linux-kernel - Re: [PATCH v3 2/2] cpufreq: add virtual-cpufreq driver

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Date:   Mon, 31 Jul 2023 15:02:47 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     David Dai <davidai@...gle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Saravana Kannan <saravanak@...gle.com>
Cc:     Quentin Perret <qperret@...gle.com>,
        Masami Hiramatsu <mhiramat@...gle.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Pavan Kondeti <quic_pkondeti@...cinc.com>,
        Gupta Pankaj <pankaj.gupta@....com>,
        Mel Gorman <mgorman@...e.de>, kernel-team@...roid.com,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] cpufreq: add virtual-cpufreq driver



On 7/31/23 10:46, David Dai wrote:
> diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
> index f429b9b37b76..3977ca796747 100644
> --- a/drivers/cpufreq/Kconfig
> +++ b/drivers/cpufreq/Kconfig
> @@ -217,6 +217,21 @@ config CPUFREQ_DT
>  
>  	  If in doubt, say N.
>  
> +config CPUFREQ_VIRT
> +        tristate "Virtual cpufreq driver"
> +	depends on OF
> +	select PM_OPP
> +        help

The 4 lines above should be indented with one tab (not 8 spaces).

> +	  This adds a virtualized cpufreq driver for guest kernels that
> +	  read/writes to a MMIO region for a virtualized cpufreq device to

	  reads/writes to an MMIO region

> +	  communicate with the host. It sends frequency updates to the host
> +	  which gets used as a hint to schedule vCPU threads and select CPU
> +	  frequency. If a VM does not support a virtualized FIE such as AMUs,
> +	  it updates the frequency scaling factor by polling host CPU frequency
> +	  to enable accurate Per-Entity Load Tracking for tasks running in the guest.
> +
> +	  If in doubt, say N.

-- 
~Randy