linux-kernel - Re: [PATCH V3 7/8] ARM: cpuidle: Register per cpuidle device

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Date:	Mon, 23 Mar 2015 15:42:01 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"robherring2@...il.com" <robherring2@...il.com>,
	"arnd@...db.de" <arnd@...db.de>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"lina.iyer@...aro.org" <lina.iyer@...aro.org>,
	"sboyd@...eaurora.org" <sboyd@...eaurora.org>
Subject: Re: [PATCH V3 7/8] ARM: cpuidle: Register per cpuidle device

On 03/21/2015 09:35 PM, Lorenzo Pieralisi wrote:
> On Fri, Mar 20, 2015 at 11:44:00AM +0000, Daniel Lezcano wrote:
>> Some architectures have some cpus which does not support idle states.
>>
>> Let the underlying low level code to return -ENXIO when it is not
>> possible to set an idle state.
>
> Well, this is getting interesting. We are parsing possible CPUs to
> detect if they have common idle states in DT. If a CPU does not support
> idle states, the cpu node for that CPU should not define any idle
> state.
>
> The approach above will work with my heterogenous system patch, since
> the respective CPUidle driver mask will be created by parsing the DT
> idle states.
>
> http://www.spinics.net/lists/arm-kernel/msg403190.html
>
> In current approach if a "possible " CPU does not have idle states, we do
> not init CPUidle at all.
>
> So, to cut a long story short, what does "a cpu does not support idle
> states" mean ?
>
> Does it mean that firmware defines idle states for that CPU in DT but
> initializing them fail ?
>
> I am fine with this patch, but we need to define -ENXIO return properly.

Ok, I think that needs more discussion.

I will drop this patch from my patchset as we agreed on the other 
patches and resubmit.

   -- Daniel


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