Commit 2fe121e1 authored by Boris BREZILLON's avatar Boris BREZILLON Committed by Linus Torvalds
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rtc: rtc-at91rm9200: fix infinite wait for ACKUPD irq 



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: default avatarBoris BREZILLON <boris.brezillon@free-electrons.com>
Reported-by: default avatarBryan Evenson <bevenson@melinkcorp.com>
Tested-by: default avatarBryan 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>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 68164a73

drivers/rtc/rtc-at91rm9200.c

+14 −2
Original line number Diff line number Diff line
@@ -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;

}

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