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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: 1d1945d261 "drivers/rtc/rtc-ds1307.c: add alarm support for mcp7941x chips"
Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
This commit is contained in:
Keerthy 2016-06-01 16:19:07 +05:30 committed by Alexandre Belloni
parent cd9b518b98
commit e29385fab0
1 changed files with 27 additions and 1 deletions
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28
drivers/rtc/rtc-ds1307.c
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@ -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);