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    Subject[PATCH v2 1/5] ARM: at91/rtc: fix boot after RTC wake-up
    Date
    Fix failed boot after RTC wake-up by making sure RTC-interrupts are
    disabled at shutdown.

    The RTC-registers are not reset at shutdown when there is backup power
    available, and hence the RTC-interrupt, which uses the shared system
    interrupt, may be enabled during early boot. If an RTC-alarm goes off
    before the RTC-driver is initialised (e.g. when waking up from an
    RTC-alarm) this results in disabled system interrupts.

    Without earlyprintk boot hangs after

    Uncompressing Linux... done, booting the kernel.

    and earlyprintk reveals that the shared system interrupt gets disabled:

    irq 17: nobody cared (try booting with the "irqpoll" option)
    [<c000cf8c>] (unwind_backtrace+0x0/0xf0) from [<c00513ec>] (__report_bad_irq+0x20/0xe8)
    [<c00513ec>] (__report_bad_irq+0x20/0xe8) from [<c00516fc>] (note_interrupt+0x1e0/0x244)
    [<c00516fc>] (note_interrupt+0x1e0/0x244) from [<c004f980>] (handle_irq_event_percpu+0xac/0x1c4)
    [<c004f980>] (handle_irq_event_percpu+0xac/0x1c4) from [<c004faec>] (handle_irq_event+0x54/0x84)
    [<c004faec>] (handle_irq_event+0x54/0x84) from [<c0052364>] (handle_fasteoi_irq+0x84/0x154)
    [<c0052364>] (handle_fasteoi_irq+0x84/0x154) from [<c004f1f8>] (generic_handle_irq+0x20/0x30)
    [<c004f1f8>] (generic_handle_irq+0x20/0x30) from [<c0009b8c>] (handle_IRQ+0x30/0x84)
    [<c0009b8c>] (handle_IRQ+0x30/0x84) from [<c0008fa0>] (__irq_svc+0x40/0x6c)
    [<c0008fa0>] (__irq_svc+0x40/0x6c) from [<c001cd6c>] (__do_softirq+0x5c/0x164)
    [<c001cd6c>] (__do_softirq+0x5c/0x164) from [<c001d268>] (irq_exit+0x58/0x60)
    [<c001d268>] (irq_exit+0x58/0x60) from [<c0009b90>] (handle_IRQ+0x34/0x84)
    [<c0009b90>] (handle_IRQ+0x34/0x84) from [<c0008fa0>] (__irq_svc+0x40/0x6c)
    [<c0008fa0>] (__irq_svc+0x40/0x6c) from [<c03e668c>] (start_kernel+0x1d8/0x29c)
    [<c03e668c>] (start_kernel+0x1d8/0x29c) from [<70008040>] (0x70008040)
    handlers:
    [<c0012df0>] at91sam926x_pit_interrupt
    Disabling IRQ #17

    Note that disabling the RTC-interrupts at shutdown fixes boot after a
    clean shutdown, but that an RTC-alarm after a user (or watchdog) reset
    could still prevent the system from booting.

    Note also that the only way to recover from a failed boot after an
    RTC-alarm is to remove any backup power (e.g. backup battery) or to
    disable (or acknowledge) the RTC-interrupt manually from the bootloader.
    In particular, a user-reset is not sufficient.

    Tested on at91sam9g45.

    Cc: stable <stable@vger.kernel.org>
    Signed-off-by: Johan Hovold <jhovold@gmail.com>
    ---
    drivers/rtc/rtc-at91rm9200.c | 9 +++++++++
    1 file changed, 9 insertions(+)

    diff --git a/drivers/rtc/rtc-at91rm9200.c b/drivers/rtc/rtc-at91rm9200.c
    index b6469e2..936c75a 100644
    --- a/drivers/rtc/rtc-at91rm9200.c
    +++ b/drivers/rtc/rtc-at91rm9200.c
    @@ -338,6 +338,14 @@ static int __exit at91_rtc_remove(struct platform_device *pdev)
    return 0;
    }

    +static void at91_rtc_shutdown(struct platform_device *pdev)
    +{
    + /* Disable all interrupts */
    + at91_rtc_write(AT91_RTC_IDR, AT91_RTC_ACKUPD | AT91_RTC_ALARM |
    + AT91_RTC_SECEV | AT91_RTC_TIMEV |
    + AT91_RTC_CALEV);
    +}
    +
    #ifdef CONFIG_PM

    /* AT91RM9200 RTC Power management control */
    @@ -384,6 +392,7 @@ static const struct dev_pm_ops at91_rtc_pm = {

    static struct platform_driver at91_rtc_driver = {
    .remove = __exit_p(at91_rtc_remove),
    + .shutdown = at91_rtc_shutdown,
    .driver = {
    .name = "at91_rtc",
    .owner = THIS_MODULE,
    --
    1.8.1.5


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