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From: Viresh Kumar <viresh.kumar@linaro.org>
To: Ionela Voinescu <ionela.voinescu@arm.com>
Cc: catalin.marinas@arm.com, sudeep.holla@arm.com, will@kernel.org,
	linux@armlinux.org.uk, rjw@rjwysocki.net,
	dietmar.eggemann@arm.com, valentin.schneider@arm.com,
	linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] arm: disable frequency invariance for CONFIG_BL_SWITCHER
Date: Tue, 6 Oct 2020 12:40:34 +0530	[thread overview]
Message-ID: <20201006071034.u65c5sphzwlvi6cs@vireshk-i7> (raw)
In-Reply-To: <20200924123016.13427-3-ionela.voinescu@arm.com>

On 24-09-20, 13:30, Ionela Voinescu wrote:
> big.LITTLE switching complicates the setting of a correct cpufreq-based
> frequency invariance scale factor due to (as observed in
> drivers/cpufreq/vexpress-spc-cpufreq.c):
>  - Incorrect current and maximum frequencies as a result of the
>    exposure of a virtual frequency table to the cpufreq core,
>  - Missed updates as a result of asynchronous frequency adjustments
>    caused by frequency changes in other CPU pairs.
> 
> Given that its functionality is atypical in regards to frequency
> invariance and this is an old technology, disable frequency
> invariance for when big.LITTLE switching is configured in to prevent
> incorrect scale setting.
> 
> Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
> Suggested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> ---
>  arch/arm/include/asm/topology.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h
> index e5e3d5ce4d55..470299ee2fba 100644
> --- a/arch/arm/include/asm/topology.h
> +++ b/arch/arm/include/asm/topology.h
> @@ -7,10 +7,13 @@
>  #include <linux/cpumask.h>
>  #include <linux/arch_topology.h>
>  
> +/* big.LITTLE switcher is incompatible with frequency invariance */
> +#ifndef CONFIG_BL_SWITCHER
>  /* Replace task scheduler's default frequency-invariant accounting */
>  #define arch_set_freq_scale topology_set_freq_scale
>  #define arch_scale_freq_capacity topology_get_freq_scale
>  #define arch_scale_freq_invariant topology_scale_freq_invariant
> +#endif
>  
>  /* Replace task scheduler's default cpu-invariant accounting */
>  #define arch_scale_cpu_capacity topology_get_cpu_scale

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

-- 
viresh

  reply	other threads:[~2020-10-06  7:10 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-24 12:30 [PATCH 0/2]cpufreq,topology,arm: disable FI for BL_SWITCHER Ionela Voinescu
2020-09-24 12:30 ` [PATCH 1/2] cpufreq,arm,arm64: restructure definitions of arch_set_freq_scale() Ionela Voinescu
2020-10-06  7:05   ` Viresh Kumar
2020-10-06 17:09     ` Ionela Voinescu
2020-10-07  5:12   ` Viresh Kumar
2020-10-07 15:21   ` Catalin Marinas
2020-09-24 12:30 ` [PATCH 2/2] arm: disable frequency invariance for CONFIG_BL_SWITCHER Ionela Voinescu
2020-10-06  7:10   ` Viresh Kumar [this message]
2020-10-07 14:34 ` [PATCH 0/2]cpufreq,topology,arm: disable FI for BL_SWITCHER Rafael J. Wysocki
2020-10-08 14:05   ` Sudeep Holla
2020-10-08 15:18     ` Rafael J. Wysocki
2020-10-08 16:07       ` Ionela Voinescu

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