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

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Date:	Mon, 2 Jun 2014 12:27:50 +0200
From:	Antoine Ténart 
	<antoine.tenart@...e-electrons.com>
To:	Andrew Lunn <andrew@...n.ch>
Cc:	Antoine Ténart 
	<antoine.tenart@...e-electrons.com>,
	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 12:03:32PM +0200, Andrew Lunn wrote:
> 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?
> 
> 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?

I actually don't have information about this. For now let's assume the
boot loader has powered on the CPUs.

Antoine

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