Date:   Thu, 19 May 2022 09:25:05 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     johnson.wang@...iatek.com, mka@...omium.org, wenst@...omium.org,
        jia-wei.chang@...iatek.com, andrew-sh.cheng@...iatek.com,
        hsinyi@...omium.org, saravanak@...gle.com,
        myungjoo.ham@...sung.com, kyungmin.park@...sung.com
Subject: Re: [PATCH v5 0/4] PM / devfreq: Add cpu based scaling support to
 passive governor

Hi Marek,

Thanks for the report.
It 


On 5/18/22 7:56 PM, Marek Szyprowski wrote:
> Hi,
> 
> On 17.05.2022 11:21, Chanwoo Choi 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.
> 
> I've just tested it on Exynos based boards and on all I see the 
> following issues after system suspend/resume cycle:
> 
> # time rtcwake -s10 -mmem
> rtcwake: wakeup from "mem" using /dev/rtc0 at Wed May 18 11:13:16 2022
> PM: suspend entry (deep)
> Filesystems sync: 0.001 seconds
> Freezing user space processes ... (elapsed 0.002 seconds) done.
> OOM killer disabled.
> Freezing remaining freezable tasks ... (elapsed 0.002 seconds) done.
> 
> ...
> 
> devfreq soc:bus-disp1-fimd: failed to suspend devfreq device
> devfreq soc:bus-jpeg-apb: failed to suspend devfreq device
> devfreq soc:bus-jpeg: failed to suspend devfreq device
> devfreq soc:bus-g2d-acp: failed to suspend devfreq device
> devfreq soc:bus-g2d: failed to suspend devfreq device
> devfreq soc:bus-peri: failed to suspend devfreq device
> devfreq soc:bus-gen: failed to suspend devfreq device
> devfreq soc:bus-mfc: failed to suspend devfreq device
> devfreq soc:bus-fsys2: failed to suspend devfreq device
> devfreq soc:bus-fsys-apb: failed to suspend devfreq device
> devfreq soc:bus-noc: failed to suspend devfreq device
> ...
> Disabling non-boot CPUs ...
> Enabling non-boot CPUs ...
> ...
> devfreq soc:bus-mscl: failed to resume devfreq device
> devfreq soc:bus-gscl-scaler: failed to resume devfreq device
> devfreq soc:bus-disp1: failed to resume devfreq device
> devfreq soc:bus-disp1-fimd: failed to resume devfreq device
> devfreq soc:bus-jpeg-apb: failed to resume devfreq device
> devfreq soc:bus-jpeg: failed to resume devfreq device
> devfreq soc:bus-g2d-acp: failed to resume devfreq device
> devfreq soc:bus-g2d: failed to resume devfreq device
> devfreq soc:bus-peri: failed to resume devfreq device
> devfreq soc:bus-gen: failed to resume devfreq device
> devfreq soc:bus-mfc: failed to resume devfreq device
> devfreq soc:bus-fsys2: failed to resume devfreq device
> devfreq soc:bus-fsys-apb: failed to resume devfreq device
> devfreq soc:bus-noc: failed to resume devfreq device
> 
> Some boards (like Trats2) after suspend/resume cycle reveals random crashes.
> 
> All those issues were not observed before applying this patchset.
> 
>> [1] [RFC,v2] PM / devfreq: Add cpu based scaling support to passive_governor
>> - https://lore.kernel.org/patchwork/patch/1101049/
>>
>> Changes from v4:
>> : https://patchwork.kernel.org/project/linux-pm/cover/20220511093554.17535-1-cw00.choi@samsung.com/
>> - Fix issue[2] reported by Marek Szyprowski
>> [2] https://patchwork.kernel.org/project/linux-pm/patch/20220511093554.17535-3-cw00.choi@samsung.com/
>>
>> Changes from v3:
>> : ttps://patchwork.kernel.org/project/linux-pm/cover/20220509120337.92472-1-cw00.choi@...sung.com/
>> - Add tested-by tag of both Chen-Yu Tsai and Johnson Wang
>> - Fix some typo
>>
>> 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
>>
>>   drivers/devfreq/devfreq.c          |  20 +-
>>   drivers/devfreq/governor.h         |  27 ++
>>   drivers/devfreq/governor_passive.c | 403 ++++++++++++++++++++++++-----
>>   include/linux/devfreq.h            |  17 +-
>>   4 files changed, 389 insertions(+), 78 deletions(-)
>>
> Best regards
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

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