linux-kernel - Re: [PATCH] keystone: psci: adds cpu

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Date:	Thu, 25 Jun 2015 17:13:08 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Vitaly Andrianov <vitalya@...com>
Cc:	santosh shilimkar <santosh.shilimkar@...cle.com>,
	"ssantosh@...nel.org" <ssantosh@...nel.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>
Subject: Re: [PATCH] keystone: psci: adds cpu_die implementation

On Thu, Jun 25, 2015 at 05:01:36PM +0100, Vitaly Andrianov wrote:
> 
> 
> On 06/25/2015 10:59 AM, santosh shilimkar wrote:
> > On 6/25/2015 7:45 AM, Mark Rutland wrote:
> >> Hi,
> >>
> >> On Thu, Jun 25, 2015 at 03:02:50PM +0100, Vitaly Andrianov wrote:
> >>> This commit add cpu_die implementation using psci api
> >>
> >> I don't understand. If you have a PSCI implementation, it should be
> >> sufficient to have a PSCI node (and enable-method) in your DT, and the
> >> generic code will be used. Nothing should be required in your board
> >> code.
> >>
> >> You should also use CPU_ON to bring secondaries online rather than
> >> mixing up PSCI and platform-specific mechanisms.
> >>
> > Good point about CPU_ON. We need that as well.
> >
> Does it mean that keystone_defconfig must always have CONFIG_HOTPLUG_CPU 
> and CONFIG_ARM_PSCI enabled?

No.

You need CONFIG_ARM_PSCI for PSCI CPU_ON. Without CONFIG_HOTPLUG_CPU,
you'll get PSCI CPU_ON but not PSCI CPU_OFF.

> What is if someone doesn't want to have HOTPLUG_CPU?

Then you don't get PSCI CPU_OFF, but can still have PSCI CPU_ON.

Only the portions of the PSCI code required for turning CPUs off are
dependent on HOTPLUG_CPU.

> How he can boot secondary CPU w/o platform-specific mechanizm?

By using PSCI CPU_ON.

Thanks,
Mark
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