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

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Message-ID: <20090915104919.GE19989@elf.ucw.cz>
Date:	Tue, 15 Sep 2009 12:49:20 +0200
From:	Pavel Machek <pavel@....cz>
To:	Felipe Contreras <felipe.contreras@...il.com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Jamie Lokier <jamie@...reable.org>,
	Marek Vasut <marek.vasut@...il.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm: remove unused code in delay.S

On Tue 2009-09-15 13:47:01, Felipe Contreras wrote:
> On Tue, Sep 15, 2009 at 1:37 PM, Pavel Machek <pavel@....cz> wrote:
> >
> >> >> > Because then you get it whenever you configure for V4 as the lowest
> >> >> > denominator CPU, which leads to the buggy behaviour on better CPUs.
> >> >> > It's far better to leave it as is and just accept that the old CPUs
> >> >> > will have longer than necessary delays.  If people really really
> >> >> > care (and there's likely to only be a small minority of them now)
> >> >> > changing the '0' to a '1' is a very simple change for them to carry
> >> >> > in their local tree.  Unlike getting the right unrolling etc.
> >> >>
> >> >> Well, they can also 'git revert' this patch. If somebody really cares
> >> >> I think they should shout now and provide a better patch, otherwise
> >> >> this one should be merged.
> >> >
> >> > On the other hand, having the code there as it currently stands is not
> >> > harmful in any way, so leaving it there is just as easy.
> >>
> >> It makes the code less understandable. I'm not sure about linux's
> >> practices, but an #if 0 generally means somebody is being lazy.
> >
> > Not in this case, as you was explained to you. You may want to add
> > explaining comment above #if 0....
> 
> Yes, but I've no idea in which situations somebody might want to
> enable that code. Old chips? Which old chips?

If you udelay() produces too long delays, as was explained in the thread. 
									Pavel
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