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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Thu, 17 Oct 2019 21:20:01 +0200
Message-ID: <CAJZ5v0h7+53bT4oF109b-ah3wjFNYxz+PNr7DOBQ7rpRKbtGWQ@mail.gmail.com>
Subject: Re: [PATCH] cpuidle-haltpoll: make haltpoll aware of 'idle=' override
To:     Zhenzhong Duan <zhenzhong.duan@oracle.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Linux PM <linux-pm@vger.kernel.org>,
        Marcelo Tosatti <mtosatti@redhat.com>,
        Joao Martins <joao.m.martins@oracle.com>
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On Thu, Oct 17, 2019 at 2:41 AM Zhenzhong Duan
<zhenzhong.duan@oracle.com> wrote:
>
> Currenly haltpoll isn't aware of the 'idle=' override, the priority is
> 'idle=poll' > haltpoll > 'idle=halt'. When 'idle=poll' is used, cpuidle
> driver is bypassed but current_driver in sys still shows 'haltpoll'.
>
> When 'idle=halt' is used, haltpoll take precedence and make 'idle=halt'
> no effect.
>
> Add a check to not load haltpoll driver if there is 'idle='

OK

> and haltpoll
> is built in. If haltpoll is built as a module, still give a chance for
> admin to use it despite 'idle='.

Why exactly?  Do you have any particular use case in mind?

Otherwise I'd prefer the behavior to be consistent regardless of
whether or not it is a module..