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From: <ansuelsmth@gmail.com>
To: "'Sibi Sankar'" <sibis@codeaurora.org>,
	"'Viresh Kumar'" <viresh.kumar@linaro.org>
Cc: <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: R: R: [RFC PATCH v3 0/2] Add Krait Cache Scaling support
Date: Thu, 3 Sep 2020 13:00:27 +0200
Message-ID: <01f201d681e1$70ff1bc0$52fd5340$@gmail.com> (raw)
In-Reply-To: <6dc62d231c776b2cdfdc36cfe36e4140@codeaurora.org>



> -----Messaggio originale-----
> Da: sibis=codeaurora.org@mg.codeaurora.org
> <sibis=codeaurora.org@mg.codeaurora.org> Per conto di Sibi Sankar
> Inviato: giovedì 3 settembre 2020 09:13
> A: 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
> Oggetto: Re: R: [RFC PATCH v3 0/2] Add Krait Cache Scaling support
> 
> 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.
> 

I read the patch discussion and it looks like at the very end they
lost interest in pushing it. That would very fit what I need here so
I'm asking how should I proceed? Keep the cpufreq notifier?
Introduce a dedicated governor? Ask them to resume the pushing or
try to include the changes to the passive governor by myself? 

> --
> 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
2020-09-03 11:00           ` ansuelsmth [this message]

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