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

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Message-ID: <443b00b1-76b8-c31d-53d3-42e3592d26e8@quicinc.com>
Date:   Wed, 14 Jun 2023 12:13:19 +0530
From:   Tushar Nimkar <quic_tnimkar@...cinc.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
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

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.

>>
>> 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

Thanks,
Tushar