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From: Sibi Sankar <sibis@codeaurora.org>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: ansuelsmth@gmail.com, vincent.guittot@linaro.org,
	saravanak@google.com, 'Sudeep Holla' <sudeep.holla@arm.com>,
	"'Rafael J. Wysocki'" <rjw@rjwysocki.net>,
	'Rob Herring' <robh+dt@kernel.org>,
	linux-pm@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: R: [RFC PATCH v3 0/2] Add Krait Cache Scaling support
Date: Thu, 03 Sep 2020 12:43:27 +0530
Message-ID: <6dc62d231c776b2cdfdc36cfe36e4140@codeaurora.org> (raw)
In-Reply-To: <20200903065314.y3ynhwydahaeg6o6@vireshk-i7>

On 2020-09-03 12:23, Viresh Kumar wrote:
> On 31-08-20, 09:41, ansuelsmth@gmail.com wrote:
>> On 31-08-20, Sibi wrote:
>> > On 2020-08-24 16:10, Viresh Kumar wrote:
>> > > +Vincent/Saravana/Sibi
>> > >
>> > > On 21-08-20, 16:00, Ansuel Smith wrote:
>> > >> This adds Krait Cache scaling support using the cpufreq notifier.
>> > >> I have some doubt about where this should be actually placed (clk or
>> > >> cpufreq)?
>> > >> Also the original idea was to create a dedicated cpufreq driver (like
>> > >> it's done in
>> > >> the codeaurora qcom repo) by copying the cpufreq-dt driver and adding
>> > >> the cache
>> > >> scaling logic but i still don't know what is better. Have a very
>> > >> similar driver or
>> > >> add a dedicated driver only for the cache using the cpufreq notifier
>> > >> and do the
>> > >> scale on every freq transition.
>> > >> Thanks to everyone who will review or answer these questions.
>> > >
>> > > Saravana was doing something with devfreq to solve such issues if I
>> > > wasn't mistaken.
>> > >
>> > > Sibi ?
>> >
>> > IIRC the final plan was to create a devfreq device
>> > and devfreq-cpufreq based governor to scale them, this
>> > way one can switch to a different governor if required.
>> 
>> So in this case I should convert this patch to a devfreq driver-
> 
> I think this should happen nevertheless. You are doing DVFS for a
> device which isn't a CPU and devfreq looks to be the right place of
> doing so.
> 
>> Isn't overkill to use a governor for such a task?
>> (3 range based on the cpufreq?)
> 
> I am not sure about the governor part here, maybe it won't be required
> ?

Yeah I don't see it being needed in ^^
case as well. I just mentioned them as
an advantage in case you wanted to switch
to a different governor in the future.

https://lore.kernel.org/lkml/d0bc8877-6d41-f54e-1c4c-2fadbb9dcd0b@samsung.com/

A devfreq governor tracking cpufreq was
generally accepted but using a cpufreq
notifier to achieve that was discouraged.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project.

  reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-21 14:00 Ansuel Smith
2020-08-21 14:00 ` [RFC PATCH v3 1/2] cpufreq: qcom: " Ansuel Smith
2020-08-21 14:00 ` [RFC PATCH v3 2/2] dt-bindings: cpufreq: Document Krait CPU Cache scaling Ansuel Smith
2020-08-24 17:28   ` Rob Herring
2020-08-24 10:40 ` [RFC PATCH v3 0/2] Add Krait Cache Scaling support Viresh Kumar
2020-08-31  5:45   ` Sibi Sankar
2020-08-31  7:41     ` R: " ansuelsmth
2020-09-03  6:53       ` Viresh Kumar
2020-09-03  7:13         ` Sibi Sankar [this message]
2020-09-03 11:00           ` R: " ansuelsmth

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