Re: [PATCH] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start

From: Chander Kashyap <chander.kashyap@linaro.org>
To: Doug Anderson <dianders@chromium.org>
Cc: Chander Kashyap <k.chander@samsung.com>,
	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>,
	"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>
Subject: Re: [PATCH] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start
Date: Mon, 16 Jun 2014 13:10:58 +0530	[thread overview]
Message-ID: <CANuQgHHf_NtL+-=1S14meyT8auBsh0kn6Zn+p6r==qAEgVG1UA@mail.gmail.com> (raw)
In-Reply-To: <CAD=FV=XkTSfHwt9Ekcy6TPGWJTJ49zMCOA9eaJVaq=q4u4Ri3Q@mail.gmail.com>

Hi Doug,

On 13 June 2014 20:40, Doug Anderson <dianders@chromium.org> wrote:
> 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).

Yes i agree with your point.
What i am saying is when there is full support for Exynos5420 in
mainline u-boot we need to take care for the mcpm_entry_point address.

>
> -Doug

-- 
with warm regards,
Chander Kashyap