linux-kernel - Re: [REGRESSION] rtc/interface.c: kills suspend-to-ram

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Message-ID: <4F8C926D.2040503@linaro.org>
Date:	Mon, 16 Apr 2012 14:43:09 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Mark Lord <kernel@...savvy.com>
CC:	richard -rw- weinberger <richard.weinberger@...il.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	rtc-linux@...glegroups.com,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Greg Kroah-Hartman <greg@...ah.com>, stable@...r.kernel.org,
	Rabin Vincent <rabin.vincent@...ricsson.com>
Subject: Re: [REGRESSION] rtc/interface.c: kills suspend-to-ram

On 04/16/2012 12:45 PM, John Stultz wrote:
> On 04/16/2012 08:57 AM, Mark Lord wrote:
>> On 12-04-16 11:49 AM, richard -rw- weinberger wrote:
>>> On Mon, Apr 16, 2012 at 5:42 PM, Mark Lord<kernel@...savvy.com>  wrote:
>>>> On 12-04-16 10:23 AM, richard -rw- weinberger wrote:
>>>>> On Mon, Apr 16, 2012 at 3:55 PM, Mark Lord<kernel@...savvy.com>  
>>>>> wrote:
>>>>>> On 12-04-16 12:36 AM, Mark Lord wrote:
>>>>>>> Something recent has killed suspend-to-ram on a number of 
>>>>>>> machines here.
>>>>>>> The symptom is that they suspend, but immediately wake up and 
>>>>>>> panic,
>>>>>>> with just a black screen so no visible messages to go by.
>>>>>>>
>>>>>>> The patch below works around the issue -- making things work as 
>>>>>>> they used to work.
>>>>>>>
>>>>>>> +++ linux/drivers/rtc/interface.c     2012-04-16 
>>>>>>> 00:09:14.105387382 -0400
>>>>>>> @@ -773,7 +773,7 @@
>>>>>>>        if (!rtc->ops || !rtc->ops->alarm_irq_enable)
>>>>>>>                return;
>>>>>>>
>>>>>>> -     rtc->ops->alarm_irq_enable(rtc->dev.parent, false);
>>>>>>> +     //rtc->ops->alarm_irq_enable(rtc->dev.parent, false);  // 
>>>>>>> Kills suspend on ZBOX HD-ID41U
>>>>>>>   }
>>>>
>>>> How about the line above -- that's the commit that breaks things here.
>>> Download Linus' GIT tree and use git blame. :-)
>> Too steep a learning curve for a casual user.
>> But google works:
>>
>> http://www.mail-archive.com/stable@vger.kernel.org/msg04391.html
>
> Thanks for the report and sorry for the trouble.  I'm trying to 
> reproduce this locally. Can you send me your .config?

Ok, so far I've not been able to reproduce anything like this with my 
atom x86_64 system (done a number of suspends both with and without RTC 
alarms queued to wake the system up).  Can you provide any more details 
about how you're triggering suspend when you see the problem?
Do you have an RTC alarm set for some future time to wake up the system?
I'm just trying to understand when rtc_alarm_disable is being called and 
causing the trouble in your case.

The original related issue with the earlier version of this patch was 
some hardware would wake up immediately after suspend if the rtc was set 
in the past (which is what was done to "disable" the alarm).  I suspect 
there is a similar hardware quirk we're dealing with that may require 
extra logic in the rtc-cmos.c alarm_irq_enable() function.

thanks
-john


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