This is a note to let you know that I've just added the patch titled
rtc: ds1307: Fix relying on reset value for weekday
to the 4.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rtc-ds1307-fix-relying-on-reset-value-for-weekday.patch
and it can be found in the queue-4.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e29385fab0bf94017fac130ee32f5bb2daf74417 Mon Sep 17 00:00:00 2001
From: Keerthy <j-keerthy@xxxxxx>
Date: Wed, 1 Jun 2016 16:19:07 +0530
Subject: rtc: ds1307: Fix relying on reset value for weekday
From: Keerthy <j-keerthy@xxxxxx>
commit e29385fab0bf94017fac130ee32f5bb2daf74417 upstream.
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@xxxxxx>
Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/rtc/rtc-ds1307.c | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -602,6 +602,8 @@ static const struct rtc_class_ops ds13xx
* 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_clien
{
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 @@ read_rtc:
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);
Patches currently in stable-queue which might be from j-keerthy@xxxxxx are
queue-4.7/rtc-ds1307-fix-relying-on-reset-value-for-weekday.patch
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