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: 1d1945d261a2af "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>
diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 821d9c0..f25f7dc 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -602,6 +602,8 @@
* 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 @@
{
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 @@
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);