linux-kernel - Re: [PATCH] ARM: cpuidle: Support asymmetric idle definition

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Message-ID: <77a67a7d-4a0d-29b7-dee3-1584f2134309@linaro.org>
Date:   Thu, 1 Jun 2017 09:37:50 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     rjw@...ysocki.net, lorenzo.pieralisi@....com, leo.yan@...aro.org,
        "open list:CPUIDLE DRIVERS" <linux-pm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: cpuidle: Support asymmetric idle definition

On 31/05/2017 19:33, Sudeep Holla wrote:
> 
> 
> On 31/05/17 17:40, Daniel Lezcano wrote:
> 
>> Hi Sudeep, Lorenzo,
>>
>> I have been thinking and looking at the domain-idle-state and I don't
>> see an obvious connection between what is describing the power domain,
>> the cpu idle driver and what we are trying to achieve.
>>
> 
> I am not sure what you mean by *connection* above.
> 
> 1. With old flat list of idle states, we should get the cpumask sharing
>    the idle states from the phandle or something similar.
> 2. With new domain-idle-state and hierarchical DT binding, you just need
>    to infer that from the hierarchy.
> 
>> I would like to suggest something much more simple, register a cpuidle
>> driver per cpu, so every cpu can have its own idle definitions, that
>> should work for dynamiQ, smp and hmp. The impact on the driver will be
>> minimal.
>>
> 
> Sounds simple, but not sure if it's scalable on platforms with
> relatively large number of CPUs like 48 or 96(e.g. Cavium Thunder

I'm pretty sure it scales, we had the idle states per cpuidle devices
and nobody was complaining. But I agree it could be optimized.


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