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Message-ID: <20160722003405.GZ27987@graphite.smuckle.net>
Date: Thu, 21 Jul 2016 17:34:05 -0700
From: Steve Muckle <steve.muckle@...aro.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Steve Muckle <steve.muckle@...aro.org>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Viresh Kumar <viresh.kumar@...aro.org>,
Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
Linux PM <linux-pm@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Morten Rasmussen <morten.rasmussen@....com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Juri Lelli <Juri.Lelli@....com>,
Patrick Bellasi <patrick.bellasi@....com>
Subject: Re: [PATCH V2] cpufreq: Disallow ->resolve_freq() for drivers
providing ->target_index()
On Fri, Jul 22, 2016 at 02:18:54AM +0200, Rafael J. Wysocki wrote:
> > My thinking was that one of these two would be preferable:
> >
> > - Forcing ->target() drivers to install a ->resolve_freq callback,
> > enforcing this at cpufreq driver init time.
>
> That would have been possible, but your series didn't do that.
>
> > My understanding is
> > ->target() drivers are deprecated anyway
>
> No, they aren't.
Ok. I didn't follow Documentation/cpu-freq/cpu-drivers.txt section 1.5
then - it suggests something about target() is deprecated, perhaps it's
out of date.
> There simply are cases in which frequency tables are not workable
> (like the ACPI CPPC one).
Sure that makes sense.
> > and theren't aren't many of
> > them, though I don't know offhand exactly how many or how hard it
> > would be to do for each one.
> >
> > - Forcing callers (schedutil in this case) to check that either
> > ->target() or ->resolve_freq() is implemented. It means
> > catching and scrutinizing future callers of resolve_freq.
>
> But that doesn't reduce the number of checks in cpufreq_driver_resolve_freq().
>
> There still are three choices in there: return a frequency from the
> table (if present), or call ->resolve_freq (if implemented), or return
> target_freq (as the last resort).
Sorry, that should've been "check that either ->target_index() or
->resolve_freq() is implemented."
Implementing resolve_freq for the target() drivers and requiring it at
driver init time is probably the better way to go though. Perhaps I can
work on this at some point.
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