Subject: Re: [RFC][PATCH] x86_64:  Fix collision between pmtimer and
	pit/hpet timekeeping
From: john stultz <johnstul@us.ibm.com>
To: Andi Kleen <ak@suse.de>
Cc: lkml <linux-kernel@vger.kernel.org>, Chris McDermott <lcm@us.ibm.com>,
       vojtech@suse.cz
In-Reply-To: <20051207175338.GB11190@wotan.suse.de>
References: <1133931639.10613.39.camel@cog.beaverton.ibm.com>
	 <20051207175338.GB11190@wotan.suse.de>
Content-Type: text/plain
Date: Wed, 07 Dec 2005 10:00:30 -0800
Message-Id: <1133978430.18188.3.camel@leatherman>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1736
Lines: 44

On Wed, 2005-12-07 at 18:53 +0100, Andi Kleen wrote:
> On Tue, Dec 06, 2005 at 09:00:39PM -0800, john stultz wrote:
> > Hello,
> > 	I thought I had caught all the problems when the no-legacy HPET support
> > landed close to the time that the ACPI PM timer support landed, but
> > apparently not. :(
> > 
> > On systems that do not support the HPET legacy functions (basically the
> > IBM x460, but there could be others), in time_init() we accidentally
> > fall into a PM timer conditional and set the vxtime_hz value to the PM
> > timer's frequency. We then use this value with the HPET for timekeeping.
> > 
> > This patch (which mimics the behavior in time_init_gtod) corrects the
> > collision.
> > 
> > Andi, any objections or suggestions for a better way?
> 
> Ok. I will apply it.
> 
> But I never quite got why you fall back to the PIT on these systems
> anyways - if LEGSUP is not set it just means that the HPET interrupt
> cannot be routed to irq 0, right? It should be quite easy to change
> the timer code to accept timer interrupts on other irqs. 
> 
> You just need to allocate the other interrupt and possibly coordinate
> that with the hpet char driver (or rather move the code for that
> from there to time.c). I think implementing that would be a better
> solution.

Indeed that does sound like a decent cleanup. I can't promise anything
in the near future, but its on my list.

Would you then want to move all systems to use the non-legacy HPET
interrupt?

thanks
-john


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/