linux-kernel - Re: [PATCH v8 1/4] cpufreq: Introduce an optional cpuinfo_avg

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Message-ID: <Z2Haw_o8gF-Ce1gx@arm.com>
Date: Tue, 17 Dec 2024 21:10:43 +0100
From: Beata Michalska <beata.michalska@....com>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-pm@...r.kernel.org, ionela.voinescu@....com,
	sudeep.holla@....com, will@...nel.org, catalin.marinas@....com,
	rafael@...nel.org, sumitg@...dia.com, yang@...amperecomputing.com,
	vanshikonda@...amperecomputing.com, lihuisong@...wei.com,
	zhanjie9@...ilicon.com, Jonathan Corbet <corbet@....net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H . Peter Anvin" <hpa@...or.com>, Phil Auld <pauld@...hat.com>,
	x86@...nel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v8 1/4] cpufreq: Introduce an optional cpuinfo_avg_freq
 sysfs entry

On Tue, Dec 17, 2024 at 09:57:26AM +0530, Viresh Kumar wrote:
> On 16-12-24, 23:15, Beata Michalska wrote:
> > My bad as I must have misinterpreted that message. Although I am not entirely
> > sure why this might be unacceptable as it is not such uncommon approach to use
> > signed int space to cover both: expected positive value as well as potential
> > error code case failure.
> 
> This part is fine. The problem is with handling frequency here. Signed int can
> capture up to 2 GHz of freq, where as unsigned int can capture up to 4 GHz and
> so we would really like to keep it at 4 GHz..
Right, though the arch_freq_get_on_cpu operates on kHz values.

---
BR
Beata
> 
> Maybe we need to move to 64 bits for frequency at some point of time, but at
> least we should try to not break it for now.
> 
> > Enabling the new attribute for all is an option, tough not entirely compelling
> > one as exposing a feature that is known not to be supported seems bit
> > counterintuitive. On the other hand using cpufreq driver flags won't help much
> > as the support for the new attrib is platform-specific, not driver-specific.
> 
> -- 
> viresh