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    Subject[PATCH 3.13 106/198] rtc: rtc-at91rm9200: fix infinite wait for ACKUPD irq
    Date
    3.13.11.5 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Boris BREZILLON <boris.brezillon@free-electrons.com>

    commit 2fe121e1f5aa3bf31b418a9790db6c400e922291 upstream.

    The rtc user must wait at least 1 sec between each time/calandar update
    (see atmel's datasheet chapter "Updating Time/Calendar").

    Use the 1Hz interrupt to update the at91_rtc_upd_rdy flag and wait for
    the at91_rtc_wait_upd_rdy event if the rtc is not ready.

    This patch fixes a deadlock in an uninterruptible wait when the RTC is
    updated more than once every second. AFAICT the bug is here from the
    beginning, but I think we should at least backport this fix to 3.10 and
    the following longterm and stable releases.

    Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
    Reported-by: Bryan Evenson <bevenson@melinkcorp.com>
    Tested-by: Bryan Evenson <bevenson@melinkcorp.com>
    Cc: Andrew Victor <linux@maxim.org.za>
    Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
    Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
    Cc: Alessandro Zummo <a.zummo@towertech.it>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    drivers/rtc/rtc-at91rm9200.c | 16 ++++++++++++++--
    1 file changed, 14 insertions(+), 2 deletions(-)

    diff --git a/drivers/rtc/rtc-at91rm9200.c b/drivers/rtc/rtc-at91rm9200.c
    index 3281c90..44fe83e 100644
    --- a/drivers/rtc/rtc-at91rm9200.c
    +++ b/drivers/rtc/rtc-at91rm9200.c
    @@ -48,6 +48,7 @@ struct at91_rtc_config {

    static const struct at91_rtc_config *at91_rtc_config;
    static DECLARE_COMPLETION(at91_rtc_updated);
    +static DECLARE_COMPLETION(at91_rtc_upd_rdy);
    static unsigned int at91_alarm_year = AT91_RTC_EPOCH;
    static void __iomem *at91_rtc_regs;
    static int irq;
    @@ -161,6 +162,8 @@ static int at91_rtc_settime(struct device *dev, struct rtc_time *tm)
    1900 + tm->tm_year, tm->tm_mon, tm->tm_mday,
    tm->tm_hour, tm->tm_min, tm->tm_sec);

    + wait_for_completion(&at91_rtc_upd_rdy);
    +
    /* Stop Time/Calendar from counting */
    cr = at91_rtc_read(AT91_RTC_CR);
    at91_rtc_write(AT91_RTC_CR, cr | AT91_RTC_UPDCAL | AT91_RTC_UPDTIM);
    @@ -183,7 +186,9 @@ static int at91_rtc_settime(struct device *dev, struct rtc_time *tm)

    /* Restart Time/Calendar */
    cr = at91_rtc_read(AT91_RTC_CR);
    + at91_rtc_write(AT91_RTC_SCCR, AT91_RTC_SECEV);
    at91_rtc_write(AT91_RTC_CR, cr & ~(AT91_RTC_UPDCAL | AT91_RTC_UPDTIM));
    + at91_rtc_write_ier(AT91_RTC_SECEV);

    return 0;
    }
    @@ -290,8 +295,10 @@ static irqreturn_t at91_rtc_interrupt(int irq, void *dev_id)
    if (rtsr) { /* this interrupt is shared! Is it ours? */
    if (rtsr & AT91_RTC_ALARM)
    events |= (RTC_AF | RTC_IRQF);
    - if (rtsr & AT91_RTC_SECEV)
    - events |= (RTC_UF | RTC_IRQF);
    + if (rtsr & AT91_RTC_SECEV) {
    + complete(&at91_rtc_upd_rdy);
    + at91_rtc_write_idr(AT91_RTC_SECEV);
    + }
    if (rtsr & AT91_RTC_ACKUPD)
    complete(&at91_rtc_updated);

    @@ -413,6 +420,11 @@ static int __init at91_rtc_probe(struct platform_device *pdev)
    return PTR_ERR(rtc);
    platform_set_drvdata(pdev, rtc);

    + /* enable SECEV interrupt in order to initialize at91_rtc_upd_rdy
    + * completion.
    + */
    + at91_rtc_write_ier(AT91_RTC_SECEV);
    +
    dev_info(&pdev->dev, "AT91 Real Time Clock driver.\n");
    return 0;
    }
    --
    1.9.1


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