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

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Date:	Thu, 17 Sep 2009 00:21:11 +0400
From:	Sergei Shtylyov <sshtylyov@...mvista.com>
To:	Steve Chen <schen@...sta.com>
Cc:	Krzysztof Halasa <khc@...waw.pl>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	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

Hello.

Steve Chen wrote:

>>> +config OLD_CPU_DELAY
>>> +	depends on CPU_32v3 || CPU_32v4 || CPU_32v4T
>>> +	bool "Accurate delays for some older CPUs"
>>> +	def_bool n
>>> +	help
>>> +	  Try enable this if observing longer than expected delays and need
>>> +	  more accuracy.  May cause instability in some CPUs.
>>> +
>>>       
>> There is still this uncertain "accurate" in the text. Why don't just
>>
>> +	bool "Different delay() code for some older CPUs"
>>     
>
> Sounds good.  I also update text under help to better quantify
> "accuracy".  Updated patch below.  Separately, as Russel pointed out,
> this should only be done by experienced people, so we even bother with
> this patch since the only people should touch this are the people who
> knows all the details.
>
> Document #if 0 code block in delay.S and make it selectable for compile.
>
> Signed-off-by: Steve Chen <schen@...sta.com>
>
> ---
>
>  arch/arm/Kconfig     |    8 ++++++++
>  arch/arm/lib/delay.S |    2 +-
>  2 files changed, 9 insertions(+), 1 deletions(-)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index aef63c8..ca8d535 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -813,6 +813,14 @@ config ARM_ERRATA_460075
>  	  ACTLR register. Note that setting specific bits in the ACTLR
> register
>  	  may not be available in non-secure mode.
>  
> +config OLD_CPU_DELAY
> +	depends on CPU_32v3 || CPU_32v4 || CPU_32v4T
> +	bool "Different delay() code for some older CPUs"
> +	def_bool n
> +	help
> +	  Try enable this if observing longer than expected delays.  This code
>   

   Only "enabling"... ;-)

WBR, Sergei


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