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Subject[PATCH 4.14 53/53] rtc: pcf8523: dont return invalid date when battery is low
Date
From: Baruch Siach <baruch@tkos.co.il>

commit ecb4a353d3afd45b9bb30c85d03ee113a0589079 upstream.

The RTC_VL_READ ioctl reports the low battery condition. Still,
pcf8523_rtc_read_time() happily returns invalid dates in this case.
Check the battery health on pcf8523_rtc_read_time() to avoid that.

Reported-by: Erik Čuk <erik.cuk@domel.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/rtc/rtc-pcf8523.c | 32 ++++++++++++++++++++++++--------
1 file changed, 24 insertions(+), 8 deletions(-)

--- a/drivers/rtc/rtc-pcf8523.c
+++ b/drivers/rtc/rtc-pcf8523.c
@@ -82,6 +82,18 @@ static int pcf8523_write(struct i2c_clie
return 0;
}

+static int pcf8523_voltage_low(struct i2c_client *client)
+{
+ u8 value;
+ int err;
+
+ err = pcf8523_read(client, REG_CONTROL3, &value);
+ if (err < 0)
+ return err;
+
+ return !!(value & REG_CONTROL3_BLF);
+}
+
static int pcf8523_select_capacitance(struct i2c_client *client, bool high)
{
u8 value;
@@ -164,6 +176,14 @@ static int pcf8523_rtc_read_time(struct
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;
@@ -248,17 +268,13 @@ static int pcf8523_rtc_ioctl(struct devi
unsigned long arg)
{
struct i2c_client *client = to_i2c_client(dev);
- u8 value;
- int ret = 0, err;
+ int ret;

switch (cmd) {
case RTC_VL_READ:
- err = pcf8523_read(client, REG_CONTROL3, &value);
- if (err < 0)
- return err;
-
- if (value & REG_CONTROL3_BLF)
- ret = 1;
+ ret = pcf8523_voltage_low(client);
+ if (ret < 0)
+ return ret;

if (copy_to_user((void __user *)arg, &ret, sizeof(int)))
return -EFAULT;

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