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From: Ionela Voinescu <ionela.voinescu@arm.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: rjw@rjwysocki.net, catalin.marinas@arm.com, sudeep.holla@arm.com,
	will@kernel.org, linux@armlinux.org.uk,
	valentin.schneider@arm.com, mingo@redhat.com,
	peterz@infradead.org, dietmar.eggemann@arm.com,
	linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, Liviu Dudau <liviu.dudau@arm.com>
Subject: Re: [PATCH 4/8] cpufreq,vexpress-spc: fix Frequency Invariance (FI) for bL switching
Date: Thu, 2 Jul 2020 12:41:52 +0100	[thread overview]
Message-ID: <20200702114123.GA28120@arm.com> (raw)
In-Reply-To: <20200702030551.p4cevaahgfvpum4o@vireshk-i7>

Hi,

On Thursday 02 Jul 2020 at 08:35:51 (+0530), Viresh Kumar wrote:
> On 01-07-20, 15:07, Ionela Voinescu wrote:
> > On Wednesday 01 Jul 2020 at 16:16:19 (+0530), Viresh Kumar wrote:
> > > Is there anyone who cares for this driver and EAS ? I will just skip doing the
> > > FIE thing here and mark it skipped.
> > 
> > That is a good question. The vexpress driver is still used for TC2, but
> > I don't know of any users of this bL switcher functionality that's part
> > of the driver. I think there were a few people wondering recently if
> > it's still used [1].
> 
> Even if it is used by some, there is no need, I believe, to enable
> freq-invariance for it, which wasn't enabled until now.
>

It was enabled until now, but it was partially broken. If you look over
the driver you'll see arch_set_freq_scale() being called for both
is_bL_switching_enabled() and for when it's not [1].

For !is_bL_switching_enabled() this is fine. But for
is_bL_switching_enabled(), it is broken as described in 4/8.

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/cpufreq/vexpress-spc-cpufreq.c?h=v5.8-rc3#n203

> And considering that we are going to enable the flag only for the
> interested parties now, as from the discussion on 1/8, this shouldn't
> be required.
> 

If we just don't want frequency invariance for
is_bL_switching_enabled(), I can just guard the setting of the flag
suggested by Rafael at 1/8 by !CONFIG_BL_SWITCHER.

I'll proceed to do that and remove the fix at 4/8.

Many thanks!
Ionela.

> -- 
> viresh

WARNING: multiple messages have this Message-ID (diff)
From: Ionela Voinescu <ionela.voinescu@arm.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	peterz@infradead.org, catalin.marinas@arm.com, rjw@rjwysocki.net,
	linux@armlinux.org.uk, dietmar.eggemann@arm.com,
	mingo@redhat.com, sudeep.holla@arm.com,
	Liviu Dudau <liviu.dudau@arm.com>,
	will@kernel.org, valentin.schneider@arm.com,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 4/8] cpufreq,vexpress-spc: fix Frequency Invariance (FI) for bL switching
Date: Thu, 2 Jul 2020 12:41:52 +0100	[thread overview]
Message-ID: <20200702114123.GA28120@arm.com> (raw)
In-Reply-To: <20200702030551.p4cevaahgfvpum4o@vireshk-i7>

Hi,

On Thursday 02 Jul 2020 at 08:35:51 (+0530), Viresh Kumar wrote:
> On 01-07-20, 15:07, Ionela Voinescu wrote:
> > On Wednesday 01 Jul 2020 at 16:16:19 (+0530), Viresh Kumar wrote:
> > > Is there anyone who cares for this driver and EAS ? I will just skip doing the
> > > FIE thing here and mark it skipped.
> > 
> > That is a good question. The vexpress driver is still used for TC2, but
> > I don't know of any users of this bL switcher functionality that's part
> > of the driver. I think there were a few people wondering recently if
> > it's still used [1].
> 
> Even if it is used by some, there is no need, I believe, to enable
> freq-invariance for it, which wasn't enabled until now.
>

It was enabled until now, but it was partially broken. If you look over
the driver you'll see arch_set_freq_scale() being called for both
is_bL_switching_enabled() and for when it's not [1].

For !is_bL_switching_enabled() this is fine. But for
is_bL_switching_enabled(), it is broken as described in 4/8.

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/cpufreq/vexpress-spc-cpufreq.c?h=v5.8-rc3#n203

> And considering that we are going to enable the flag only for the
> interested parties now, as from the discussion on 1/8, this shouldn't
> be required.
> 

If we just don't want frequency invariance for
is_bL_switching_enabled(), I can just guard the setting of the flag
suggested by Rafael at 1/8 by !CONFIG_BL_SWITCHER.

I'll proceed to do that and remove the fix at 4/8.

Many thanks!
Ionela.

> -- 
> viresh

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  reply	other threads:[~2020-07-02 11:41 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-01  9:07 [PATCH 0/8] cpufreq: improve frequency invariance support Ionela Voinescu
2020-07-01  9:07 ` Ionela Voinescu
2020-07-01  9:07 ` [PATCH 1/8] cpufreq: allow drivers to flag custom support for freq invariance Ionela Voinescu
2020-07-01  9:07   ` Ionela Voinescu
2020-07-01 10:46   ` Viresh Kumar
2020-07-01 10:46     ` Viresh Kumar
2020-07-01 13:33     ` Ionela Voinescu
2020-07-01 13:33       ` Ionela Voinescu
2020-07-01 16:05       ` Rafael J. Wysocki
2020-07-01 16:05         ` Rafael J. Wysocki
2020-07-01 18:06         ` Ionela Voinescu
2020-07-01 18:06           ` Ionela Voinescu
2020-07-02  2:58         ` Viresh Kumar
2020-07-02  2:58           ` Viresh Kumar
2020-07-02 11:44           ` Ionela Voinescu
2020-07-02 11:44             ` Ionela Voinescu
2020-07-06 12:14             ` Dietmar Eggemann
2020-07-06 12:14               ` Dietmar Eggemann
2020-07-09  8:53               ` Ionela Voinescu
2020-07-09  8:53                 ` Ionela Voinescu
2020-07-09  9:09                 ` Viresh Kumar
2020-07-09  9:09                   ` Viresh Kumar
2020-07-01  9:07 ` [PATCH 2/8] cpufreq: move invariance setter calls in cpufreq core Ionela Voinescu
2020-07-01  9:07   ` Ionela Voinescu
2020-07-01 10:46   ` Viresh Kumar
2020-07-01 10:46     ` Viresh Kumar
2020-07-01 15:27     ` Ionela Voinescu
2020-07-01 15:27       ` Ionela Voinescu
2020-07-01 15:51       ` Rafael J. Wysocki
2020-07-01 15:51         ` Rafael J. Wysocki
2020-07-02  3:01         ` Viresh Kumar
2020-07-02  3:01           ` Viresh Kumar
2020-07-02 11:45         ` Ionela Voinescu
2020-07-02 11:45           ` Ionela Voinescu
2020-07-01  9:07 ` [PATCH 3/8] cpufreq,drivers: remove setting of frequency scale factor Ionela Voinescu
2020-07-01  9:07   ` [PATCH 3/8] cpufreq, drivers: " Ionela Voinescu
2020-07-01  9:07 ` [PATCH 4/8] cpufreq,vexpress-spc: fix Frequency Invariance (FI) for bL switching Ionela Voinescu
2020-07-01  9:07   ` [PATCH 4/8] cpufreq, vexpress-spc: " Ionela Voinescu
2020-07-01 10:46   ` [PATCH 4/8] cpufreq,vexpress-spc: " Viresh Kumar
2020-07-01 10:46     ` Viresh Kumar
2020-07-01 14:07     ` Ionela Voinescu
2020-07-01 14:07       ` Ionela Voinescu
2020-07-02  3:05       ` Viresh Kumar
2020-07-02  3:05         ` Viresh Kumar
2020-07-02 11:41         ` Ionela Voinescu [this message]
2020-07-02 11:41           ` Ionela Voinescu
2020-07-02 11:46           ` Viresh Kumar
2020-07-02 11:46             ` Viresh Kumar
2020-07-01  9:07 ` [PATCH 5/8] cpufreq: report whether cpufreq supports Frequency Invariance (FI) Ionela Voinescu
2020-07-01  9:07   ` Ionela Voinescu
2020-07-01 10:46   ` Viresh Kumar
2020-07-01 10:46     ` Viresh Kumar
2020-07-01  9:07 ` [PATCH 6/8] arch_topology,cpufreq,sched/core: constify arch_* cpumasks Ionela Voinescu
2020-07-01  9:07   ` [PATCH 6/8] arch_topology, cpufreq, sched/core: " Ionela Voinescu
2020-07-01  9:07 ` [PATCH 7/8] arch_topology,arm64: define arch_scale_freq_invariant() Ionela Voinescu
2020-07-01  9:07   ` Ionela Voinescu
2020-07-01 16:06   ` [PATCH 7/8] arch_topology, arm64: " kernel test robot
2020-07-01  9:07 ` [PATCH 8/8] cpufreq: make schedutil the default for arm and arm64 Ionela Voinescu
2020-07-01  9:07   ` Ionela Voinescu

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