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

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Date:	Wed, 15 Oct 2014 00:36:04 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Heiko Stübner <heiko@...ech.de>
Cc:	Doug Anderson <dianders@...omium.org>,
	Kever Yang <kever.yang@...k-chips.com>,
	Sonny Rao <sonnyrao@...omium.org>,
	Addy Ke <addy.ke@...k-chips.com>,
	Eddie Cai <cf@...k-chips.com>, Jianqun Xu <xjq@...k-chips.com>,
	han jiang <hj@...k-chips.com>,
	Tao Huang <huangtao@...k-chips.com>,
	linux-rockchip@...ts.infradead.org,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 4/6] ARM: rockchip: add basic smp support for rk3288

On Tue, Oct 14, 2014 at 11:23:40PM +0200, 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
> 
> 	read_cpuid_id() & ARM_CPU_PART_MASK
> 
> which in turn should mask the correct parts of the cpuid to match against 
> ARM_CPU_PART_CORTEX_A9 [0].

The clue is the deprecated message.  Clearly the original author did not
even build test their code, or if they did, they ignored the warnings.
Either way, that's a fairly worrying issue which raises the question:
how well was this code tested in the first place?

Note that the above quoted if() evaluates to always-false.

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