rtc: pcf85063: fix time/date setting

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>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

1 files changed, 55 insertions, 23 deletions

diff --git a/drivers/rtc/rtc-pcf85063.c b/drivers/rtc/rtc-pcf85063.c
index e0343e6aeb31..c5db231f14de 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;