linux-kernel - Re: [PATCH v4 4/6] ARM: rockchip: add basic smp support for rk3288

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Date:	Tue, 14 Oct 2014 23:49:07 -0700
From:	Kever Yang <kever.yang@...k-chips.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Heiko Stübner <heiko@...ech.de>,
	Doug Anderson <dianders@...omium.org>,
	Tao Huang <huangtao@...k-chips.com>,
	Addy Ke <addy.ke@...k-chips.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-rockchip@...ts.infradead.org,
	Jianqun Xu <xjq@...k-chips.com>, Eddie Cai <cf@...k-chips.com>,
	han jiang <hj@...k-chips.com>,
	Sonny Rao <sonnyrao@...omium.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 4/6] ARM: rockchip: add basic smp support for rk3288

Russell,

On 10/14/2014 04:37 PM, Russell King - ARM Linux wrote:
> On Tue, Oct 14, 2014 at 02:50:07PM -0700, Kever Yang wrote:
>> Heiko,
>>
>> On 10/14/2014 02:23 PM, Heiko Stübner wrote:
>>> Am Dienstag, 14. Oktober 2014, 13:24:03 schrieb Doug Anderson:
>>>> Kever,
>>>>
>>>> On Mon, Oct 13, 2014 at 1:12 PM, Kever Yang <kever.yang@...k-chips.com>
>>> wrote:
>>>>> +       /*
>>>>> +        * We need to soft reset the cpu when we turn off the cpu power
>>>>> domain, +        * or else the active processors might be stalled when
>>>>> the individual +        * processor is powered down.
>>>>> +        */
>>>>> +       if (read_cpuid_part_number() != ARM_CPU_PART_CORTEX_A9) {
>>>> I haven't done a full review of this patch, but it seems unlikely that
>>>> your uses of read_cpuid_part_number() and read_cpuid_part() in this
>>>> patch are correct.  You use both functions and in both cases compare
>>>> the results to ARM_CPU_PART_CORTEX_A9.
>>> I think read_cpuid_part() would be the correct one, as it does
>> You are right, read_cpuid_part() is correct one on kernel next,
>> I mix up 3.14 kernel and next tree, only read_cpuid_part_number() is
>> available
>> in 3.14 kernel.
>>
>> I will correct it in my next version, any other changes needed for new
>> version?
> You need to at the _very_ _minimum_ build test your code against a
> recent kernel, and preferably test it to make sure that it works as
> you intend.
Thanks for you advice, I'll be more careful next time.

I'm sorry for not test this patch with rk3188(A9 based) board,
I do have test it on top of kernel next with my rk3288 evb(not A9 based),
and I didn't get any warning for read_cpuid_part_number()
during building the image.

- Kever
>
> Developing on such an old kernel version, and hoping that the code is
> going to be correct for later kernels isn't a nice idea.
>

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