linux-kernel - [PATCH 1/1] RTC: nuvoton: Modify the setting timing of write ownership

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Date:   Tue, 18 Jul 2023 16:45:35 +0800
From:   Mia Lin <mimi05633@...il.com>
To:     avifishman70@...il.com, tmaimon77@...il.com, tali.perry1@...il.com,
        venture@...gle.com, yuenn@...gle.com, benjaminfair@...gle.com,
        a.zummo@...ertech.it, alexandre.belloni@...tlin.com,
        KWLIU@...oton.com, JJLIU0@...oton.com, KFLIN@...oton.com,
        YHYANG2@...oton.com, mylin1@...oton.com
Cc:     openbmc@...ts.ozlabs.org, linux-rtc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mia Lin <mimi05633@...il.com>
Subject: [PATCH 1/1] RTC: nuvoton: Modify the setting timing of write ownership

- Change the write ownership to default.
- Set the TWO bit to gain write ownership for BMC before it updates time.
- Restore the TWO bit after BMC updates the time.
- Set 24-Hour Format.

Signed-off-by: Mia Lin <mimi05633@...il.com>
---
 drivers/rtc/rtc-nct3018y.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-nct3018y.c b/drivers/rtc/rtc-nct3018y.c
index a4e3f924837e..e6b06724cdef 100644
--- a/drivers/rtc/rtc-nct3018y.c
+++ b/drivers/rtc/rtc-nct3018y.c
@@ -178,7 +178,19 @@ static int nct3018y_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	unsigned char buf[4] = {0};
-	int err;
+	int err, flags, restore_flags = 0;
+
+	/* Check and set TWO bit */
+	flags = i2c_smbus_read_byte_data(client, NCT3018Y_REG_CTRL);
+	if (!(flags & NCT3018Y_BIT_TWO)) {
+		restore_flags = 1;
+		flags |= NCT3018Y_BIT_TWO;
+		err = i2c_smbus_write_byte_data(client, NCT3018Y_REG_CTRL, flags);
+		if (err < 0) {
+			dev_dbg(&client->dev, "Unable to write NCT3018Y_REG_CTRL\n");
+			return err;
+		}
+	}
 
 	buf[0] = bin2bcd(tm->tm_sec);
 	err = i2c_smbus_write_byte_data(client, NCT3018Y_REG_SC, buf[0]);
@@ -212,6 +224,16 @@ static int nct3018y_rtc_set_time(struct device *dev, struct rtc_time *tm)
 		return -EIO;
 	}
 
+	/* Restore TWO bit */
+	if (restore_flags) {
+		flags &= ~NCT3018Y_BIT_TWO;
+		err = i2c_smbus_write_byte_data(client, NCT3018Y_REG_CTRL, flags);
+		if (err < 0) {
+			dev_dbg(&client->dev, "Unable to write NCT3018Y_REG_CTRL\n");
+			return err;
+		}
+	}
+
 	return err;
 }
 
@@ -479,7 +501,7 @@ static int nct3018y_probe(struct i2c_client *client)
 		dev_dbg(&client->dev, "%s: NCT3018Y_BIT_TWO is set\n", __func__);
 	}
 
-	flags = NCT3018Y_BIT_TWO;
+	flags = NCT3018Y_BIT_HF;
 	err = i2c_smbus_write_byte_data(client, NCT3018Y_REG_CTRL, flags);
 	if (err < 0) {
 		dev_dbg(&client->dev, "Unable to write NCT3018Y_REG_CTRL\n");
-- 
2.17.1