linux-kernel - Re: [PATCH] at91 pm: Compilation fix for at91sam926x

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Date:	Fri, 10 Aug 2007 09:12:35 +0200
From:	Hans-Jürgen Koch <hjk@...utronix.de>
To:	linux-arm-kernel@...ts.arm.linux.org.uk
Cc:	"Ulf Samuelsson" <ulf@...el.com>,
	"Marc Pignat" <marc.pignat@...s.ch>, andrew@...people.com,
	trivial@...nel.org, linux-kernel@...r.kernel.org,
	Andy Herzig <andrew.herzig@....com>
Subject: Re: [PATCH] at91 pm: Compilation fix for at91sam926x

Am Freitag 10 August 2007 00:15 schrieb Ulf Samuelsson:
> 
> > > +#if defined(CONFIG_ARCH_AT91RM9200)
> > >                         at91_sys_write(AT91_SDRAMC_SRR, 1);     /*
> > > self-refresh mode */
> 
> > Why don't use:
> > if (cpu_is_at91rm9200())
> > at91_sys_write(AT91_SDRAMC_SRR, 1);
> 
> What is the benefit?
> Will the optimizer remove the code if the CPU is not the at91rm9200?

No, it won't. cpu_is_something() is intended for runtime decisions.
Remember that the purpose of this patch was to solve a compile time
issue (see subject). AT91_SDRAMC_SRR isn't defined properly for
non-9200 processors because they don't have that register. So we need
something like #ifdef to include this line only on 9200.

Hans
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