From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH 8/8] sched: prefer cpufreq_scale_freq_capacity Date: Wed, 16 Mar 2016 21:07:52 +0100 Message-ID: <20160316200752.GJ6344@twins.programming.kicks-ass.net> References: <1457932932-28444-1-git-send-email-mturquette+renesas@baylibre.com> <1457932932-28444-9-git-send-email-mturquette+renesas@baylibre.com> <56E85EF6.5040005@arm.com> <20160315204630.30639.60702@quark.deferred.io> <56E9B7A1.5030806@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from casper.infradead.org ([85.118.1.10]:40700 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967008AbcCPUH4 (ORCPT ); Wed, 16 Mar 2016 16:07:56 -0400 Content-Disposition: inline In-Reply-To: <56E9B7A1.5030806@arm.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Dietmar Eggemann Cc: Michael Turquette , rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Juri.Lelli@arm.com, steve.muckle@linaro.org, morten.rasmussen@arm.com, vincent.guittot@linaro.org, Michael Turquette On Wed, Mar 16, 2016 at 07:44:33PM +0000, Dietmar Eggemann wrote: > intel_pstate (setpolicy()) is an exception but my humble guess is that > systems with intel_pstate driver have X86_FEATURE_APERFMPERF support. A quick browse of the Intel SDM says you're right. It looks like everything after Pentium-M; so Core-Solo/Core-Duo and onwards have APERF/MPERF. And it looks like P6 class systems didn't have DVFS support at all, which basically leaves P4 and Pentium-M as the only chips to have DVFS support lacking APERF/MPERF. And while I haven't got any P4 based space heaters left, I might still have a Pentium-M class laptop somewhere (if it still boots).