2021-10-17 21:16:37

by Alexandre Belloni

[permalink] [raw]
Subject: [PATCH] rtc: pcf8523: avoid reading BLF in pcf8523_rtc_read_time

BLF, battery low doesn't mean the time is imprecise or invalid, it simply mean
the backup battery has to be replaced. This information can be read using the
VL_READ ioctl.

Signed-off-by: Alexandre Belloni <[email protected]>
---
drivers/rtc/rtc-pcf8523.c | 26 ++++----------------------
1 file changed, 4 insertions(+), 22 deletions(-)

diff --git a/drivers/rtc/rtc-pcf8523.c b/drivers/rtc/rtc-pcf8523.c
index 8b6fb20774bf..09110b3ae25f 100644
--- a/drivers/rtc/rtc-pcf8523.c
+++ b/drivers/rtc/rtc-pcf8523.c
@@ -24,6 +24,7 @@
#define PCF8523_CONTROL3_PM_DSM BIT(5) /* direct switching mode */
#define PCF8523_CONTROL3_PM_MASK 0xe0
#define PCF8523_CONTROL3_BLF BIT(2) /* battery low bit, read-only */
+#define PCF8523_CONTROL3_BSF BIT(3)

#define PCF8523_REG_SECONDS 0x03
#define PCF8523_SECONDS_OS BIT(7)
@@ -94,18 +95,6 @@ static int pcf8523_write(struct i2c_client *client, u8 reg, u8 value)
return 0;
}

-static int pcf8523_voltage_low(struct i2c_client *client)
-{
- u8 value;
- int err;
-
- err = pcf8523_read(client, PCF8523_REG_CONTROL3, &value);
- if (err < 0)
- return err;
-
- return !!(value & PCF8523_CONTROL3_BLF);
-}
-
static int pcf8523_load_capacitance(struct i2c_client *client)
{
u32 load;
@@ -220,14 +209,6 @@ static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm)
struct i2c_msg msgs[2];
int err;

- err = pcf8523_voltage_low(client);
- if (err < 0) {
- return err;
- } else if (err > 0) {
- dev_err(dev, "low voltage detected, time is unreliable\n");
- return -EINVAL;
- }
-
msgs[0].addr = client->addr;
msgs[0].flags = 0;
msgs[0].len = 1;
@@ -412,10 +393,11 @@ static int pcf8523_rtc_ioctl(struct device *dev, unsigned int cmd,

switch (cmd) {
case RTC_VL_READ:
- ret = pcf8523_voltage_low(client);
+ ret = pcf8523_read(client, PCF8523_REG_CONTROL3, &value);
if (ret < 0)
return ret;
- if (ret)
+
+ if (value & PCF8523_CONTROL3_BLF)
flags |= RTC_VL_BACKUP_LOW;

ret = pcf8523_read(client, PCF8523_REG_SECONDS, &value);
--
2.31.1