Re: [PATCH 0/4] CPUFreq statistics retrieved by drivers

From: Lukasz Luba
Date: Wed Aug 05 2020 - 15:24:41 EST

On 8/4/20 6:27 PM, Florian Fainelli wrote:

On 7/29/2020 8:12 AM, Lukasz Luba wrote:
Hi all,

The existing CPUFreq framework does not tracks the statistics when the
'fast switch' is used or when firmware changes the frequency independently
due to e.g. thermal reasons. However, the firmware might track the frequency
changes and expose this to the kernel.

Or the firmware might have changed the CPU frequency in response to a
request from the secure world for instance.


This patch set aims to introduce CPUfreq statistics gathered by firmware
and retrieved by CPUFreq driver. It would require a new API functions
in the CPUFreq, which allows to poke drivers to get these stats.

From a debugging perspective, it would be helpful if the firmware
maintained statistics were exposed as a super-set of the Linux cpufreq
statistics and aggregated into them such that you could view the normal
world vs. secure world residency of a given frequency point. This would
help because a lot of times, Linux requests freq X, but the secure world
requires freq Y (with X >= Y) and people do not really understand why
the resulting power usage is higher for instance.

What are your thoughts on this?

I know that Viresh is going to develop patches and improve these
cpufreq stats framework. Maybe he also had this 'aggregation' in mind.
I will leave it him.

Thank you for your feedback.