diff options
Diffstat (limited to 'drivers/rtc/rtc-mcp795.c')
| -rw-r--r-- | drivers/rtc/rtc-mcp795.c | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-mcp795.c b/drivers/rtc/rtc-mcp795.c new file mode 100644 index 00000000000..34295bf0041 --- /dev/null +++ b/drivers/rtc/rtc-mcp795.c @@ -0,0 +1,199 @@ +/* + * 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"); |