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Subject[PATCH v2 3/3] RTC/PCF85063: fix time/date setting
Date
When setting a new time/date the RTC's clock must be stopped first, in
order to write the time/date registers in an atomic manner.
So, this change stops the clock first and then writes the time/date
registers and the clock control register (to re-enable the clock) in one
turn.

Signed-off-by: Juergen Borleis <jbe@pengutronix.de>
---
drivers/rtc/rtc-pcf85063.c | 78 ++++++++++++++++++++++++++++++++--------------
1 file changed, 55 insertions(+), 23 deletions(-)

diff --git a/drivers/rtc/rtc-pcf85063.c b/drivers/rtc/rtc-pcf85063.c
index e0343e6..c5db231 100644
--- a/drivers/rtc/rtc-pcf85063.c
+++ b/drivers/rtc/rtc-pcf85063.c
@@ -19,6 +19,7 @@
#define DRV_VERSION "0.0.1"

#define PCF85063_REG_CTRL1 0x00 /* status */
+#define PCF85063_REG_CTRL1_STOP BIT(5)
#define PCF85063_REG_CTRL2 0x01

#define PCF85063_REG_SC 0x04 /* datetime */
@@ -40,6 +41,30 @@ struct pcf85063 {
int voltage_low; /* indicates if a low_voltage was detected */
};

+static int pcf85063_stop_clock(struct i2c_client *client, u8 *ctrl1)
+{
+ s32 ret;
+
+ ret = i2c_smbus_read_byte_data(client, PCF85063_REG_CTRL1);
+ if (ret < 0) {
+ dev_err(&client->dev, "Failing to stop the clock\n");
+ return -EIO;
+ }
+
+ /* stop the clock */
+ ret |= PCF85063_REG_CTRL1_STOP;
+
+ ret = i2c_smbus_write_byte_data(client, PCF85063_REG_CTRL1, ret);
+ if (ret < 0) {
+ dev_err(&client->dev, "Failing to stop the clock\n");
+ return -EIO;
+ }
+
+ *ctrl1 = ret;
+
+ return 0;
+}
+
/*
* In the routines that deal directly with the pcf85063 hardware, we use
* rtc_time -- month 0-11, hour 0-23, yr = calendar year-epoch.
@@ -87,41 +112,48 @@ static int pcf85063_get_datetime(struct i2c_client *client, struct rtc_time *tm)

static int pcf85063_set_datetime(struct i2c_client *client, struct rtc_time *tm)
{
- int i = 0, err = 0;
- unsigned char buf[11];
+ int rc;
+ u8 regs[8];

- /* Control & status */
- buf[PCF85063_REG_CTRL1] = 0;
- buf[PCF85063_REG_CTRL2] = 5;
+ /*
+ * 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, &regs[7]);
+ if (rc != 0)
+ return rc;

/* hours, minutes and seconds */
- buf[PCF85063_REG_SC] = bin2bcd(tm->tm_sec) & 0x7F;
+ regs[0] = bin2bcd(tm->tm_sec) & 0x7F; /* clear OS flag */

- buf[PCF85063_REG_MN] = bin2bcd(tm->tm_min);
- buf[PCF85063_REG_HR] = bin2bcd(tm->tm_hour);
+ regs[1] = bin2bcd(tm->tm_min);
+ regs[2] = bin2bcd(tm->tm_hour);

/* Day of month, 1 - 31 */
- buf[PCF85063_REG_DM] = bin2bcd(tm->tm_mday);
+ regs[3] = bin2bcd(tm->tm_mday);

/* Day, 0 - 6 */
- buf[PCF85063_REG_DW] = tm->tm_wday & 0x07;
+ regs[4] = tm->tm_wday & 0x07;

/* month, 1 - 12 */
- buf[PCF85063_REG_MO] = bin2bcd(tm->tm_mon + 1);
+ regs[5] = bin2bcd(tm->tm_mon + 1);

/* year and century */
- buf[PCF85063_REG_YR] = bin2bcd(tm->tm_year % 100);
-
- /* write register's data */
- for (i = 0; i < sizeof(buf); i++) {
- unsigned char data[2] = { i, buf[i] };
-
- err = i2c_master_send(client, data, sizeof(data));
- if (err != sizeof(data)) {
- dev_err(&client->dev, "%s: err=%d addr=%02x, data=%02x\n",
- __func__, err, data[0], data[1]);
- return -EIO;
- }
+ regs[6] = bin2bcd(tm->tm_year % 100);
+
+ /*
+ * after all time/date registers are written, let the 'address auto
+ * increment' feature wrap around and write register CTRL1 to re-enable
+ * the clock divider chain again
+ */
+ regs[7] &= ~PCF85063_REG_CTRL1_STOP;
+
+ /* 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;
}

return 0;
--
2.7.0.rc3
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