linux-kernel - Re: [PATCH] Don't disable hpet emulation on suspend

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Date:	Wed, 10 Apr 2013 16:58:01 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Derek Basehore <dbasehore@...omium.org>
Cc:	rtc-linux@...glegroups.com,
	Alessandro Zummo <a.zummo@...ertech.it>,
	linux-kernel@...r.kernel.org,
	Maxim Levitsky <maximlevitsky@...il.com>
Subject: Re: [PATCH] Don't disable hpet emulation on suspend

On Tue,  9 Apr 2013 17:36:13 -0700 Derek Basehore <dbasehore@...omium.org> wrote:

> There's a bug where rtc alarms are ignored after the rtc cmos suspends but
> before the system finishes suspend. Since hpet emulation is disabled and it
> still handles the interrupts, a wake event is never registered which is done
> from the rtc layer. This reverts an earlier commit which disables hpet
> emulation. To fix the problem mentioned in that commit, the hpet_rtc_timer_init
> function is called directly on resume.
> 
> This reverts commit d1b2efa83fbf7b33919238fa29ef6ab935820103.
> 
> ...
>
> --- a/drivers/rtc/rtc-cmos.c
> +++ b/drivers/rtc/rtc-cmos.c
> @@ -804,9 +804,8 @@ static int cmos_suspend(struct device *dev)
>  			mask = RTC_IRQMASK;
>  		tmp &= ~mask;
>  		CMOS_WRITE(tmp, RTC_CONTROL);
> +		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);
>  	}
>  	spin_unlock_irq(&rtc_lock);
> @@ -870,6 +869,7 @@ static int cmos_resume(struct device *dev)
>  			rtc_update_irq(cmos->rtc, 1, mask);
>  			tmp &= ~RTC_AIE;
>  			hpet_mask_rtc_irq_bit(RTC_AIE);
> +			hpet_rtc_timer_init();
>  		} while (mask & RTC_AIE);
>  		spin_unlock_irq(&rtc_lock);
>  	}

huh, so it's been broken for three years.

This calls hpet_rtc_timer_init() under spin_lock_irq() which is OK with
the current implementation.  And things should be OK when
CONFIG_HPET_EMULATE_RTC=n.

Maxim, can you please review/test/etc?
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