linux-kernel - Re: [PATCH 0/2] Add provision to keep idle state disabled

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Message-ID: <CAPDyKFqhVkMH42Vz0+a62j5kFh+R_CvGrcSU7hxoW__tjOhfLw@mail.gmail.com>
Date:   Mon, 12 Jun 2023 12:26:50 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Tushar Nimkar <quic_tnimkar@...cinc.com>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-pm@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, quic_lsrao@...cinc.com,
        quic_mkshah@...cinc.com
Subject: Re: [PATCH 0/2] Add provision to keep idle state disabled

On Thu, 8 Jun 2023 at 10:56, Tushar Nimkar <quic_tnimkar@...cinc.com> wrote:
>
> CPUidle already has CPUIDLE_FLAG_OFF to keep idle state disabled,
> Lets extend the support to set this flag using device tree.
>
> This allows to keep an idle state disabled and they can be enabled back using
> sysfs after certain point using below command.
>
> echo N > /sys/devices/system/cpu/cpuX/cpuidle/stateX/disable
>
> This helps in cases where vendors want to keep cpuidle off until home
> screen comes up. In the past attempt was done at [1] but it was not considered
> safe option to export cpu_idle_poll_ctrl().
>
> [1] https://patchwork.kernel.org/project/linux-arm-msm/patch/1637831676-32737-1-git-send-email-quic_mkshah@quicinc.com/

Before considering this, I don't recall if I ever received a reply to
my earlier suggestion to the above thread. So, let me repeat my
question.

I am wondering if a similar improvement can be achieved by
modularizing the cpuidle-psci driver. If insmodding it after the
homescreen, we allow only ARM WFI during boot. This should achieve the
similar results as we get with $subject series, right?

[...]

>
> Thanks,
> Tushar Nimkar.
>
> Tushar Nimkar (2):
>   dt-bindings: cpu: idle-states: Add idle-state-disabled property
>   cpuidle: dt: Add support to keep idle state disabled
>
>  Documentation/devicetree/bindings/cpu/idle-states.yaml | 8 ++++++++
>  drivers/cpuidle/dt_idle_states.c                       | 3 +++
>  2 files changed, 11 insertions(+)
>

Kind regards
Uffe