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

Jisheng Zhang
2014-06-03T06:22:38Z

Hi Andrew, Antoine,

On Mon, 2 Jun 2014 03:27:50 -0700
Antoine Ténart <antoine.tenart@free-electrons.com> wrote:

> 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.
>

We don't support independently power off cpu on BG2 and BG2Q in linux kernel.
So we can assume that bootloader has powered on the CPUs