[PATCH] rtc: rtc-at91rm9200: fix lost ACKUPD interrupt

Boris BREZILLON boris.brezillon at free-electrons.com
Mon May 5 13:23:08 PDT 2014

If an alarm interrupt raises just after the CR register is written and
before the ACKUPD is unmasked the ACKUPD bit might be cleaned up without
waking up the waiting thread.

Unmask the ACKUPD interrupt before writing the CR register so that the
ACKUPD cannot be lost.

Signed-off-by: Boris BREZILLON <boris.brezillon at free-electrons.com>
Reported-by: Bryan Evenson <bevenson at melinkcorp.com>
Hello Bryan,

Could you try to apply this patch and tell me if it fixes your bug ?

Best Regards,


 drivers/rtc/rtc-at91rm9200.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-at91rm9200.c b/drivers/rtc/rtc-at91rm9200.c
index 3281c90..c16c423 100644
--- a/drivers/rtc/rtc-at91rm9200.c
+++ b/drivers/rtc/rtc-at91rm9200.c
@@ -163,9 +163,9 @@ static int at91_rtc_settime(struct device *dev, struct rtc_time *tm)
 	/* Stop Time/Calendar from counting */
 	cr = at91_rtc_read(AT91_RTC_CR);
+	at91_rtc_write_ier(AT91_RTC_ACKUPD);
 	at91_rtc_write(AT91_RTC_CR, cr | AT91_RTC_UPDCAL | AT91_RTC_UPDTIM);
-	at91_rtc_write_ier(AT91_RTC_ACKUPD);
 	wait_for_completion(&at91_rtc_updated);	/* wait for ACKUPD interrupt */

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