linux-kernel - Re: [PATCH] arm: remove unused code in delay.S

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Message-ID: <20090916134721.GA11218@n2100.arm.linux.org.uk>
Date:	Wed, 16 Sep 2009 14:47:21 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Krzysztof Halasa <khc@...waw.pl>
Cc:	Steve Chen <schen@...sta.com>,
	Felipe Contreras <felipe.contreras@...il.com>,
	Jamie Lokier <jamie@...reable.org>,
	linux-kernel@...r.kernel.org, Marek Vasut <marek.vasut@...il.com>,
	Pavel Machek <pavel@....cz>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm: remove unused code in delay.S

On Tue, Sep 15, 2009 at 11:04:37PM +0200, Krzysztof Halasa wrote:
> Steve Chen <schen@...sta.com> writes:
> 
> > +config OLD_CPU_DELAY
> > +	depends on CPU_32v3 || CPU_32v4 || CPU_32v4T
> > +	bool "Accurate delays"
> > +	def_bool n
> > +	help
> > +	  Enable if observing longer than expected delays and need more
> > +	  accuracy.  This only applies to older CPUs.
> > +
> 
> If it's that simple then why not enable the extra delay code
> unconditionally when compiling for those CPUs?

Because it's really not that clear cut.  Eg, ARM610 and ARM710 work
better with it, but StrongARM suffers from delays being too short.
Having a kernel configured for all those processors used to be common
(since the Acorn RiscPC had pluggable CPU cards, which could be one
of those processors.)

It's really something that only experienced people should worry
about, and not Joe "kernel-builder" Bloggs.
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