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Subject: RE: [PATCH V4 3/4] ARM: Xilinx: base header files and assembly macros
Date: Mon, 21 Feb 2011 08:04:38 -0700
In-Reply-To: <201102211548.36296.arnd@arndb.de>
Thread-Topic: [PATCH V4 3/4] ARM: Xilinx: base header files and assembly macros
Thread-Index: AcvR1ptMe06Zsr34TamLqiu8JvUIPwAAR7Tw
References: <1298052881-14591-1-git-send-email-john.linn@xilinx.com><201102210936.42098.arnd@arndb.de><c3cdf33d-2163-4417-bc64-7637f5c211e0@VA3EHSMHS021.ehs.local> <201102211548.36296.arnd@arndb.de>
From: John Linn <John.Linn@xilinx.com>
To: Arnd Bergmann <arnd@arndb.de>
CC: <linux@arm.linux.org.uk>, <catalin.marinas@arm.com>,
        <glikely@secretlab.ca>, <linux-kernel@vger.kernel.org>,
        <jamie@jamieiles.com>, <linux-arm-kernel@lists.infradead.org>
Message-ID: <6c1f68a4-997a-4a8d-882e-5840e8bdf7af@VA3EHSMHS004.ehs.local>
Sender: linux-kernel-owner@vger.kernel.org
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> -----Original Message-----
> From: linux-arm-kernel-bounces@lists.infradead.org [mailto:linux-arm-
> kernel-bounces@lists.infradead.org] On Behalf Of Arnd Bergmann
> Sent: Monday, February 21, 2011 7:49 AM
> To: John Linn
> Cc: linux@arm.linux.org.uk; catalin.marinas@arm.com;
> glikely@secretlab.ca; linux-kernel@vger.kernel.org;
> jamie@jamieiles.com; linux-arm-kernel@lists.infradead.org
> Subject: Re: [PATCH V4 3/4] ARM: Xilinx: base header files and
assembly
> macros
> 
> On Monday 21 February 2011, John Linn wrote:
> > > It would be better if you could avoid introducing new uses of
> > > CLOCK_TICK_RATE, because that will have to be removed before we
can
> > > move to a real multi-platform kernel. For instance, you can put
> > > PERIPHERAL_CLOCK_RATE in a hardware specific header and put a
bogus
> > > definition for CLOCK_TICK_RATE into timex.h
> >
> > Hi Arnd,
> >
> > I can remove the use of it from my timer code, but I still see
> > CLOCK_TICK_RATE
> > being used in linux/jiffies.h.
> >
> > I tried removing it and got build errors.  Am I missing something
> there?
> >
> 
> You still need to have some definition for CLOCK_TICK_RATE to make
> the jiffies code compile, but the actual value no longer matters.

I see. Now that I re-read your last response I get that from it.

> 
> Traditionally, this was the i386-style PIT timer frequency of 11.93
MHz
> for some things and the actual timer frequency for other things.
> The timer code tries to correct the jiffies value based on difference
> between the intended HZ frequency (100, 250 or 1000) and the actual
> on (something very close to that, but not exact).
> 
> You can e.g. set it to (100 * HZ) to make something up that won't
> hurt in that calculation.
> 

Gotcha. I now understand to stay away from using CLOCK_TICK_RATE.

Sounds like it's worth a comment in mach/timex.h that says it's not 
really used as it seems a bit misleading for others.

Thanks,
John

> 	Arnd
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel


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