linux-kernel - Re: [RFC PATCH 3/5] arm64: introduce CPU_OF

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Date:	Tue, 14 Apr 2015 16:52:14 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Kumar Gala <galak@...eaurora.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"arm@...nel.org" <arm@...nel.org>,
	Abhimanyu Kapur <abhimany@...eaurora.org>
Subject: Re: [RFC PATCH 3/5] arm64: introduce CPU_OF_TABLES for cpu ops
 selection

On Thu, Apr 09, 2015 at 10:17:06PM +0100, Arnd Bergmann wrote:
> On Thursday 09 April 2015 12:37:09 Kumar Gala wrote:
> > @@ -67,4 +67,9 @@ extern const struct cpu_operations *cpu_ops[NR_CPUS];
> >  int __init cpu_read_ops(struct device_node *dn, int cpu);
> >  void __init cpu_read_bootcpu_ops(void);
> >  
> > +#define CPU_METHOD_OF_DECLARE(name, __ops)                             \
> > +       static const struct cpu_operations *__cpu_method_table_##name   \
> > +       __used __section(__cpu_method_of_table)                         \
> > +       = __ops;
> > +
> >  #endif /* ifndef __ASM_CPU_OPS_H */
> > 
> 
> I'd rather not add this, to avoid giving the appearance that platforms
> can just add another one here.

Likewise.

SMP bringup is always hairy, and giving the appearance that such code
should be hidden away somewhere (and missing critical review) is a bad
idea.

While this seemed like a good idea in the past for 32-bit, we've only
seen marginal decoupling, and very little in the way of actual semantics
defined for the enable-methods. Which effectively spreads implementation
details further rather than separating them from the interface.

Mark.
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