Re: R: [RFC PATCH v3 0/2] Add Krait Cache Scaling support

[Sibi Sankar]

On 2020-09-03 12:23, Viresh Kumar wrote:
> On 31-08-20, 09:41, ansuelsmth@xxxxxxxxx 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@xxxxxxxxxxx/

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

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