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

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Message-ID: <20150625165741.GA10564@leverpostej>
Date:	Thu, 25 Jun 2015 17:57:42 +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 05:55:40PM +0100, Vitaly Andrianov wrote:
> 
> 
> On 06/25/2015 12:13 PM, Mark Rutland wrote:
> > 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
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> >
> Thanks Mark,
> 
> I need rework and re-test the patch.
> One more question. Shall I post the dts related commit, which add PSCI 
> command together with this commit? Or it may be posted later independently?

The DTS and Kconfig changes can be seaprate patches, but they'll need to
go through at the same time.

You shouldn't need to add any platform code, but you may need to add a
some guards to support existing (non-PSCI) systems and PSCI systems with
the same kernel if your board code unconditionally pokes hardware that
the PSCI implementation will be in charge of (with PSCI the kernel
should no nothing about said hardware).

Thanks,
Mark.
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