linux/drivers/rtc/rtc-pcf85063.c

// SPDX-License-Identifier: GPL-2.0
/*
 * An I2C driver for the PCF85063 RTC
 * Copyright 2014 Rose Technology
 *
 * Author: Søren Andersen <san@rosetechnology.dk>
 * Maintainers: http://www.nslu2-linux.org/
 */
#include <linux/i2c.h>
#include <linux/bcd.h>
#include <linux/rtc.h>
#include <linux/module.h>

/*
 * Information for this driver was pulled from the following datasheets.
 *
 *  http://www.nxp.com/documents/data_sheet/PCF85063A.pdf
 *  http://www.nxp.com/documents/data_sheet/PCF85063TP.pdf
 *
 *  PCF85063A -- Rev. 6 — 18 November 2015
 *  PCF85063TP -- Rev. 4 — 6 May 2015
*/

#define PCF85063_REG_CTRL1		0x00 /* status */
#define PCF85063_REG_CTRL1_CAP_SEL	BIT(0)
#define PCF85063_REG_CTRL1_STOP		BIT(5)

#define PCF85063_REG_SC			0x04 /* datetime */
#define PCF85063_REG_SC_OS		0x80

static int pcf85063_stop_clock(struct i2c_client *client, u8 *ctrl1)
{
	int rc;
	u8 reg;

	rc = i2c_smbus_read_byte_data(client, PCF85063_REG_CTRL1);
	if (rc < 0) {
		dev_err(&client->dev, "Failing to stop the clock\n");
		return -EIO;
	}

	/* stop the clock */
	reg = rc | PCF85063_REG_CTRL1_STOP;

	rc = i2c_smbus_write_byte_data(client, PCF85063_REG_CTRL1, reg);
	if (rc < 0) {
		dev_err(&client->dev, "Failing to stop the clock\n");
		return -EIO;
	}

	*ctrl1 = reg;

	return 0;
}

static int pcf85063_start_clock(struct i2c_client *client, u8 ctrl1)
{
	int rc;

	/* start the clock */
	ctrl1 &= ~PCF85063_REG_CTRL1_STOP;

	rc = i2c_smbus_write_byte_data(client, PCF85063_REG_CTRL1, ctrl1);
	if (rc < 0) {
		dev_err(&client->dev, "Failing to start the clock\n");
		return -EIO;
	}

	return 0;
}

static int pcf85063_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	struct i2c_client *client = to_i2c_client(dev);
	int rc;
	u8 regs[7];

	/*
	 * while reading, the time/date registers are blocked and not updated
	 * anymore until the access is finished. To not lose a second
	 * event, the access must be finished within one second. So, read all
	 * time/date registers in one turn.
	 */
	rc = i2c_smbus_read_i2c_block_data(client, PCF85063_REG_SC,
					   sizeof(regs), regs);
	if (rc != sizeof(regs)) {
		dev_err(&client->dev, "date/time register read error\n");
		return -EIO;
	}

	/* if the clock has lost its power it makes no sense to use its time */
	if (regs[0] & PCF85063_REG_SC_OS) {
		dev_warn(&client->dev, "Power loss detected, invalid time\n");
		return -EINVAL;
	}

	tm->tm_sec = bcd2bin(regs[0] & 0x7F);
	tm->tm_min = bcd2bin(regs[1] & 0x7F);
	tm->tm_hour = bcd2bin(regs[2] & 0x3F); /* rtc hr 0-23 */
	tm->tm_mday = bcd2bin(regs[3] & 0x3F);
	tm->tm_wday = regs[4] & 0x07;
	tm->tm_mon = bcd2bin(regs[5] & 0x1F) - 1; /* rtc mn 1-12 */
	tm->tm_year = bcd2bin(regs[6]);
	tm->tm_year += 100;

	return 0;
}

static int pcf85063_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	struct i2c_client *client = to_i2c_client(dev);
	int rc;
	u8 regs[7];
	u8 ctrl1;

	/*
	 * to accurately set the time, reset the divider chain and keep it in
	 * reset state until all time/date registers are written
	 */
	rc = pcf85063_stop_clock(client, &ctrl1);
	if (rc != 0)
		return rc;

	/* hours, minutes and seconds */
	regs[0] = bin2bcd(tm->tm_sec) & 0x7F; /* clear OS flag */

	regs[1] = bin2bcd(tm->tm_min);
	regs[2] = bin2bcd(tm->tm_hour);

	/* Day of month, 1 - 31 */
	regs[3] = bin2bcd(tm->tm_mday);

	/* Day, 0 - 6 */
	regs[4] = tm->tm_wday & 0x07;

	/* month, 1 - 12 */
	regs[5] = bin2bcd(tm->tm_mon + 1);

	/* year and century */
	regs[6] = bin2bcd(tm->tm_year - 100);

	/* write all registers at once */
	rc = i2c_smbus_write_i2c_block_data(client, PCF85063_REG_SC,
					    sizeof(regs), regs);
	if (rc < 0) {
		dev_err(&client->dev, "date/time register write error\n");
		return rc;
	}

	/*
	 * Write the control register as a separate action since the size of
	 * the register space is different between the PCF85063TP and
	 * PCF85063A devices.  The rollover point can not be used.
	 */
	rc = pcf85063_start_clock(client, ctrl1);
	if (rc != 0)
		return rc;

	return 0;
}

static const struct rtc_class_ops pcf85063_rtc_ops = {
	.read_time	= pcf85063_rtc_read_time,
	.set_time	= pcf85063_rtc_set_time
};

static int pcf85063_load_capacitance(struct i2c_client *client)
{
	u32 load;
	int rc;
	u8 reg;

	rc = i2c_smbus_read_byte_data(client, PCF85063_REG_CTRL1);
	if (rc < 0)
		return rc;

	reg = rc;
	load = 7000;
	of_property_read_u32(client->dev.of_node, "quartz-load-femtofarads",
			     &load);

	switch (load) {
	default:
		dev_warn(&client->dev, "Unknown quartz-load-femtofarads value: %d. Assuming 7000",
			 load);
		/* fall through */
	case 7000:
		reg &= ~PCF85063_REG_CTRL1_CAP_SEL;
		break;
	case 12500:
		reg |= PCF85063_REG_CTRL1_CAP_SEL;
		break;
	}

	rc = i2c_smbus_write_byte_data(client, PCF85063_REG_CTRL1, reg);

	return rc;
}

static int pcf85063_probe(struct i2c_client *client)
{
	struct rtc_device *rtc;
	int err;

	dev_dbg(&client->dev, "%s\n", __func__);

	err = i2c_smbus_read_byte_data(client, PCF85063_REG_CTRL1);
	if (err < 0) {
		dev_err(&client->dev, "RTC chip is not present\n");
		return err;
	}

	err = pcf85063_load_capacitance(client);
	if (err < 0)
		dev_warn(&client->dev, "failed to set xtal load capacitance: %d",
			 err);

	rtc = devm_rtc_allocate_device(&client->dev);
	if (IS_ERR(rtc))
		return PTR_ERR(rtc);

	rtc->ops = &pcf85063_rtc_ops;
	rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
	rtc->range_max = RTC_TIMESTAMP_END_2099;

	return rtc_register_device(rtc);
}

#ifdef CONFIG_OF
static const struct of_device_id pcf85063_of_match[] = {
	{ .compatible = "nxp,pcf85063" },
	{}
};
MODULE_DEVICE_TABLE(of, pcf85063_of_match);
#endif

static struct i2c_driver pcf85063_driver = {
	.driver		= {
		.name	= "rtc-pcf85063",
		.of_match_table = of_match_ptr(pcf85063_of_match),
	},
	.probe_new	= pcf85063_probe,
};

module_i2c_driver(pcf85063_driver);

MODULE_AUTHOR("Søren Andersen <san@rosetechnology.dk>");
MODULE_DESCRIPTION("PCF85063 RTC driver");
MODULE_LICENSE("GPL");