linux-kernel - Re: [PATCH 4/4] arm: psci: add cpuidle

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Date:	Wed, 8 Jul 2015 19:38:42 +0800
From:	Jisheng Zhang <jszhang@...vell.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	<will.deacon@....com>, <mark.rutland@....com>,
	<daniel.lezcano@...aro.org>, <Catalin.Marinas@....com>,
	<Lorenzo.Pieralisi@....com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] arm: psci: add cpuidle_ops support

Dear Russell,

On Wed, 8 Jul 2015 11:34:29 +0100
Russell King - ARM Linux <linux@....linux.org.uk> wrote:

> On Wed, Jul 08, 2015 at 06:13:37PM +0800, Jisheng Zhang wrote:
> > This patch implements cpuidle_ops using psci. After this patch, we can use
> > cpuidle-arm.c with psci backend for both arm and arm64.
> 
> I really don't see the point of most of the patches in this series.
> 
> To summarise, what you're doing is:
> 
> 1. Renaming arch/arm/kernel/psci_smp.c to arch/arm/kernel/psci.c
> 2. Adding a #ifdef CONFIG_SMP around _all_ the code in psci.c
> 3. Adding cpuidle code with an #ifdef CONFIG_CPU_IDLE around all the
>    CPU idle code.
> 
> So, we end up with a file which contains:
> 
> /*
>  header
>  */
> #include statements
> 
> /*
>  some commentry relevant to SMP code
>  */
> #ifdef CONFIG_CPU_IDLE
> ... cpu idle code ...
> #endif
> #ifdef CONFIG_SMP
> ... smp code ...
> #endif
> 
> which (a) is a mess, and (b) is unnecessary.  The only relevant bits which
> are shared are the #include statements.
> 
> Please try this alternative approach:
> 
> 1. Leave psci_smp.c alone.
> 2. Add arch/arm/kernel/psci_cpuidle.c containing the #include statements
>    you need, and the CPU idle code.
> 
> I think such an approach will reduce your patch series to two patches,
> one moving the ARM64 code, and one adding the cpuidle code.
> 

Good idea! Will refine the patches as you suggested.

Thanks a lot for your review,
Jisheng
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