From: Ionela Voinescu <ionela.voinescu@arm.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linux-pm@vger.kernel.org, peterz@infradead.org,
catalin.marinas@arm.com, rjw@rjwysocki.net,
linux@armlinux.org.uk, linux-kernel@vger.kernel.org,
mingo@redhat.com, sudeep.holla@arm.com, will@kernel.org,
dietmar.eggemann@arm.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 2/7] cpufreq: set invariance scale factor on transition end
Date: Mon, 3 Aug 2020 14:58:38 +0100 [thread overview]
Message-ID: <20200803135838.GB9512@arm.com> (raw)
In-Reply-To: <20200730041334.cjg5mc5xpopd2lst@vireshk-mac-ubuntu>
Hi Viresh,
On Thursday 30 Jul 2020 at 09:43:34 (+0530), Viresh Kumar wrote:
> On 22-07-20, 10:37, Ionela Voinescu wrote:
> > While the move of the invariance setter calls (arch_set_freq_scale())
> > from cpufreq drivers to cpufreq core maintained the previous
> > functionality for existing drivers that use target_index() and
> > fast_switch() for frequency switching, it also gives the possibility
> > of adding support for users of the target() callback, which is exploited
> > here.
> >
> > To be noted that the target() callback has been flagged as deprecated
> > since:
> >
> > commit 9c0ebcf78fde ("cpufreq: Implement light weight ->target_index() routine")
> >
> > It also doesn't have that many users:
> >
> > cpufreq-nforce2.c:371:2: .target = nforce2_target,
> > cppc_cpufreq.c:416:2: .target = cppc_cpufreq_set_target,
> > gx-suspmod.c:439:2: .target = cpufreq_gx_target,
> > pcc-cpufreq.c:573:2: .target = pcc_cpufreq_target,
> >
> > Similarly to the path taken for target_index() calls in the cpufreq core
> > during a frequency change, all of the drivers above will mark the end of a
> > frequency change by a call to cpufreq_freq_transition_end().
> >
> > Therefore, cpufreq_freq_transition_end() can be used as the location for
> > the arch_set_freq_scale() call to potentially inform the scheduler of the
> > frequency change.
> >
> > This change maintains the previous functionality for the drivers that
> > implement the target_index() callback, while also adding support for the
> > few drivers that implement the deprecated target() callback.
> >
> > Two notes are worthwhile here:
> > - In __target_index(), cpufreq_freq_transition_end() is called only for
> > drivers that have synchronous notifications enabled. There is only one
> > driver that disables them,
> >
> > drivers/cpufreq/powernow-k8.c:1142: .flags = CPUFREQ_ASYNC_NOTIFICATION,
> >
> > which is deprecated.
>
> I don't think this is deprecated.
Sorry, possibly 'deprecated' is a strong word.
As far as I knew acpi_cpufreq was recommended more recently for K8/K10
CPUs so that's why I decided not to create a special case for it, also
considering that it was not supporting cpufreq-based frequency
invariance to begin with.
We could support this as well by having a call to arch_set_freq_scale()
on the else path in __target_index(). But given that there was only this
one user of CPUFREQ_ASYNC_NOTIFICATION, I thought I'd propose this simpler
version first.
Let me know if my reasoning is wrong.
Thank you,
Ionela.
>
> --
> viresh
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next prev parent reply other threads:[~2020-08-03 14:00 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-22 9:37 [PATCH v2 0/7] cpufreq: improve frequency invariance support Ionela Voinescu
2020-07-22 9:37 ` [PATCH v2 1/7] cpufreq: move invariance setter calls in cpufreq core Ionela Voinescu
2020-07-27 13:48 ` Rafael J. Wysocki
2020-07-29 9:03 ` Ionela Voinescu
2020-07-30 3:41 ` Viresh Kumar
2020-08-03 13:26 ` Ionela Voinescu
2020-08-03 13:46 ` Rafael J. Wysocki
2020-08-03 14:16 ` Ionela Voinescu
2020-07-22 9:37 ` [PATCH v2 2/7] cpufreq: set invariance scale factor on transition end Ionela Voinescu
2020-07-27 13:52 ` Rafael J. Wysocki
2020-07-29 9:14 ` Ionela Voinescu
2020-07-30 4:13 ` Viresh Kumar
2020-08-03 13:58 ` Ionela Voinescu [this message]
2020-08-04 6:26 ` Viresh Kumar
2020-08-05 10:35 ` Ionela Voinescu
2020-07-22 9:37 ` [PATCH v2 3/7] arch_topology: disable frequency invariance for CONFIG_BL_SWITCHER Ionela Voinescu
2020-07-30 4:24 ` Viresh Kumar
2020-07-30 10:29 ` Dietmar Eggemann
2020-07-31 15:48 ` Sudeep Holla
2020-08-03 14:39 ` Ionela Voinescu
2020-08-04 6:30 ` Viresh Kumar
2020-08-10 9:01 ` Ionela Voinescu
2020-07-22 9:37 ` [PATCH v2 4/7] cpufreq: report whether cpufreq supports Frequency Invariance (FI) Ionela Voinescu
2020-07-27 14:02 ` Rafael J. Wysocki
2020-07-29 14:39 ` Ionela Voinescu
2020-07-30 4:43 ` Viresh Kumar
2020-08-03 15:24 ` Ionela Voinescu
2020-08-04 6:46 ` Viresh Kumar
2020-08-05 10:35 ` Ionela Voinescu
2020-07-22 9:37 ` [PATCH v2 5/7] arch_topology, cpufreq, sched/core: constify arch_* cpumasks Ionela Voinescu
2020-07-30 11:43 ` Catalin Marinas
2020-07-22 9:37 ` [PATCH v2 6/7] arch_topology, arm, arm64: define arch_scale_freq_invariant() Ionela Voinescu
2020-07-30 11:44 ` [PATCH v2 6/7] arch_topology,arm,arm64: " Catalin Marinas
2020-07-22 9:37 ` [PATCH v2 7/7] cpufreq: make schedutil the default for arm and arm64 Ionela Voinescu
2020-07-30 4:54 ` Viresh Kumar
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