Message-ID: <5653099A.7020604@dev.rtsoft.ru>
Date: Mon, 23 Nov 2015 15:42:02 +0300
From: Nikita Yushchenko <nyushchenko@dev.rtsoft.ru>
Organization: RTSoft Software Development Center
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To: Vladimir Murzin <vladimir.murzin@arm.com>
CC: Russell King - ARM Linux <linux@arm.linux.org.uk>,
        kuznetsovg@dev.rtsoft.ru, Ian Campbell <ian.campbell@citrix.com>,
        Mason <slash.tmp@free.fr>, Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Will Deacon <will.deacon@arm.com>,
        Paul Kocialkowski <contact@paulk.fr>, linux-kernel@vger.kernel.org,
        Masahiro Yamada <yamada.m@jp.panasonic.com>,
        Pavel Machek <pavel@ucw.cz>, linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC/PATCH] arm: do not skip SMP init calls on SMP_ON_UP case
References: <1448279946-19975-1-git-send-email-nyushchenko@dev.rtsoft.ru> <20151123120317.GN8644@n2100.arm.linux.org.uk> <5653015C.4020405@dev.rtsoft.ru> <56530769.4030403@arm.com>
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>>>> While running an imx6s boasrd, I got following message in boot log:
>>>>
>>>> [    0.032414] CPU1: failed to boot: -38
>>>>
>>>> This looked strange: imx6s is singe-core and kernel perfectly knows
>>>> that. However, for some reason it tries to initialize CPU 1?
>>>>
>>>> I found this to be caused by
>>>> - CONFIG_SMP_ON_UP successfully detects that system is single core,
>>>> - this causes is_smp() to return false,
>>>> - this causes setup_arch() to skip smp_init_cpus() call,
>>>> - this skips board-specific code that sets cpu_possible mask.
>>>
>>> Right, so you should end up with the possible and present masks
>>> containing just one CPU, which should prevent the kernel trying to
>>> bring any secondary CPUs online.
>>
>> Kernel that is running here still tries to init CPU 1 for some reason.
> 
> I *guess* cpus node [1] in your dts has more than one cpu entry, could
> you check please?

Indeed looks so:

# ls /proc/device-tree/cpus
#address-cells  #size-cells  cpu@0  cpu@1  name

But my custom device tree just includes imx6dl.dtsi

So it is imx6dl.dtsi in linux-imx tree broken?..


Still, if I apply change from the patch, issue diappears, since in this
case imx_smp_init_cpus() gets called and initializes possible_cpu mask
properly.
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