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From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Lukasz Luba <lukasz.luba@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-arm-msm@vger.kernel.org, sudeep.holla@arm.com,
	will@kernel.org, catalin.marinas@arm.com, linux@armlinux.org.uk,
	gregkh@linuxfoundation.org, rafael@kernel.org,
	viresh.kumar@linaro.org, amitk@kernel.org,
	daniel.lezcano@linaro.org, amit.kachhap@gmail.com,
	thara.gopinath@linaro.org, agross@kernel.org
Subject: Re: [PATCH v2 1/5] arch_topology: Introduce thermal pressure update function
Date: Thu, 28 Oct 2021 16:12:27 -0700	[thread overview]
Message-ID: <YXsuW+wOWoJzgMAA@ripper> (raw)
In-Reply-To: <a75b08d9-cf0f-b132-b07e-878b10d133a2@arm.com>

On Thu 28 Oct 00:16 PDT 2021, Lukasz Luba wrote:

> 
> 
> On 10/27/21 7:43 PM, Bjorn Andersson wrote:
> > On Fri 15 Oct 07:45 PDT 2021, Lukasz Luba wrote:
> > > diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h
> > [..]
> > > +/**
> > > + * topology_thermal_pressure_update() - Update thermal pressure for CPUs
> > > + * @cpus	: The related CPUs for which capacity has been reduced
> > > + * @capped_freq	: The maximum allowed frequency that CPUs can run at
> > 
> > I know this matches what I see in e.g. the Qualcomm cpufreq hw driver,
> > but in what cases will @capped_freq differ from
> > cpufreq_get_hw_max_freq(cpumask_first(cpus))?
> 
> The @capped_freq is the maximum allowed frequency value due to
> thermal reasons, which will always be lower or equal to the value
> returned by cpufreq_get_hw_max_freq()
> (effectively: 'policy->cpuinfo.max_freq').
> 

Read patch 3 and 4 again and now this makes sense to me.

Thanks,
Bjorn

> We limit the frequency (and voltage) of CPU to reduce power (and heat)
> in the passive cooling system. That information is important to us,
> because scheduler needs to know how fast the CPU can go. It cannot
> assume that the speed is always 'policy->cpuinfo.max_freq'. Often
> it's less then that at heavy load or GPU heavy load (the same SoC).
> 
> Regards,
> Lukasz

WARNING: multiple messages have this Message-ID (diff)
From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Lukasz Luba <lukasz.luba@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-arm-msm@vger.kernel.org, sudeep.holla@arm.com,
	will@kernel.org, catalin.marinas@arm.com, linux@armlinux.org.uk,
	gregkh@linuxfoundation.org, rafael@kernel.org,
	viresh.kumar@linaro.org, amitk@kernel.org,
	daniel.lezcano@linaro.org, amit.kachhap@gmail.com,
	thara.gopinath@linaro.org, agross@kernel.org
Subject: Re: [PATCH v2 1/5] arch_topology: Introduce thermal pressure update function
Date: Thu, 28 Oct 2021 16:12:27 -0700	[thread overview]
Message-ID: <YXsuW+wOWoJzgMAA@ripper> (raw)
In-Reply-To: <a75b08d9-cf0f-b132-b07e-878b10d133a2@arm.com>

On Thu 28 Oct 00:16 PDT 2021, Lukasz Luba wrote:

> 
> 
> On 10/27/21 7:43 PM, Bjorn Andersson wrote:
> > On Fri 15 Oct 07:45 PDT 2021, Lukasz Luba wrote:
> > > diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h
> > [..]
> > > +/**
> > > + * topology_thermal_pressure_update() - Update thermal pressure for CPUs
> > > + * @cpus	: The related CPUs for which capacity has been reduced
> > > + * @capped_freq	: The maximum allowed frequency that CPUs can run at
> > 
> > I know this matches what I see in e.g. the Qualcomm cpufreq hw driver,
> > but in what cases will @capped_freq differ from
> > cpufreq_get_hw_max_freq(cpumask_first(cpus))?
> 
> The @capped_freq is the maximum allowed frequency value due to
> thermal reasons, which will always be lower or equal to the value
> returned by cpufreq_get_hw_max_freq()
> (effectively: 'policy->cpuinfo.max_freq').
> 

Read patch 3 and 4 again and now this makes sense to me.

Thanks,
Bjorn

> We limit the frequency (and voltage) of CPU to reduce power (and heat)
> in the passive cooling system. That information is important to us,
> because scheduler needs to know how fast the CPU can go. It cannot
> assume that the speed is always 'policy->cpuinfo.max_freq'. Often
> it's less then that at heavy load or GPU heavy load (the same SoC).
> 
> Regards,
> Lukasz

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  reply	other threads:[~2021-10-28 23:10 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-15 14:45 [PATCH v2 0/5] Refactor thermal pressure update to avoid code duplication Lukasz Luba
2021-10-15 14:45 ` Lukasz Luba
2021-10-15 14:45 ` [PATCH v2 1/5] arch_topology: Introduce thermal pressure update function Lukasz Luba
2021-10-15 14:45   ` Lukasz Luba
2021-10-26 16:51   ` Dietmar Eggemann
2021-10-26 16:51     ` Dietmar Eggemann
2021-10-27  8:56     ` Lukasz Luba
2021-10-27  8:56       ` Lukasz Luba
2021-10-27 13:35       ` Dietmar Eggemann
2021-10-27 13:35         ` Dietmar Eggemann
2021-10-27 18:43   ` Bjorn Andersson
2021-10-27 18:43     ` Bjorn Andersson
2021-10-28  7:16     ` Lukasz Luba
2021-10-28  7:16       ` Lukasz Luba
2021-10-28 23:12       ` Bjorn Andersson [this message]
2021-10-28 23:12         ` Bjorn Andersson
2021-10-28  5:44   ` Viresh Kumar
2021-10-28  5:44     ` Viresh Kumar
2021-10-28  7:19     ` Lukasz Luba
2021-10-28  7:19       ` Lukasz Luba
2021-10-15 14:45 ` [PATCH v2 2/5] thermal: cpufreq_cooling: Use new " Lukasz Luba
2021-10-15 14:45   ` Lukasz Luba
2021-10-26 16:51   ` Dietmar Eggemann
2021-10-26 16:51     ` Dietmar Eggemann
2021-10-27  9:00     ` Lukasz Luba
2021-10-27  9:00       ` Lukasz Luba
2021-10-15 14:45 ` [PATCH v2 3/5] cpufreq: qcom-cpufreq-hw: Update offline CPUs per-cpu thermal pressure Lukasz Luba
2021-10-15 14:45   ` Lukasz Luba
2021-10-15 14:45 ` [PATCH v2 4/5] cpufreq: qcom-cpufreq-hw: Use new thermal pressure update function Lukasz Luba
2021-10-15 14:45   ` Lukasz Luba
2021-10-15 14:45 ` [PATCH v2 5/5] arch_topology: Remove unused topology_set_thermal_pressure() and related Lukasz Luba
2021-10-15 14:45   ` Lukasz Luba
2021-10-25 16:43 ` [PATCH v2 0/5] Refactor thermal pressure update to avoid code duplication Lukasz Luba
2021-10-25 16:43   ` Lukasz Luba

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