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Commit e29385fa authored by Keerthy's avatar Keerthy Committed by Alexandre Belloni
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rtc: ds1307: Fix relying on reset value for weekday 

The reset value of weekday is 0x1. This is wrong since
the reset values of the day/month/year make up to Jan 1 2001.
When computed weekday comes out to be Monday. On a scale
of 1-7(Sunday - Saturday) it should be 0x2. So we should not
be relying on the reset value.

Hence compute the wday using the current date/month/year values.
Check if reset wday is any different from the computed wday,
If different then set the wday which we computed using
date/month/year values.

Document Referred:
http://ww1.microchip.com/downloads/en/DeviceDoc/20002266F.pdf



Fixes: 1d1945d2 "drivers/rtc/rtc-ds1307.c: add alarm support for mcp7941x chips"
Signed-off-by: default avatarKeerthy <j-keerthy@ti.com>
Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@free-electrons.com>
parent cd9b518b

drivers/rtc/rtc-ds1307.c

+27 −1
Original line number Diff line number Diff line
@@ -602,6 +602,8 @@ static const struct rtc_class_ops ds13xx_rtc_ops = { 
 * Alarm support for mcp794xx devices.

 */



#define MCP794XX_REG_WEEKDAY		0x3

#define MCP794XX_REG_WEEKDAY_WDAY_MASK	0x7

#define MCP794XX_REG_CONTROL		0x07

#	define MCP794XX_BIT_ALM0_EN	0x10

#	define MCP794XX_BIT_ALM1_EN	0x20
@@ -1231,13 +1233,16 @@ static int ds1307_probe(struct i2c_client *client, 
{

	struct ds1307		*ds1307;

	int			err = -ENODEV;

	int			tmp;

	int			tmp, wday;

	struct chip_desc	*chip = &chips[id->driver_data];

	struct i2c_adapter	*adapter = to_i2c_adapter(client->dev.parent);

	bool			want_irq = false;

	bool			ds1307_can_wakeup_device = false;

	unsigned char		*buf;

	struct ds1307_platform_data *pdata = dev_get_platdata(&client->dev);

	struct rtc_time		tm;

	unsigned long		timestamp;



	irq_handler_t	irq_handler = ds1307_irq;



	static const int	bbsqi_bitpos[] = {
@@ -1526,6 +1531,27 @@ static int ds1307_probe(struct i2c_client *client, 
				bin2bcd(tmp));

	}



	/*

	 * Some IPs have weekday reset value = 0x1 which might not correct

	 * hence compute the wday using the current date/month/year values

	 */

	ds1307_get_time(&client->dev, &tm);

	wday = tm.tm_wday;

	timestamp = rtc_tm_to_time64(&tm);

	rtc_time64_to_tm(timestamp, &tm);



	/*

	 * Check if reset wday is different from the computed wday

	 * If different then set the wday which we computed using

	 * timestamp

	 */

	if (wday != tm.tm_wday) {

		wday = i2c_smbus_read_byte_data(client, MCP794XX_REG_WEEKDAY);

		wday = wday & ~MCP794XX_REG_WEEKDAY_WDAY_MASK;

		wday = wday | (tm.tm_wday + 1);

		i2c_smbus_write_byte_data(client, MCP794XX_REG_WEEKDAY, wday);

	}



	if (want_irq) {

		device_set_wakeup_capable(&client->dev, true);

		set_bit(HAS_ALARM, &ds1307->flags);