linux-kernel - Re: + rtc-disable-hpet-emulation-on-suspend.patch added to -mm tree

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Date:	Wed, 14 Oct 2009 07:56:39 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	akpm@...ux-foundation.org
Cc:	mm-commits@...r.kernel.org, maximlevitsky@...il.com,
	david-b@...bell.net, hpa@...or.com, rjw@...k.pl,
	tglx@...utronix.de, linux-kernel@...r.kernel.org,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: + rtc-disable-hpet-emulation-on-suspend.patch added to -mm tree


* akpm@...ux-foundation.org <akpm@...ux-foundation.org> wrote:

> ------------------------------------------------------
> Subject: rtc: disable hpet emulation on suspend
> From: Maxim Levitsky <maximlevitsky@...il.com>
> 
> I noticed that rtc wont generate interrupts after a resume from disk.
> Here hpet rtc emulation is used.
> 
> Problem is that rtc hpet comparator, isn't reinitialized after resume.
> Easiest way to solve this, is always mask all hpet interrupts on suspend
> This is triggered, when suspending with alarm set.
> 
> 
> Otherwise, hpet driver will think it doesn't need to reinitialize
> the rtc comparator, thus rtc interrupts won't work.
> 
> This emulation isn't need for wakealarm.

> -		hpet_mask_rtc_irq_bit(mask);
>  
> +		/* shut down hpet emulation - we don't need it for alarm */
> +		hpet_mask_rtc_irq_bit(RTC_PIE|RTC_AIE|RTC_UIE);
>  		cmos_checkintr(cmos, tmp);

Would be nice to also unconditionally reinitialize the hpet/rtc after 
resume - regardless of what state we left it in.

Also, are you sure this does not break things like 
CONFIG_PM_TEST_SUSPEND=y which rely on wakealarm?

	Ingo
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