linux-kernel - Re: [PATCH v2 0/8] PM / devfreq: Use OPP interface to handle the frequency

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Date:   Wed, 27 Sep 2017 10:28:07 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     myungjoo.ham@...sung.com, kyungmin.park@...sung.com
Cc:     rafael.j.wysocki@...el.com, chanwoo@...nel.org,
        inki.dae@...sung.com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/8] PM / devfreq: Use OPP interface to handle the
 frequency

Hi Myungjoo,

Could you please review this patchset?

On 2017년 09월 21일 09:33, Chanwoo Choi wrote:
> These patches makes the devfreq to use the OPP interface and clean-up codes.
> - patch 1~5 are related to the OPP interfaces. 
> - patch 6 removes the unneeded code.
> - patch 7 clean-up for the governor name.
> - patch 8 registers the cooling device for exynos-bus.
> 
> [Detaild Descripion]
> The commit a76caf55e5b3 ("thermal: Add devfreq cooling") provides
> the devfreq cooling device by using the OPP interface such as
> dev_pm_opp_disable() and dev_pm_opp_enable(). It means that
> the OPP interface is able to change the available status of the frequency.
> 
> Firstly, the existing devfreq doesn't use the OPP interface when showing
> the minimum and maximum frequency through the following sysfs nodes:
> It shows the wrong frequency value because min_freq/max_freq don't
> consider the frequency status by handling OPP interface
> (opp_dev_pm_opp_{disable|add}()). So, these patches fix this issue.
> - /sys/class/devfreq/devfreqX/min_freq
> - /sys/class/devfreq/devfreqX/max_freq
> 
> Second, the 'available_frequencies' should show the all supported frequencis
> even if the specific frequency is not available. It doesn't matter whether
> frequneyc is available or not. Because the role of 'available_frequencies'
> shows the all frequencies. Also, these patches fix this issue.
> - /sys/class/devfreq/devfreqX/available_frequencies
> 
> Third, update_devfreq() get the available next frequency by using
> the devfreq_recommended_opp() in order to consider the disabled OPP.
> 
> For example,
> - devfreq's min_freq is 100Mhz and max_freq is 700Mhz.
> - OPP disabled 500/600/700Mhz due to devfreq-cooling.c.
> - simple_ondemand govenor decided the next target_freq (600Mhz)
> |----------|-------------------------------------------------------------|
> |Freq(MHz) |100     |200    |300    |400     |500     |600      |70 0    |
> |Devfreq   |min_freq|       |       |        |        |         |max_freq|
> |OPP avail |enabled |enabled|enabled|enabled |Disabled| Disabled|Disabled|
> |Ondmenad  |        |       |       |        |        |next_freq|        |
> |------------------------------------------------------------------------|
> 
> In result,
> - Before this patch, target_freq is 600Mhz
>   and TRANSITION_NOTIFIER sends the next_freq is 600Mhz to the notifiee.
> - After this patch, target_freq is 400Mhz because 500/600 were disabled by OPP.
>   And TRANSITION_NOTIFIER sends the next_freq is 400Mhz to the notifiee.
> 
> Lastly,
> - patch6/7 fix the minor issue and cleanup codes.
> - patch8 register the cooling device. It depends on opp patch[1].
> [1] https://patchwork.kernel.org/patch/9962387/
> 
> Changes from v1:
> (https://lkml.org/lkml/2017/8/23/785)
> - Show the available frequencies as an ascending order
> - Change the author info from cwchoi00@...il.com to cw00.choi@...sung.com
> - Drop the patches related to opp_notifier
> - Add new patch5/6/7/8
> 
> Chanwoo Choi (8):
>   PM / devfreq: Set min/max_freq when adding the devfreq device
>   Revert "PM / devfreq: Add show_one macro to delete the duplicate code"
>   PM / devfreq: Show the available min/max frequency through sysfs node
>   PM / devfreq: Show the all available frequencies
>   PM / devfreq: Get the available next frequency on update_devfreq()
>   PM / devfreq: Remove unneeded conditional statement
>   PM / devfreq: Define the constant governor name
>   PM / devfreq: exynos-bus: Register cooling device
> 
>  drivers/devfreq/Kconfig                   |   1 +
>  drivers/devfreq/devfreq.c                 | 121 +++++++++++++++++++++++-------
>  drivers/devfreq/exynos-bus.c              |  16 +++-
>  drivers/devfreq/governor_passive.c        |   2 +-
>  drivers/devfreq/governor_performance.c    |   2 +-
>  drivers/devfreq/governor_powersave.c      |   2 +-
>  drivers/devfreq/governor_simpleondemand.c |   2 +-
>  drivers/devfreq/governor_userspace.c      |   2 +-
>  drivers/devfreq/rk3399_dmc.c              |   2 +-
>  include/linux/devfreq.h                   |   7 ++
>  10 files changed, 123 insertions(+), 34 deletions(-)
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics