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Commit 1fcbe42c authored by Josef Gajdusek's avatar Josef Gajdusek Committed by Linus Torvalds
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drivers/rtc: add support for Microchip MCP795 



Add driver for SPI RTC Microchip MCP795.  Only supports saving/loading
time from the chip (i.  e.  no alarms/power events/ID).

Signed-off-by: default avatarJosef Gajdusek <atx@atx.name>
Cc: Jingoo Han <jg1.han@samsung.com>
Acked-by: default avatarAlessandro Zummo <a.zummo@towertech.it>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 10b06b87

drivers/rtc/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -661,6 +661,14 @@ config RTC_DRV_RX4581 
	  This driver can also be built as a module. If so the module

	  will be called rtc-rx4581.



config RTC_DRV_MCP795

	tristate "Microchip MCP795"

	help

	  If you say yes here you will get support for the Microchip MCP795.



	  This driver can also be built as a module. If so the module

	  will be called rtc-mcp795.



endif # SPI_MASTER



comment "Platform RTC drivers"

drivers/rtc/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -81,6 +81,7 @@ obj-$(CONFIG_RTC_DRV_MAX8997) += rtc-max8997.o 
obj-$(CONFIG_RTC_DRV_MAX6902)	+= rtc-max6902.o

obj-$(CONFIG_RTC_DRV_MAX77686)	+= rtc-max77686.o

obj-$(CONFIG_RTC_DRV_MC13XXX)	+= rtc-mc13xxx.o

obj-$(CONFIG_RTC_DRV_MCP795)	+= rtc-mcp795.o

obj-$(CONFIG_RTC_DRV_MSM6242)	+= rtc-msm6242.o

obj-$(CONFIG_RTC_DRV_MPC5121)	+= rtc-mpc5121.o

obj-$(CONFIG_RTC_DRV_MV)	+= rtc-mv.o

drivers/rtc/rtc-mcp795.c

0 → 100644
+199 −0
Original line number Diff line number Diff line 
/*

 * 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");