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

From: Ulf Hansson <ulf.hansson@linaro.org>
To: Tushar Nimkar <quic_tnimkar@quicinc.com>
Cc: "Rafael J . Wysocki" <rafael@kernel.org>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	linux-pm@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	linux-kernel@vger.kernel.org, quic_lsrao@quicinc.com,
	quic_mkshah@quicinc.com
Subject: Re: [PATCH 0/2] Add provision to keep idle state disabled
Date: Fri, 16 Jun 2023 12:55:39 +0200	[thread overview]
Message-ID: <CAPDyKFp5L454WmTPo2eYnBuZ=ZMKEtinLgYU09n=J=3DA1FSJQ@mail.gmail.com> (raw)
In-Reply-To: <443b00b1-76b8-c31d-53d3-42e3592d26e8@quicinc.com>

On Wed, 14 Jun 2023 at 08:43, Tushar Nimkar <quic_tnimkar@quicinc.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@quicinc.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