linux-kernel - Re: [PATCH] powerpc: Enable generic cpu idle-loop

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Message-ID: <875y5cwqdb.fsf@mail.lhotse>
Date:   Fri, 18 Aug 2023 21:18:24 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Vaibhav Jain <vaibhav@...ux.ibm.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Cc:     Vaibhav Jain <vaibhav@...ux.ibm.com>,
        Jonathan Corbet <corbet@....net>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Steven Rostedt (Google)" <rostedt@...dmis.org>,
        Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Subject: Re: [PATCH] powerpc: Enable generic cpu idle-loop

Vaibhav Jain <vaibhav@...ux.ibm.com> writes:
> This minor patch enables config option GENERIC_IDLE_POLL_SETUP for arch
> powerpc. This should add support for kernel param 'nohlt'.

Which is named after an 8086 instruction :), but oh well.

> Powerpc kernel also supports another kernel boot-time param called
> 'powersave' which can also be used to disable all cpu idle-states and
> forces CPU to an idle-loop similar to what cpu_idle_poll() does. This
> patch however makes powerpc kernel-parameters better aligned to the
> generic boot-time parameters.

It would be nice if we could make our powersave=off parameter just
enable this generic logic.

Have you looked at if that's possible? At a glance it looks like it
should be, when cpu_idle_force_poll is true do_idle() never calls
cpuidle_idle_call(), so the cpuidle drivers are never invoked.

cheers