linux-kernel - Re: [PATCH 3/4] PM / devfreq: Kconfig: add DEVFREQ_DELAYED

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Date:   Tue, 10 Dec 2019 10:39:15 +0100
From:   Kamil Konieczny <k.konieczny@...sung.com>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>
Subject: Re: [PATCH 3/4] PM / devfreq: Kconfig: add DEVFREQ_DELAYED_TIMER
 option

Hi,

On 09.12.2019 20:34, Matthias Kaehlcke wrote:
> On Mon, Dec 09, 2019 at 03:44:24PM +0100, Kamil Konieczny wrote:
>> Add Kconfig option DEVFREQ_DELAYED_TIMER. If set, devfreq workqueue
>> will use delayed timer from its start.
> 
> s/from its start/by default/
> 

thank you for review, I will correct this

>>
>> Signed-off-by: Kamil Konieczny <k.konieczny@...sung.com>
>> ---
>>  drivers/devfreq/Kconfig | 12 ++++++++++++
>>  1 file changed, 12 insertions(+)
>>
>> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
>> index 38a94df749a2..c799917c34c9 100644
>> --- a/drivers/devfreq/Kconfig
>> +++ b/drivers/devfreq/Kconfig
>> @@ -74,6 +74,18 @@ config DEVFREQ_GOV_PASSIVE
>>  	  through sysfs entries. The passive governor recommends that
>>  	  devfreq device uses the OPP table to get the frequency/voltage.
>>  
>> +comment "DEVFREQ Options"
>> +
>> +config DEVFREQ_DELAYED_TIMER
>> +	bool "Use delayed timer in Simple Ondemand Governor"
> 
> Is the use really limited to the Simple Ondemand Governor? I don't think
> so, at least the Tegra devfreq driver also does monitoring and others
> might follow.

There are currently:

simple_ondemand
performance
powersave
userspace
passive

>From them perfomance, powersave and userspace are fixed max, min or user provided,
so only left simple_ondemand and passive which could benefit from change.

>> +	default false
>> +	help
>> +	  Simple Ondemand Governor uses polling for reading buses counters.
>> +	  A default timer used is deferred, which saves power, but can
>> +	  miss increased demand for higher bus frequency if timer was
>> +	  assigned to idle cpu. If you want to change this to delayed
>> +	  timer at the cost of more power used, say Yes here.
>> +
>>  comment "DEVFREQ Drivers"
>>  
>>  config ARM_EXYNOS_BUS_DEVFREQ
> 
> 
> This patch on it's own does nothing. Squash it with '[4/4] PM / devfreq:
> use delayed work if DEVFREQ_DELAYED_TIMER set'.
> 
> 

-- 
Best regards,
Kamil Konieczny
Samsung R&D Institute Poland