target/linux/brcm2708/patches-4.4/0353-rtc-ds1307-ensure-that-any-pending-alarm-is-cleared-.patch

   1 From dab463aa0dbd5ac45403dade2723046eba214359 Mon Sep 17 00:00:00 2001
   2 From: Nicolas Boullis <nboullis@debian.org>
   3 Date: Sun, 10 Apr 2016 13:23:05 +0200
   4 Subject: [PATCH] rtc: ds1307: ensure that any pending alarm is cleared before
   5  a new alarm is enabled
   6 MIME-Version: 1.0
   7 Content-Type: text/plain; charset=UTF-8
   8 Content-Transfer-Encoding: 8bit
   9
  10 If a previously-set alarm was disabled and then triggered, it may still
  11 be pending when a new alarm is configured.
  12
  13 Then, if the alarm is enabled before the pending alarm is cleared, then
  14 an interrupt is immediately raised.
  15
  16 Unfortunately, when the alarm is cleared and enabled during the same I²C
  17 block write, the chip (at least the DS1339 I have) considers that the
  18 alarm is enabled before it is cleared, and raises an interrupt.
  19
  20 This patch ensures that the pending alarm is cleared before the alarm is
  21 enabled.
  22
  23 Signed-off-by: Nicolas Boullis <nboullis@debian.org>
  24 Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
  25 ---
  26  drivers/rtc/rtc-ds1307.c | 13 ++++++++-----
  27  1 file changed, 8 insertions(+), 5 deletions(-)
  28
  29 --- a/drivers/rtc/rtc-ds1307.c
  30 +++ b/drivers/rtc/rtc-ds1307.c
  31 @@ -540,12 +540,8 @@ static int ds1337_set_alarm(struct devic
  32         buf[5] = 0;
  33         buf[6] = 0;
  34
  35 -       /* optionally enable ALARM1 */
  36 +       /* disable alarms */
  37         buf[7] = control & ~(DS1337_BIT_A1IE | DS1337_BIT_A2IE);
  38 -       if (t->enabled) {
  39 -               dev_dbg(dev, "alarm IRQ armed\n");
  40 -               buf[7] |= DS1337_BIT_A1IE;      /* only ALARM1 is used */
  41 -       }
  42         buf[8] = status & ~(DS1337_BIT_A1I | DS1337_BIT_A2I);
  43
  44         ret = ds1307->write_block_data(client,
  45 @@ -555,6 +551,13 @@ static int ds1337_set_alarm(struct devic
  46                 return ret;
  47         }
  48
  49 +       /* optionally enable ALARM1 */
  50 +       if (t->enabled) {
  51 +               dev_dbg(dev, "alarm IRQ armed\n");
  52 +               buf[7] |= DS1337_BIT_A1IE;      /* only ALARM1 is used */
  53 +               i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL, buf[7]);
  54 +       }
  55 +
  56         return 0;
  57  }
  58