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

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Date:   Fri, 16 Jun 2023 12:55:39 +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 Wed, 14 Jun 2023 at 08:43, Tushar Nimkar <quic_tnimkar@...cinc.com> wrote:
>
> Thanks for response Ulf.
>
> On 6/12/2023 3:56 PM, Ulf Hansson wrote:
> > 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?
> >
> > [...]
> >
> This will not work for targets which does not have DLKM support.

Right. I am not saying it's the perfect solution, but it seems like it
could potentially solve the problem for many cases.

If you want some help to turn the cpuidle-psci driver into a loadable
module, just reach out, I am happy to help.

[...]

Kind regards
Uffe