linux-kernel - RE: [PATCH] rtc: rtc-at91rm9200: fix lost ACKUPD interrupt

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Date:	Mon, 5 May 2014 20:44:48 +0000
From:	Bryan Evenson <bevenson@...inkcorp.com>
To:	Boris BREZILLON <boris.brezillon@...e-electrons.com>
CC:	Andrew Victor <linux@...im.org.za>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	"rtc-linux@...glegroups.com" <rtc-linux@...glegroups.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] rtc: rtc-at91rm9200: fix lost ACKUPD interrupt

Boris,

> -----Original Message-----
> From: Boris BREZILLON [mailto:boris.brezillon@...e-electrons.com]
> Sent: Monday, May 05, 2014 4:23 PM
> To: Bryan Evenson
> Cc: Andrew Victor; Nicolas Ferre; Jean-Christophe Plagniol-Villard; linux-arm-
> kernel@...ts.infradead.org; Alessandro Zummo; rtc-
> linux@...glegroups.com; linux-kernel@...r.kernel.org; Boris BREZILLON
> Subject: [PATCH] rtc: rtc-at91rm9200: fix lost ACKUPD interrupt
> 
> 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@...e-electrons.com>
> Reported-by: Bryan Evenson <bevenson@...inkcorp.com>
> ---
> Hello Bryan,
> 
> Could you try to apply this patch and tell me if it fixes your bug ?
> 

I'll incorporate the patch and see what happens.  I'll be able to let you know the results tomorrow morning.

Regards,
Bryan

> Best Regards,
> 
> Boris
> 
>  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 */
>  	at91_rtc_write_idr(AT91_RTC_ACKUPD);
> 
> --
> 1.8.3.2

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