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Date: Fri, 13 Jun 2014 08:10:18 -0700
Message-ID: <CAD=FV=XkTSfHwt9Ekcy6TPGWJTJ49zMCOA9eaJVaq=q4u4Ri3Q@mail.gmail.com>
Subject: Re: [PATCH] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start
From: Doug Anderson <dianders@chromium.org>
To: Chander Kashyap <k.chander@samsung.com>
Cc: Kukjin Kim <kgene.kim@samsung.com>,
        Nicolas Pitre <nicolas.pitre@linaro.org>,
        "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
        "linux@arm.linux.org.uk" <linux@arm.linux.org.uk>,
        Kevin Hilman <khilman@linaro.org>,
        Andrew Bresticker <abrestic@chromium.org>,
        Inderpal Singh <inderpal.s@samsung.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Chander Kashyap <chander.kashyap@linaro.org>,
        "olof@lixom.net" <olof@lixom.net>, Tushar Behera <trblinux@gmail.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Thomas Abraham <thomas.ab@samsung.com>,
        Abhilash Kesavan <a.kesavan@samsung.com>,
        Javier Martinez Canillas <javier.martinez@collabora.co.uk>,
        "linux-samsung-soc@vger.kernel.org" 
	<linux-samsung-soc@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org

Chander,

On Fri, Jun 13, 2014 at 4:54 AM, Chander Kashyap <k.chander@samsung.com> wrote:
> This patch is effectively changing the mcpm_entry_point address from
> nsbase + 0x1c to nsbase + 0x8
>
> Hence while integrating with mainline u-boot we need to take care for
> new mcpm_entry_point address.
>
> With Chromebook it works straightforward.

Can you explain more and point to the code that is using the nsbase +
0x1c?  Specifically the only code I see that uses the nsbase + 0x1c is
the code that is located at nsbase, which is the code we're
overwriting here.  I'd imagine you're using U-Boot code that looks
something like the bits that start at code_base here:

https://chromium.googlesource.com/chromiumos/third_party/u-boot/+/ce358daf5069f1dc145b0f9d403cfbb028271807/arch/arm/cpu/armv7/exynos/lowlevel.S

With my kernel change you can completely eliminate U-Boot's
installation of this code (or keep it, it makes no difference).

-Doug
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