[v2,2/2] rtc: hym8563: Read the valid flag directly instead of caching it
diff mbox series

Message ID 20191212153111.966923-2-paul.kocialkowski@bootlin.com
State Accepted
Headers show
Series
  • [v2,1/2] rtc: hym8563: Return -EINVAL if the time is known to be invalid
Related show

Commit Message

Paul Kocialkowski Dec. 12, 2019, 3:31 p.m. UTC
The RTC has a valid bit in the seconds register that indicates whether
power was lost since the pevious time set. This bit is currently read
once at probe time, cached and updated with set_time.

Howeever, caching the bit may prevent detecting power loss at runtime
(which can happen if the RTC's supply is distinct from the the platform's).

Writing the seconds register when setting time will clear the bit,
so there should be no downside in reading the bit directly instead of
caching it.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
---
Changes since v1:
- Removed hym8563 unused variables;
- Checked buf[0] for VL flag instead of ret;
- Reorded patches.

 drivers/rtc/rtc-hym8563.c | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

Comments

Alexandre Belloni Dec. 23, 2019, 10:18 a.m. UTC | #1
On 12/12/2019 16:31:11+0100, Paul Kocialkowski wrote:
> The RTC has a valid bit in the seconds register that indicates whether
> power was lost since the pevious time set. This bit is currently read
> once at probe time, cached and updated with set_time.
> 
> Howeever, caching the bit may prevent detecting power loss at runtime
> (which can happen if the RTC's supply is distinct from the the platform's).
> 
> Writing the seconds register when setting time will clear the bit,
> so there should be no downside in reading the bit directly instead of
> caching it.
> 
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
> ---
> Changes since v1:
> - Removed hym8563 unused variables;
> - Checked buf[0] for VL flag instead of ret;
> - Reorded patches.
> 
>  drivers/rtc/rtc-hym8563.c | 19 +++++++------------
>  1 file changed, 7 insertions(+), 12 deletions(-)
Applied, thanks.

Patch
diff mbox series

diff --git a/drivers/rtc/rtc-hym8563.c b/drivers/rtc/rtc-hym8563.c
index fb6d7967ec00..0fb79c4afb46 100644
--- a/drivers/rtc/rtc-hym8563.c
+++ b/drivers/rtc/rtc-hym8563.c
@@ -78,7 +78,6 @@ 
 struct hym8563 {
 	struct i2c_client	*client;
 	struct rtc_device	*rtc;
-	bool			valid;
 #ifdef CONFIG_COMMON_CLK
 	struct clk_hw		clkout_hw;
 #endif
@@ -91,19 +90,19 @@  struct hym8563 {
 static int hym8563_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct i2c_client *client = to_i2c_client(dev);
-	struct hym8563 *hym8563 = i2c_get_clientdata(client);
 	u8 buf[7];
 	int ret;
 
-	if (!hym8563->valid) {
-		dev_warn(&client->dev, "no valid clock/calendar values available\n");
-		return -EINVAL;
-	}
-
 	ret = i2c_smbus_read_i2c_block_data(client, HYM8563_SEC, 7, buf);
 	if (ret < 0)
 		return ret;
 
+	if (buf[0] & HYM8563_SEC_VL) {
+		dev_warn(&client->dev,
+			 "no valid clock/calendar values available\n");
+		return -EINVAL;
+	}
+
 	tm->tm_sec = bcd2bin(buf[0] & HYM8563_SEC_MASK);
 	tm->tm_min = bcd2bin(buf[1] & HYM8563_MIN_MASK);
 	tm->tm_hour = bcd2bin(buf[2] & HYM8563_HOUR_MASK);
@@ -118,7 +117,6 @@  static int hym8563_rtc_read_time(struct device *dev, struct rtc_time *tm)
 static int hym8563_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
 	struct i2c_client *client = to_i2c_client(dev);
-	struct hym8563 *hym8563 = i2c_get_clientdata(client);
 	u8 buf[7];
 	int ret;
 
@@ -157,8 +155,6 @@  static int hym8563_rtc_set_time(struct device *dev, struct rtc_time *tm)
 	if (ret < 0)
 		return ret;
 
-	hym8563->valid = true;
-
 	return 0;
 }
 
@@ -556,9 +552,8 @@  static int hym8563_probe(struct i2c_client *client,
 	if (ret < 0)
 		return ret;
 
-	hym8563->valid = !(ret & HYM8563_SEC_VL);
 	dev_dbg(&client->dev, "rtc information is %s\n",
-		hym8563->valid ? "valid" : "invalid");
+		(ret & HYM8563_SEC_VL) ? "invalid" : "valid");
 
 	hym8563->rtc = devm_rtc_device_register(&client->dev, client->name,
 						&hym8563_rtc_ops, THIS_MODULE);