[U-Boot] [PATCH 2/2] rtc: pcf2127: Fixed bug with rtc settings and getting error time

[Chuanhua Han]

The previous pcf2127 RTC chip could not read and set the correct time.
When reading the data of internal registers, the read address was the
value of register plus 1. This is because this chip requires the host
to send a stop signal after setting the register address and before
reading the register data.

This patch sets the DM_I2C_CHIP_ADDR_STOP flag in order to
generate a stop signal and fixes the bug of the original read and write
time.

Signed-off-by: Biwen Li <biwen.li at nxp.com>
Signed-off-by: Chuanhua Han <chuanhua.han at nxp.com>
---
Changes in v4:
	- Replace DM_I2C_CHIP_RD_NO_I2C_SETUP_OFFSET with
DM_I2C_CHIP_ADDR_STOP.

Changes in v3:
	- When the rtc time is obtained, the address of the set register
is separated from the read data.

Changes in v2: 
        - Split the original patch into 3 patches
        - Add detailed description information for each patch

 drivers/rtc/pcf2127.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/rtc/pcf2127.c b/drivers/rtc/pcf2127.c
index dcf0340b4d..65794b98e6 100644
--- a/drivers/rtc/pcf2127.c
+++ b/drivers/rtc/pcf2127.c
@@ -24,12 +24,9 @@
 
 static int pcf2127_rtc_set(struct udevice *dev, const struct rtc_time *tm)
 {
-	uchar buf[8];
+	uchar buf[7] = {0};
 	int i = 0, ret;
 
-	/* start register address */
-	buf[i++] = PCF2127_REG_SC;
-
 	/* hours, minutes and seconds */
 	buf[i++] = bin2bcd(tm->tm_sec);
 	buf[i++] = bin2bcd(tm->tm_min);
@@ -44,7 +41,7 @@ static int pcf2127_rtc_set(struct udevice *dev, const struct rtc_time *tm)
 	buf[i++] = bin2bcd(tm->tm_year % 100);
 
 	/* write register's data */
-	ret = dm_i2c_write(dev, PCF2127_REG_CTRL1, buf, sizeof(buf));
+	ret = dm_i2c_write(dev, PCF2127_REG_SC, buf, i);
 
 	return ret;
 }
@@ -54,9 +51,12 @@ static int pcf2127_rtc_get(struct udevice *dev, struct rtc_time *tm)
 	int ret = 0;
 	uchar buf[10] = { PCF2127_REG_CTRL1 };
 
-	ret = dm_i2c_write(dev, PCF2127_REG_CTRL1, buf, 1);
+	/* Set the address of the start register to be read */
+	ret = dm_i2c_write(dev, PCF2127_REG_CTRL1, NULL, 0);
 	if (ret < 0)
 		return ret;
+
+	/* Read register's data */
 	ret = dm_i2c_read(dev, PCF2127_REG_CTRL1, buf, sizeof(buf));
 	if (ret < 0)
 		return ret;
@@ -90,6 +90,13 @@ static int pcf2127_rtc_reset(struct udevice *dev)
 	return 0;
 }
 
+static int pcf2127_probe(struct udevice *dev)
+{
+	i2c_set_chip_flags(dev, DM_I2C_CHIP_ADDR_STOP);
+
+	return 0;
+}
+
 static const struct rtc_ops pcf2127_rtc_ops = {
 	.get = pcf2127_rtc_get,
 	.set = pcf2127_rtc_set,
@@ -104,6 +111,7 @@ static const struct udevice_id pcf2127_rtc_ids[] = {
 U_BOOT_DRIVER(rtc_pcf2127) = {
 	.name	= "rtc-pcf2127",
 	.id	= UCLASS_RTC,
+	.probe	= pcf2127_probe,
 	.of_match = pcf2127_rtc_ids,
 	.ops	= &pcf2127_rtc_ops,
 };
-- 
2.17.1