queue-4.9/rtc-pcf8523-don-t-return-invalid-date-when-battery-is-low.patch

   1 From ecb4a353d3afd45b9bb30c85d03ee113a0589079 Mon Sep 17 00:00:00 2001
   2 From: Baruch Siach <baruch@tkos.co.il>
   3 Date: Wed, 5 Dec 2018 17:00:09 +0200
   4 Subject: rtc: pcf8523: don't return invalid date when battery is low
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 From: Baruch Siach <baruch@tkos.co.il>
  10
  11 commit ecb4a353d3afd45b9bb30c85d03ee113a0589079 upstream.
  12
  13 The RTC_VL_READ ioctl reports the low battery condition. Still,
  14 pcf8523_rtc_read_time() happily returns invalid dates in this case.
  15 Check the battery health on pcf8523_rtc_read_time() to avoid that.
  16
  17 Reported-by: Erik Čuk <erik.cuk@domel.com>
  18 Signed-off-by: Baruch Siach <baruch@tkos.co.il>
  19 Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
  20 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  21
  22 ---
  23  drivers/rtc/rtc-pcf8523.c |   32 ++++++++++++++++++++++++--------
  24  1 file changed, 24 insertions(+), 8 deletions(-)
  25
  26 --- a/drivers/rtc/rtc-pcf8523.c
  27 +++ b/drivers/rtc/rtc-pcf8523.c
  28 @@ -82,6 +82,18 @@ static int pcf8523_write(struct i2c_clie
  29         return 0;
  30  }
  31
  32 +static int pcf8523_voltage_low(struct i2c_client *client)
  33 +{
  34 +       u8 value;
  35 +       int err;
  36 +
  37 +       err = pcf8523_read(client, REG_CONTROL3, &value);
  38 +       if (err < 0)
  39 +               return err;
  40 +
  41 +       return !!(value & REG_CONTROL3_BLF);
  42 +}
  43 +
  44  static int pcf8523_select_capacitance(struct i2c_client *client, bool high)
  45  {
  46         u8 value;
  47 @@ -164,6 +176,14 @@ static int pcf8523_rtc_read_time(struct
  48         struct i2c_msg msgs[2];
  49         int err;
  50
  51 +       err = pcf8523_voltage_low(client);
  52 +       if (err < 0) {
  53 +               return err;
  54 +       } else if (err > 0) {
  55 +               dev_err(dev, "low voltage detected, time is unreliable\n");
  56 +               return -EINVAL;
  57 +       }
  58 +
  59         msgs[0].addr = client->addr;
  60         msgs[0].flags = 0;
  61         msgs[0].len = 1;
  62 @@ -248,17 +268,13 @@ static int pcf8523_rtc_ioctl(struct devi
  63                              unsigned long arg)
  64  {
  65         struct i2c_client *client = to_i2c_client(dev);
  66 -       u8 value;
  67 -       int ret = 0, err;
  68 +       int ret;
  69
  70         switch (cmd) {
  71         case RTC_VL_READ:
  72 -               err = pcf8523_read(client, REG_CONTROL3, &value);
  73 -               if (err < 0)
  74 -                       return err;
  75 -
  76 -               if (value & REG_CONTROL3_BLF)
  77 -                       ret = 1;
  78 +               ret = pcf8523_voltage_low(client);
  79 +               if (ret < 0)
  80 +                       return ret;
  81
  82                 if (copy_to_user((void __user *)arg, &ret, sizeof(int)))
  83                         return -EFAULT;