From: Vincent Guittot <vincent.guittot@linaro.org>
To: Juri Lelli <juri.lelli@arm.com>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
LAK <linux-arm-kernel@lists.infradead.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Russell King - ARM Linux <linux@arm.linux.org.uk>,
Sudeep Holla <sudeep.holla@arm.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Mark Brown <broonie@kernel.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Viresh Kumar <viresh.kumar@linaro.org>
Subject: Re: [PATCH v3 2/6] drivers/cpufreq: implement init_cpu_capacity_default()
Date: Thu, 4 Feb 2016 13:35:35 +0100 [thread overview]
Message-ID: <CAKfTPtDVasamRtG2kLxP0HsohmVQTPrXRgx36e+jb3gozDoo6g@mail.gmail.com> (raw)
In-Reply-To: <20160204121620.GB29586@e106622-lin>
On 4 February 2016 at 13:16, Juri Lelli <juri.lelli@arm.com> wrote:
> Hi Vincent,
>
> On 04/02/16 13:03, Vincent Guittot wrote:
>> On 4 February 2016 at 10:36, Morten Rasmussen <morten.rasmussen@arm.com> wrote:
>> > On Wed, Feb 03, 2016 at 10:04:37PM +0100, Vincent Guittot wrote:
>> >> On 3 February 2016 at 12:59, Juri Lelli <juri.lelli@arm.com> wrote:
>>
>> [snip]
>>
>> >> > diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
>> >> > index 9e63fb1..c4025fd 100644
>> >> > --- a/drivers/cpufreq/Makefile
>> >> > +++ b/drivers/cpufreq/Makefile
>> >> > @@ -1,5 +1,5 @@
>> >> > # CPUfreq core
>> >> > -obj-$(CONFIG_CPU_FREQ) += cpufreq.o freq_table.o
>> >> > +obj-$(CONFIG_CPU_FREQ) += cpufreq.o freq_table.o cpufreq_capacity.o
>> >>
>> >> Do you really want to have the calibration of capacity dependent of
>> >> cpufreq ? It means that we can't use it without a cpufreq driver.
>> >> IMHO, this creates a unnecessary dependency. I understand that you
>> >> must ensure that core runs at max fequency if a driver is present but
>> >> you should be able to calibrate the capacity if cpufreq is not
>> >> available but you have different capacity because micro architecture
>> >
>> > We could remove the dependency on cpufreq, but it would make things more
>> > complicated for systems which do have frequency scaling as we would have
>> > to either:
>> >
>> > 1) Run the calibration again once cpufreq has been initialized.
>>
>> or wait and let time for a driver to initialize and trig the
>> calibration. If calibration has not been done at the end of the boot,
>> you can force a calibration. If the cpufeq driver is a module and is
>> loaded far later for any good or bad reason, we will have to run the
>> calibration once again but at least the capacity will reflect he
>> current capacity of the CPUs.
>> I'm mainly worried that the compilation of the calibration is
>> dependent of CONFIG_CPU_FREQ not that cpufreq can trig the calibration
>> sequence
>>
>
> Yes, I guess we can make this work in some way. Out of curiosity,
> though, are out there heterogenous platforms that don't use cpufreq?
At least, you can find several heterogeneous platforms without OPP
table for CPUs in the kernel. That's probably a temporary situation
but which can become a permanent one. It means that we can't calibrate
the CPUs for these platforms.
Thanks,
Vincent
> I mean, I wouldn't add code and complexity from start, if there are not
> good reasons to do so.
>
> Thanks,
>
> - Juri
next prev parent reply other threads:[~2016-02-04 12:36 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-03 11:59 [PATCH v3 0/6] CPUs capacity information for heterogeneous systems Juri Lelli
2016-02-03 11:59 ` [PATCH v3 1/6] ARM: initialize cpu_scale to its default Juri Lelli
2016-02-03 11:59 ` [PATCH v3 2/6] drivers/cpufreq: implement init_cpu_capacity_default() Juri Lelli
2016-02-03 21:04 ` Vincent Guittot
2016-02-04 9:36 ` Morten Rasmussen
2016-02-04 12:03 ` Vincent Guittot
2016-02-04 12:16 ` Juri Lelli
2016-02-04 12:35 ` Vincent Guittot [this message]
2016-02-04 14:13 ` Juri Lelli
2016-02-04 15:44 ` Vincent Guittot
2016-02-04 15:46 ` Vincent Guittot
2016-02-05 9:30 ` Juri Lelli
2016-02-09 15:54 ` Dietmar Eggemann
2016-02-10 14:25 ` Juri Lelli
2016-02-03 11:59 ` [PATCH v3 3/6] arm: Enable dynamic CPU capacity initialization Juri Lelli
2016-02-03 11:59 ` [PATCH v3 4/6] arm64: " Juri Lelli
2016-02-08 12:28 ` Dietmar Eggemann
2016-02-08 13:13 ` Mark Brown
2016-02-08 13:41 ` Dietmar Eggemann
2016-02-03 11:59 ` [PATCH v3 5/6] arm: add sysfs cpu_capacity attribute Juri Lelli
2016-02-03 11:59 ` [PATCH v3 6/6] arm64: " Juri Lelli
2016-02-05 17:19 ` Dietmar Eggemann
2016-02-05 17:49 ` Juri Lelli
2016-02-08 23:59 ` [PATCH v3 0/6] CPUs capacity information for heterogeneous systems Steve Muckle
2016-02-09 10:37 ` Juri Lelli
2016-02-09 17:30 ` Steve Muckle
2016-02-09 17:40 ` Juri Lelli
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