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

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Date:	Tue, 15 Sep 2009 14:20:00 +0300
From:	Felipe Contreras <felipe.contreras@...il.com>
To:	Pavel Machek <pavel@....cz>
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, Sep 15, 2009 at 1:49 PM, Pavel Machek <pavel@....cz> wrote:
> 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.

Yeah, on "older CPUs", and what constitutes an "older CPU" has not been defined.

-- 
Felipe Contreras
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