linux-kernel - Re: [RFC/PATCH] arm: do not skip SMP init calls on SMP_ON

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Date:	Mon, 23 Nov 2015 15:47:34 +0300
From:	Nikita Yushchenko <nyushchenko@....rtsoft.ru>
To:	Vladimir Murzin <vladimir.murzin@....com>
CC:	Russell King - ARM Linux <linux@....linux.org.uk>,
	kuznetsovg@....rtsoft.ru, Ian Campbell <ian.campbell@...rix.com>,
	Mason <slash.tmp@...e.fr>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Will Deacon <will.deacon@....com>,
	Paul Kocialkowski <contact@...lk.fr>,
	linux-kernel@...r.kernel.org,
	Masahiro Yamada <yamada.m@...panasonic.com>,
	Pavel Machek <pavel@....cz>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC/PATCH] arm: do not skip SMP init calls on SMP_ON_UP case

>>>>> 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?..

Just booted mainline...  unline linux-imx, it does not try to init cpu1.

However, imx6dl.dtsi from mainline also has both cpu@0 and cpu@1

So missing piece in linux-imx is elsewhere :(

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