linux-kernel - Re: [PATCH 04/27] ARM: EXYNOS: Support secondary CPU boot of Exynos4212

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Date:	Fri, 11 Apr 2014 09:14:53 +0200
From:	Tomasz Figa <t.figa@...sung.com>
To:	Sangbeom Kim <sbkim73@...sung.com>,
	'Chanwoo Choi' <cw00.choi@...sung.com>,
	'Olof Johansson' <olof@...om.net>
Cc:	linux-samsung-soc@...r.kernel.org, hyunhee.kim@...sung.com,
	sw0312.kim@...sung.com, linux-kernel@...r.kernel.org,
	yj44.cho@...sung.com, inki.dae@...sung.com,
	kyungmin.park@...sung.com, kgene.kim@...sung.com,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 04/27] ARM: EXYNOS: Support secondary CPU boot of Exynos4212

Hi Sangbeom,

On 11.04.2014 08:04, Sangbeom Kim wrote:
> Hi,
> On 04/11/2014 2:14 PM, Chanwoo Choi wrote:
>
>>>>   {
>>>> -	exynos_smc(SMC_CMD_CPU1BOOT, cpu, 0, 0);
>>>> +	if (soc_is_exynos4212())
>>>> +		exynos_smc(SMC_CMD_CPU1BOOT, 0, 0, 0);
>>>> +	else
>>>> +		exynos_smc(SMC_CMD_CPU1BOOT, cpu, 0, 0);
>>>
>>> 	/* <explain why you need this special case on 4212> */
>>
>> It's better to ask system lsi person. We don't know it well.
>> I got the guide about secondary boot from system lsi.
>> But, this patch was completely tested.
>
> exynos_smc(SMC_CMD_CPU1BOOT, ...) is cpu hotplug SMC interface.
> Exynos4212 is dual core processor.
> Exynos4212 only have to boot cpu1 on smp boot.
> So, Second parameter of exynos_smc is fixed by 0 which means cpu1.
> It don't need to boot another cpu (ex. cpu2, cpu3 for quad core processor).
> But In case of quad core processor (ex. Exynos4412),
> It need to boot another cpu and specify parameter of booting core.
> As I know, Exynos3250 is dual core.
> So It can be included 1st condition too.

Is the smc API defined to ignore the first argument of SMC_CMD_CPU1BOOT 
command for dual core systems or it is defined as should be zero?

Best regards,
Tomasz
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