linux-kernel - Re: [PATCH 1/5] ARM: berlin: add SMP support

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Message-ID: <20140602100332.GH28090@lunn.ch>
Date:	Mon, 2 Jun 2014 12:03:32 +0200
From:	Andrew Lunn <andrew@...n.ch>
To:	Antoine Ténart 
	<antoine.tenart@...e-electrons.com>
Cc:	Andrew Lunn <andrew@...n.ch>, sebastian.hesselbarth@...il.com,
	thomas.petazzoni@...e-electrons.com, zmxu@...vell.com,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	alexandre.belloni@...e-electrons.com, jszhang@...vell.com,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/5] ARM: berlin: add SMP support

On Mon, Jun 02, 2014 at 12:00:48PM +0200, Antoine Ténart wrote:
> Hi Andrew,
> 
> On Mon, Jun 02, 2014 at 11:47:15AM +0200, Andrew Lunn wrote:
> > On Mon, Jun 02, 2014 at 11:21:02AM +0200, Antoine Ténart wrote:
> > > +
> > > +static inline void berlin_reset_cpu(unsigned int cpu)
> > > +{
> > > +	u32 val;
> > > +
> > > +	val = readl(cpu_ctrl + CPU_RESET);
> > > +	val |= BIT(cpu_logical_map(cpu));
> > > +	writel(val, cpu_ctrl + CPU_RESET);
> > > +}
> > 
> > Is this performing a reset on the CPU, or is it taking it out of reset?
> > 
> > If you are going to implement CPU hotplug at some point, you are going
> > to want to be able to put the CPU into reset, i.e. power it off, and
> > take it out of reset, i.e. power it on and getting it running. So it
> > might help if we get these function names clear now.
> 
> It is performing a reset on the CPU. berlin_perform_reset_cpu() then?

Yes, that would be better.

What happens if the CPU is powered off? Will a reset power it on?  Or
are you assuming the boot loader has powered it on?

    Andrew
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