linux-kernel - Re: [PATCH v4 10/10] ARM: sunxi: smp: Add initialization of CNTVOFF

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Date:   Mon, 19 Mar 2018 11:59:11 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Mylène Josserand <mylene.josserand@...tlin.com>
Cc:     Marc Zyngier <marc.zyngier@....com>, linux@...linux.org.uk,
        wens@...e.org, robh+dt@...nel.org, mark.rutland@....com,
        devicetree@...r.kernel.org, quentin.schulz@...tlin.com,
        linux-kernel@...r.kernel.org, clabbe.montjoie@...il.com,
        thomas.petazzoni@...tlin.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 10/10] ARM: sunxi: smp: Add initialization of CNTVOFF

On Sun, Mar 18, 2018 at 08:07:15PM +0100, Mylène Josserand wrote:
> Hello Mark,
> 
> Please, excuse me for this late answer and thank you for the review!
> 
> On Wed, 7 Mar 2018 12:18:33 +0000
> Marc Zyngier <marc.zyngier@....com> wrote:
> 
> > On 23/02/18 13:37, Mylène Josserand wrote:
> > > On Cortex-A7, the CNTVOFF register from arch timer is uninitialized.  
> > 
> > Only on A7? Is that specific to your platform?
> 
> I do not really know other Allwinner's platforms about this subject. At
> least, the sun9i-a80 which is a Cortex-a15/a7 does not need that but it
> is necessary for sun8i-a83t which is a cortex-a7. Maybe, Chen-Yu or
> Maxime could help us on it.

This is not related to the CPU.

On all the other SoCs but the A80 and the A83t, U-Boot will boot the
system in HYP, and while switching to non-secure will setup CNTVOFF on
the boot CPU.

On the A80 and A83t, U-Boot will execute the kernel in secure, it will
not switch to non-secure, and CNTVOFF will not be set on the boot CPU.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com