Merge tag 'timers-urgent-2021-01-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer fix from Thomas Gleixner:
 "A fix for handling advertised, but non-existent 146818 RTCs correctly.

  With the recent UIP handling changes the time readout of non-existent
  RTCs hangs forever as the read returns always 0xFF which means the UIP
  bit is set.

  Sanity check the RTC before registering by checking the RTC_VALID
  register for correctness"

* tag 'timers-urgent-2021-01-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  rtc: mc146818: Detect and handle broken RTCs