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Date:   Tue, 26 Mar 2019 12:38:17 +0100
From:   "Rafael J. Wysocki" <>
To:     Srinivas Pandruvada <>
Subject: Re: [PATCH v2 0/2] Correct the processing for base_frequency

On Monday, March 25, 2019 5:04:38 PM CET Srinivas Pandruvada wrote:
> The base_frequency display in cpufreq sysfs for intel_pstate gets the
> guaranteed ratio by reading CPPC guaranteed performance register as a
> first preference before falling back to x86 MSR for Hardware P-state
> Capabilities. The current code in cppc_acpi.c assumed that "guaranteed
> performance register" can be an integer field, which is invalid as per
> ACPI spec. So this change explicitly check for INTEGER values for
> invalid BIOS/firmware and ignore. 
> Also guaranteed performance register field is optional and when not
> present, nominal performance can be used as the guaranteed performance.
> But spec calls that this is true only in non-autonomous mode. So
> no change is made in cppc_acpi.c to make nominal as guaranteed in this
> case to avoid dependency on autonomous and non-autonomous mode. Instead
> a change is added to intel_pstate driver, which is specific to x86 to
> make nominal as guaranteed when guaranteed performance field is absent
> or has invalid value.
> Also we are working to clarify this non-autonomous mode requirement
> through ACPI standard body.
> v2:
> Changes done as suggested by Rafael.
> Srinivas Pandruvada (2):
>   ACPI / CPPC: Fix processing for guaranteed performance
>   cpufreq: intel_pstate: Also use cppc nominal_perf for base_frequency
>  drivers/acpi/cppc_acpi.c       | 9 +++++++--
>  drivers/cpufreq/intel_pstate.c | 5 ++++-
>  2 files changed, 11 insertions(+), 3 deletions(-)

Both applied, thanks!

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