linux-kernel - Re: [PATCH 2/9] ARM64: get rid of arch_cpu_idle

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Message-ID: <20140127155755.GH32608@arm.com>
Date:	Mon, 27 Jan 2014 15:57:55 +0000
From:	Catalin Marinas <catalin.marinas@....com>
To:	Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:	Russell King <linux@....linux.org.uk>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mundt <lethal@...ux-sh.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-sh@...r.kernel.org" <linux-sh@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>
Subject: Re: [PATCH 2/9] ARM64: get rid of arch_cpu_idle_prepare()

On Mon, Jan 27, 2014 at 03:51:02PM +0000, Nicolas Pitre wrote:
> On Mon, 27 Jan 2014, Catalin Marinas wrote:
> 
> > On Mon, Jan 27, 2014 at 06:08:17AM +0000, Nicolas Pitre wrote:
> > > ARM and ARM64 are the only two architectures implementing
> > > arch_cpu_idle_prepare() simply to call local_fiq_enable().
> > > 
> > > We have secondary_start_kernel() already calling local_fiq_enable() and
> > > this is done a second time in arch_cpu_idle_prepare() in that case. And
> > > enabling FIQs has nothing to do with idling the CPU to start with.
> > > 
> > > So let's introduce init_fiq_boot_cpu() to take care of FIQs on the boot
> > > CPU and remove arch_cpu_idle_prepare(). This is now done a bit earlier
> > > at late_initcall time but this shouldn't make a difference in practice
> > > given that FIQs are not currently used on ARM64.
> > > 
> > > Signed-off-by: Nicolas Pitre <nico@...aro.org>
> > 
> > For arm64, we could simply remove any reference to FIQs. I'm not aware
> > of anyone using them.
> 
> OK. What if I sumply remove arch_cpu_idle_prepare() and let you do the 
> remove the rest?
> 
> IMHO I'd simply remove local_fiq_{enable/disable}() from 
> arm64/kernel/smp.c and leave the infrastructure in place in case someone 
> needs it eventually.  In which case I could include that into my patch 
> as well.

Sounds good. We can keep the local_fiq_*() functions but remove about 4
calling sites (process.c and smp.c) until needed.

Thanks.

-- 
Catalin
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