linux-kernel - Re: [RFC/PATCH 1/2] cpuidle: Allow idle-states to be disabled at start

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Date:   Wed, 24 Aug 2016 17:06:31 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Balbir Singh <bsingharora@...il.com>,
        "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Michael Neuling <michael.neuling@....ibm.com>,
        Paul Mackerras <paulus@...ba.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Anton Blanchard <anton@...ba.org>, linux-pm@...r.kernel.org
Subject: Re: [RFC/PATCH 1/2] cpuidle: Allow idle-states to be disabled at
 start

On 08/24/2016 04:48 PM, Balbir Singh wrote:
> 
> 
> On 25/08/16 00:44, Daniel Lezcano wrote:
>> On 08/19/2016 12:26 AM, Gautham R. Shenoy wrote:
>>> From: "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
>>>
>>> Currently all the idle states registered by a cpu-idle driver are
>>> enabled by default. This patch adds a mechanism which allows the
>>> driver to hint if an idle-state should start in a disabled state. The
>>> cpu-idle core will use this hint to appropriately initialize the
>>> usage->disable knob of the CPU device idle state.
>>
>> Why do you need to do that ?
>>
> 
> I think patch 2/2 explains the reason as it uses this infrastructure

Ok, let me elaborate the question, I was not clear.

Why the userspace can't setup the system environment at boot time by
disabling the state instead of adding extra code to disable it at boot
time in the kernel and then re-enable it from userspace ?

  -- Daniel


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