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SubjectRe: [RFC PATCH 5/5] arm64: qcom: add cpu operations
Date
On Tuesday 14 April 2015 17:29:53 Mark Rutland wrote:
>
> > +static int msm_cpu_boot(unsigned int cpu)
> > +{
> > + int ret = 0;
> > +
> > + if (per_cpu(cold_boot_done, cpu) == false) {
> > + ret = msm_unclamp_secondary_arm_cpu(cpu);
> > + if (ret)
> > + return ret;
> > + per_cpu(cold_boot_done, cpu) = true;
> > + }
> > + return secondary_pen_release(cpu);
> > +}
>
> Ah, so cold_boot_done is for pseudo-hotplug. Absolute NAK to that.
>
> The only thing this gives you over spin-table is one-time powering up of
> the CPUs that can be performed prior to entry to Linux. If you do that,
> you can trivially share the spin-table code by setting each CPU's
> enable-method to "spin-table".
>
> That won't give you cpuidle or actual hotplug. For those you'll need
> PSCI.

Maybe a way out for the broken firmware is to have a custom boot wrapper
that gets distributed separately and that uses the normal spin-table
API. We've done similar things on arch/arm/mach-sunxi for boot loaders
that are just too different from what we expect.

Once someone implements a proper loader, they could skip that extra
wrapper.

Arnd


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