Date: 9 Jan 2006 21:32:25 +0100
Date: Mon, 9 Jan 2006 21:32:25 +0100
From: Andi Kleen <ak@muc.de>
To: lkml@cl.domainfactory-kunde.de
Cc: Clemens Ladisch <clemens@ladisch.de>, Andrew Morton <akpm@osdl.org>,
       Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>,
       Vojtech Pavlik <vojtech@suse.cz>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] HPET RTC emulation: add watchdog timer
Message-ID: <20060109203225.GA93253@muc.de>
References: <20060109154350.GA22126@turing.informatik.uni-halle.de> <20060109164140.GA67021@muc.de> <1136829634.43c2a4c2e0997@www.domainfactory-webmail.de>
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On Mon, Jan 09, 2006 at 07:00:34PM +0100, lkml@cl.domainfactory-kunde.de wrote:
> Andi Kleen wrote:
> > On Mon, Jan 09, 2006 at 04:43:50PM +0100, Clemens Ladisch wrote:
> > > To prevent the emulated RTC timer from stopping when interrupts
> > > are disabled for too long, implement the watchdog timer to
> > > restart it when needed.
> >
> > The interrupt handler should just read the time (it likely
> > has to do that anyways)
> 
> Not in the current implementation.

The standard HPET interrupt in x86-64 does this already at least.

> > and check for that directly.
> 
> I want to avoid the read altogether because the round trip to the
> south bridge is rather slow (1.5 microseconds with VIA chipsets).

You can use the TSC to detect it too, but it might be unreliable.

-Andi

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