Re: [RFC PATCH 1/3] cpufreq: Add new attribute "base_frequency"

From: Srinivas pandruvada <srinivas.pandruvada@linux.intel.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: rafael.j.wysocki@intel.com, linux-pm@vger.kernel.org
Subject: Re: [RFC PATCH 1/3] cpufreq: Add new attribute "base_frequency"
Date: Mon, 7 Sep 2015 08:17:15 -0700	[thread overview]
Message-ID: <55EDAA7B.7020301@linux.intel.com> (raw)
In-Reply-To: <20150907060648.GE26760@linux>


On 09/06/2015 11:06 PM, Viresh Kumar wrote:
> On 04-09-15, 10:19, Srinivas Pandruvada wrote:
>> Currently scaling_available_frequencies displays list of available
>> frequencies which can be used to set max/min or current scaling
>> frequency. But because of configurable thermal design power implementation
>> in several Intel CPUs, this is not a guaranteed frequency or a P state,
>> which user can request. After a limit all frequencies (P states) may be
>> purely in opportunistic performance range. For example
>>
>>> cat scaling_available_frequencies
>> 2301000 2300000 2200000 2000000 1900000 1800000 1700000 1500000 1400000
>> 1300000 1100000 1000000 900000 800000 600000 500000
>>
>> Here traditionally it is assumed that only 2301000 is a turbo frequency,
>> anything else user can request. But that is not true. Based on the
>> config TDP level, this turbo (boost) start can be much below. For
>> example it can be 2300000 or any other value.
>>
>> This change adds an optional new attribute called "base_frequency",
>> which displays the max non-turbo frequency (base frequency). For example:
>>> cat base_frequency
>> 2200000
> This is something very much acpi-cpufreq driver's specific and I don't
> really see other platform needing it. So, I would rather add this only
> for acpi-cpufreq driver, if at all it is required.
>
I can only add to acpi cpufeq. Once configurable TDP becomes standard 
feature, I think others will follow.

Thanks,
Srinivas