linux-kernel - HPET rtc emulation

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Date:	Tue, 30 Apr 2013 09:26:42 +0200
From:	Christian Gmeiner <christian.gmeiner@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>, venki@...gle.com,
	Thomas Gleixner <tglx@...utronix.de>
Subject: HPET rtc emulation

Hi.

I am working with a platform that has a problem with the RTC alarm
interrupt - tested with rtctest from /Documentation/rtc.txt.
So I thought that I could use the HPET emulation. As far as I
understand in the HPET emulation mode no RTC irq will be used --> RTC
alarm interrupt is done via HPET.
Is this a correct assumption?

root@OT:/home/vis# hwclock
Tue 30 Apr 2013 09:24:28 AM CEST  -0.511012 seconds
root@OT:/home/vis# hwclock
Tue 30 Apr 2013 09:24:29 AM CEST  -0.511016 seconds
root@OT:/home/vis# hwclock
Tue 30 Apr 2013 09:24:30 AM CEST  -0.526659 seconds
root@OT:/home/vis# hwclock
Tue 30 Apr 2013 09:24:31 AM CEST  -0.620384 seconds
root@OT:/home/vis# hwclock
Tue 30 Apr 2013 09:24:32 AM CEST  -0.604838 seconds
root@OT:/home/vis# hwclock
Tue 30 Apr 2013 09:24:33 AM CEST  -0.651638 seconds
root@OT:/home/vis# hwclock
Tue 30 Apr 2013 09:24:34 AM CEST  -0.682915 seconds
root@OT:/home/vis# hwclock
Tue 30 Apr 2013 09:24:35 AM CEST  -0.026708 seconds
root@OT:/home/vis# hwclock
select() to /dev/rtc to wait for clock tick timed ou


Doing some quite simple tests indicates that HPET emulation does not emulate
RTC alarm interrupts or my HPET has some problems.

thanks
--
Christian Gmeiner, MSc
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