linux-kernel - Re: [PATCH 1/3] Add smp support for Allwinner A20(sunxi 7i).

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Date:	Mon, 23 Sep 2013 21:34:30 +0300
From:	"maxime.ripard@...e-electrons.com" <maxime.ripard@...e-electrons.com>
To:	cinifr <cinifr@...il.com>
Cc:	Ian Campbell <ijc@...lion.org.uk>,
	"linux-sunxi@...glegroups.com" <linux-sunxi@...glegroups.com>,
	"coosty@....com" <coosty@....com>,
	"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"pawel.moll@....co" <pawel.moll@....co>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>
Subject: Re: [PATCH 1/3] Add smp support for Allwinner A20(sunxi 7i).

Hi,

On Mon, Sep 23, 2013 at 10:43:55PM +0800, cinifr wrote:
> > In which case this kernel patch needs instead to speak the bootloader
> > wakeup protocol instead of speaking to the h/w directly like you've done
> > here, right?
> >
> > Or is it possible for the bootloader to set these things up and then put
> > the CPU back to sleep such that it both retains any settings and is
> > wakable by this patch? This code contains core resets and power control,
> > which makes me suspect not.
> 
> And I think secondary cpus  remains setting after h/w boot.
> >> > Wouldn't it be better to do all this stuff in the bootloader and
> >> either
> >> > implement PSCI or have the bootloader do the traditional holding pen
> >> and
> >> > mbox address thing?
> Uboot doesnot support PSCI, it use  traditional holding pen for sunxi
> platform now.
> 
> >> >
> >> I have modified uboot to set cntfrq and cntvoff in all smp cpus,and it
> >> works well. I guess kernel should believe all cpu should be all same
> >> when kernel boot. Bootloader should do it to ensure that.
> >
> > Yes, I think all CPUs must be in the same state at boot.
> >
> > But if you've done all that then what is this patch for?
> >
> > Do you have links to your u-boot patches?
> >
> > Ian.
> Yes, This is my patch for uboot.
> My working uboot code is in https://github.com/linux-sunxi/u-boot-sunxi.git
> Note this is only test patch. I have not commit it  formally for uboot.

Please do so. I'd like very much to avoid ending up in a situation where
we would break the mainline kernel for the A20, without any bootloader
we can point the users to to fix the issues.

Maxime

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

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