linux-kernel - Re: [PATCH v3 0/4] PM / devfreq: Add cpu based scaling support to passive governor

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Date:   Tue, 10 May 2022 17:00:37 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     Chanwoo Choi <cwchoi00@...il.com>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        johnson.wang@...iatek.com, mka@...omium.org,
        jia-wei.chang@...iatek.com, andrew-sh.cheng@...iatek.com,
        hsinyi@...omium.org, saravanak@...gle.com, cw00.choi@...sung.com,
        myungjoo.ham@...sung.com, kyungmin.park@...sung.com
Subject: Re: [PATCH v3 0/4] PM / devfreq: Add cpu based scaling support to
 passive governor

On Mon, May 9, 2022 at 8:03 PM Chanwoo Choi <cwchoi00@...il.com> wrote:
>
> The devfreq passive governor has already supported the devfreq parent device
> for coupling the frequency change if some hardware have the constraints
> such as power sharing and so on.
>
> Add cpu based scaling support to passive governor with required-opp property.
> It uses the cpufreq notifier to catch the frequency change timing of cpufreq
> and get the next frequency according to new cpu frequency by using required-opp
> property. It is based on patch[1] and then just code clean-up by myself.
>
> Make the common code for both passive_devfreq and passive_cpufreq
> parent type to remove the duplicate code.
>
> [1] [RFC,v2] PM / devfreq: Add cpu based scaling support to passive_governor
> - https://lore.kernel.org/patchwork/patch/1101049/
>
> Changes from v2:
> : https://patchwork.kernel.org/project/linux-pm/cover/20220507150145.531864-1-cw00.choi@samsung.com/
> - Drop the following patch ("PM / devfreq: passive: Update frequency when start governor")
> - Move p_data->this initialization into cpufreq_passive_regiser_notifier()
>
> Changes from v1:
> : https://patchwork.kernel.org/project/linux-pm/cover/20210617060546.26933-1-cw00.choi@samsung.com/
> - Rename cpu_data variable to parent_cpu_data to avoid build fail
> - Use for_each_possible_cpu macro when register cpufreq transition notifier
> - Add missing exception handling when cpufreq_passive_register_notifier is failed
> - Keep cpufreq_policy for posible cpus instead of NR_CPU in order to avoid
>   the memory waste when NR_CPU is too high.
> - Add reviewed-by tag of Matthias Kaehlcke for patch1
>
>
> Chanwoo Choi (3):
>   PM / devfreq: Export devfreq_get_freq_range symbol within devfreq
>   PM / devfreq: passive: Reduce duplicate code when passive_devfreq case
>   PM / devfreq: passive: Keep cpufreq_policy for possible cpus
>
> Saravana Kannan (1):
>   PM / devfreq: Add cpu based scaling support to passive governor

Tested-by: Chen-Yu Tsai <wenst@...omium.org>

on next-20220509 in conjunction with the MediaTek cpufreq [1], CCI devfreq [2]
& SVS [3] series, as well as some fix-ups [4]. AFAICT the CCI devfreq device
is reacting and making frequency changes.


Regards
ChenYu

[1] https://lore.kernel.org/all/20220422075239.16437-1-rex-bc.chen@mediatek.com/
[2] https://lore.kernel.org/all/20220408052150.22536-1-johnson.wang@mediatek.com/
[3] https://lore.kernel.org/all/20220420102044.10832-1-roger.lu@mediatek.com/
[4] https://github.com/wens/linux/commits/mt8183-cpufreq-cci-svs-test