linux-kernel - Re: [PATCH V2] Revert "cpufreq: CPPC: Add support for frequency invariance"

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Date:   Fri, 11 Jun 2021 09:37:27 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Qian Cai <quic_qiancai@...cinc.com>,
        Sudeep Holla <sudeep.holla@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Ionela Voinescu <ionela.voinescu@....com>,
        linux-pm@...r.kernel.org, "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] Revert "cpufreq: CPPC: Add support for frequency
 invariance"

On Fri, Jun 11, 2021 at 08:48:02AM +0530, Viresh Kumar wrote:
> This reverts commit 4c38f2df71c8e33c0b64865992d693f5022eeaad.
> 
> There are few races in the frequency invariance support for CPPC driver,
> namely the driver doesn't stop the kthread_work and irq_work on policy
> exit during suspend/resume or CPU hotplug.
> 
> A proper fix won't be possible for the 5.13-rc, as it requires a lot of
> changes. Lets revert the patch instead for now.
> 
> Fixes: 4c38f2df71c8 ("cpufreq: CPPC: Add support for frequency invariance")
> Reported-by: Qian Cai <quic_qiancai@...cinc.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
> V2: Revert the original patch instead of marking it broken.
> 
>  drivers/cpufreq/Kconfig.arm    |  10 --
>  drivers/cpufreq/cppc_cpufreq.c | 245 ++-------------------------------
>  include/linux/arch_topology.h  |   1 -
>  kernel/sched/core.c            |   1 -
>  4 files changed, 12 insertions(+), 245 deletions(-)
> 
> diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> index a5c5f70acfc9..e65e0a43be64 100644
> --- a/drivers/cpufreq/Kconfig.arm
> +++ b/drivers/cpufreq/Kconfig.arm
> @@ -19,16 +19,6 @@ config ACPI_CPPC_CPUFREQ
>  
>  	  If in doubt, say N.
>  
> -config ACPI_CPPC_CPUFREQ_FIE
> -	bool "Frequency Invariance support for CPPC cpufreq driver"
> -	depends on ACPI_CPPC_CPUFREQ && GENERIC_ARCH_TOPOLOGY
> -	default y
> -	help
> -	  This extends frequency invariance support in the CPPC cpufreq driver,
> -	  by using CPPC delivered and reference performance counters.
> -
> -	  If in doubt, say N.
> -

Alternatively: "depends on BROKEN" ?