x30) >> 4) * 10 + (data[4] & 0x0f); tim->tm_mon = ((data[5] & 0x10) >> 4) * 10 + (data[5] & 0x0f); tim->tm_year = ((data[6] & 0xf0) >> 4) * 10 + (data[6] & 0x0f) + 100; /* Assume we are in 20xx */ dev_dbg(dev, "Read from mcp795: %04d-%02d-%02d %02d:%02d:%02d\n", tim->tm_year + 1900, tim->tm_mon, tim->tm_mday, tim->tm_hour, tim->tm_min, tim->tm_sec); return rtc_valid_tm(tim); } static struct rtc_class_ops mcp795_rtc_ops = { .read_time = mcp795_read_time, .set_time = mcp795_set_time }; static int mcp795_probe(struct spi_device *spi) { struct rtc_device *rtc; int ret; spi->mode = SPI_MODE_0; spi->bits_per_word = 8; ret = spi_setup(spi); if (ret) { dev_err(&spi->dev, "Unable to setup SPI\n"); return ret; } /* Start the oscillator */ mcp795_rtcc_set_bits(&spi->dev, 0x01, MCP795_ST_BIT, MCP795_ST_BIT); /* Clear the 12 hour mode flag*/ mcp795_rtcc_set_bits(&spi->dev, 0x03, MCP795_24_BIT, 0); rtc = devm_rtc_device_register(&spi->dev, "rtc-mcp795", &mcp795_rtc_ops, THIS_MODULE); if (IS_ERR(rtc)) return PTR_ERR(rtc); spi_set_drvdata(spi, rtc); return 0; } static struct spi_driver mcp795_driver = { .driver = { .name = "rtc-mcp795", .owner = THIS_MODULE, }, .probe = mcp795_probe, }; module_spi_driver(mcp795_driver); MODULE_DESCRIPTION("MCP795 RTC SPI Driver"); MODULE_AUTHOR("Josef Gajdusek <atx@atx.name>"); MODULE_LICENSE("GPL"); MODULE_ALIAS("spi:mcp795");