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From: Ulf Hansson <ulf.hansson@linaro.org>
To: Maulik Shah <quic_mkshah@quicinc.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	bjorn.andersson@linaro.org, linux-arm-msm@vger.kernel.org,
	linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
	quic_lsrao@quicinc.com, rnayak@codeaurora.org,
	Ingo Molnar <mingo@redhat.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>
Subject: Re: [PATCH] sched/idle: Export cpu_idle_poll_ctrl() symbol
Date: Fri, 26 Nov 2021 13:05:12 +0100	[thread overview]
Message-ID: <CAPDyKFo8Z+G-14t-o-HiHf1_xuexBAGo3eumca-0QO8eTqNpsw@mail.gmail.com> (raw)
In-Reply-To: <687d97b6-347a-92c0-34ba-00331dfb6c82@quicinc.com>

On Thu, 25 Nov 2021 at 15:13, Maulik Shah <quic_mkshah@quicinc.com> wrote:
>
> Hi Peter,
>
> On 11/25/2021 3:21 PM, Peter Zijlstra wrote:
> > On Thu, Nov 25, 2021 at 02:44:36PM +0530, Maulik Shah wrote:
> >> Export cpu_idle_poll_ctrl() so that module drivers can use same.
> > This does not seem like a really safe interface to expose to the
> > world.
>
> Thanks for the review.
>
> Keeping the cpuidle enabled from boot up may delay/increase the boot up
> time.
> Below is our use case to force cpuidle to stay in cpu_idle_poll().
>
> We keep cpuidle disabled from boot up using "nohlt" option of kernel
> command line which internally sets cpu_idle_force_poll = 1;
> and once the device bootup reaches till certain point (for example the
> android homescreen is up) userspace may notify a
> vendor module driver which can invoke cpu_idle_poll_ctrl(false); to come
> out of poll mode.
> So vendor module driver needs cpu_idle_poll_ctrl() exported symbol.

Waiting for the homescreen can be considered as rather late, from the
kernel boot progress point of view.

That said, I am wondering if a similar improvement can be achieved by
just allowing WFI (thus no deeper idle states) until homescreen? If
so, that can be quite easily achieved by modularizing the cpuidle-psci
driver.

[...]

Kind regards
Uffe

  parent reply	other threads:[~2021-11-26 12:41 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-25  9:14 Maulik Shah
2021-11-25  9:51 ` Peter Zijlstra
2021-11-25 14:13   ` Maulik Shah
2021-11-25 17:26     ` Daniel Lezcano
2021-11-26  5:56       ` Maulik Shah
2021-11-26 11:22         ` Daniel Lezcano
2021-11-26 12:05     ` Ulf Hansson [this message]
2021-11-25  9:18 Maulik Shah
2021-11-26  9:15 ` Christoph Hellwig

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