linux-kernel - Re: [PATCH v2] ARM: smp: Only expose /sys/.../cpuX/online if hotpluggable

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Date:	Fri, 13 Feb 2015 16:01:43 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Magnus Damm <magnus.damm@...il.com>
CC:	Simon Horman <horms@...ge.net.au>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Mark Rutland <mark.rutland@....com>,
	Nicolas Pitre <nico@...aro.org>,
	Dave Martin <Dave.Martin@....com>,
	SH-Linux <linux-sh@...r.kernel.org>
Subject: Re: [PATCH v2] ARM: smp: Only expose /sys/.../cpuX/online if hotpluggable

On 02/13/15 15:01, Russell King - ARM Linux wrote:
> On Fri, Feb 13, 2015 at 09:44:50PM +0000, Magnus Damm wrote:
>> Also, based on the comment in mcpm_cpu_can_disable() it looks like the
>> PSCI hook may be executed once only with your change in place?
>> Hopefully PSCI is OK not being invoked for every CPU shutdown.
> This is why I've said (in the parent thread) that I'm not happy to
> apply this patch.  Mark Rutland has indicated that he has MCPM cases
> where the CPUs which can be disabled changes dynamically according
> to the secure firmware requirements, and ripping out todays
> infrastructure in light of that, only to have to add it back again
> later makes no sense.

Putting it back is not hard. And the infrastructure is not currently
used for these purposes so renaming it is appropriate. I can leave it in
place if you like, i.e. make a new op for cpu_can_disable and repoint
mcpm's mcpm_cpu_disable() at it. Then when mcpm gets migrate support it
can actually implement a cpu_disable op.

>
> However, cleaning things up by removing unnecessary cpu_disable
> methods is a good thing to do irrespective of that.
>

That's fine I can split it out.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

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