linux-kernel - Re: [PATCH v2 2/2] ARM: at91: pm: switch to the PIE infrastructure

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Message-ID: <20160629075714.GP29249@piout.net>
Date:	Wed, 29 Jun 2016 09:57:14 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Alexander Stein <alexander.stein@...tec-electronic.com>
Cc:	linux-kernel@...r.kernel.org,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org,
	Dave Martin <Dave.Martin@....com>,
	Doug Anderson <dianders@...omium.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Nicolas Ferre <nicolas.ferre@...el.com>
Subject: Re: [PATCH v2 2/2] ARM: at91: pm: switch to the PIE infrastructure

On 29/06/2016 at 08:12:21 +0200, Alexander Stein wrote :
> > +#if defined(CONFIG_CPU_V7)
> > +	dsb();
> > +	wfi();
> > +#else
> > +	asm volatile ("mcr	p15, 0, %0, c7, c0, 4" \
> > +		      : : "r" (0) : "memory");
> > +#endif
> 
> Why not defining wfi() for __LINUX_ARM_ARCH__ < 7 as it is done for dsb() and 
> friends in arch/arm/include/asm/barrier.h? So you can get rid of that #if 
> completly.

Well, Russell said it was not useful because "there's no architected WFI
instruction which doesn't have CPU specific issues (hence why we have
cpu_do_idle() to abstract that)"

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com