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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Vaibhav Jain <vaibhav@linux.ibm.com>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Cc:     Vaibhav Jain <vaibhav@linux.ibm.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Nicholas Piggin <npiggin@gmail.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Peter Zijlstra <peterz@infradead.org>,
        "Steven Rostedt (Google)" <rostedt@goodmis.org>,
        Daniel Sneddon <daniel.sneddon@linux.intel.com>,
        Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Subject: Re: [PATCH] powerpc: Enable generic cpu idle-loop
In-Reply-To: <20230818050739.827851-1-vaibhav@linux.ibm.com>
References: <20230818050739.827851-1-vaibhav@linux.ibm.com>
Date:   Fri, 18 Aug 2023 21:18:24 +1000
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Vaibhav Jain <vaibhav@linux.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