• Johan Hovold's avatar
    ARM: at91: fix hanged boot due to early rtc-interrupt · 6de714c2
    Johan Hovold authored
    Make sure the RTC-interrupts are masked at boot by adding a new helper
    function to be used at SOC-init.
    
    This fixes hanged boot on all AT91 SOCs with an RTC (but RM9200), for
    example, after a reset during an RTC-update or if an RTC-alarm goes off
    after shutdown (e.g. when using RTC wakeup).
    
    The RTC and RTT-peripherals are powered by backup power (VDDBU) (on all
    AT91 SOCs but RM9200) and are not reset on wake-up, user, watchdog or
    software reset. This means that their interrupts may be enabled during
    early boot if, for example, they where not disabled during a previous
    shutdown (e.g. due to a buggy driver or a non-clean shutdown such as a
    user reset). Furthermore, an RTC or RTT-alarm may also be active.
    
    The RTC and RTT-interrupts use the shared system-interrupt line, which
    is also used by the PIT, and if an interrupt occurs before a handler
    (e.g. RTC-driver) has been installed this leads to the system interrupt
    being disabled and prevents the system from booting.
    
    Note that when boot hangs due to an early RTC or RTT-interrupt, the only
    way to get the system to start again is to remove the backup power (e.g.
    battery) or to disable the interrupt manually from the bootloader. In
    particular, a user reset is not sufficient.
    Signed-off-by: default avatarJohan Hovold <jhovold@gmail.com>
    Signed-off-by: default avatarNicolas Ferre <nicolas.ferre@atmel.com>
    Cc: stable@vger.kernel.org # 3.11.x
    6de714c2
at91sam9n12.h 2.28 KB