linux-kernel - Re: [PATCH 0/2] Fix secondary CPU boot for thumb2 kernels

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Message-ID: <20150129154624.GH8951@e104818-lin.cambridge.arm.com>
Date:	Thu, 29 Jan 2015 15:46:25 +0000
From:	Catalin Marinas <catalin.marinas@....com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	Russell King <linux@....linux.org.uk>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Kumar Gala <galak@...eaurora.org>
Subject: Re: [PATCH 0/2] Fix secondary CPU boot for thumb2 kernels

On Wed, Jan 28, 2015 at 08:22:41PM +0000, Stephen Boyd wrote:
> On 01/21/15 11:48, Stephen Boyd wrote:
> > Currently I can't boot up secondary CPUs on qcom platforms when I
> > compile the kernel for THUMB2 mode. This is because we always enter
> > the kernel in ARM mode regardless of what mode the kernel is compiled
> > for. This patchset adds a small wrapper to secondary_startup() called
> > secondary_startup_arm() that allows us to switch into THUMB2 mode if
> > we need to. If the kernel is compiled for ARM mode it shouldn't have
> > any effect.
> >
> > Stephen Boyd (2):
> >   ARM: Add a secondary_startup that assumes ARM mode
> >   ARM: qcom: Use secondary_startup_arm()
> >
> >  arch/arm/kernel/head.S       | 7 +++++++
> >  arch/arm/mach-qcom/platsmp.c | 4 ++--
> >  2 files changed, 9 insertions(+), 2 deletions(-)
> 
> Any comments here? Perhaps I can send this through the patch tracker?

FWIW, they look fine to me.

Acked-by: Catalin Marinas <catalin.marinas@....com>

I guess the reason it works fine on other platforms is because the
secondary start address we pass to firmware has bit 0 set and this
causes the jump to the kernel in Thumb-2 mode.

Catalin
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