From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965204AbdGTMWy (ORCPT ); Thu, 20 Jul 2017 08:22:54 -0400 Received: from merlin.infradead.org ([205.233.59.134]:51590 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935173AbdGTMWu (ORCPT ); Thu, 20 Jul 2017 08:22:50 -0400 Date: Thu, 20 Jul 2017 14:22:39 +0200 From: Peter Zijlstra To: Saravana Kannan Cc: Viresh Kumar , Rafael Wysocki , Ingo Molnar , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, smuckle.linux@gmail.com, eas-dev@lists.linaro.org Subject: Re: [Eas-dev] [PATCH V3 2/3] cpufreq: schedutil: Process remote callback for shared policies Message-ID: <20170720122239.licc6yjd7jwipcvk@hirez.programming.kicks-ass.net> References: <3fbaa9aaba19bfff5ff25d2c4141e88fb83f1ea9.1499927699.git.viresh.kumar@linaro.org> <5968263D.1020801@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5968263D.1020801@codeaurora.org> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 13, 2017 at 07:02:37PM -0700, Saravana Kannan wrote: > In all Qualcomm chipsets (well, at least the ones that have been used in > Android devices so far), we can switch the frequency of any CPU from any > other CPU. If we can do that even without fast switching, why wouldn't any > theoretical fast switching be incapable of supporting this? Is this a > limitation specific to x86 that we are assuming all architectures and > platforms are going to have? So the typical implementation of fast switching we're thinking of is the CPU writing the DVFS request into a machine register. Now machine registers are typically per logical CPU. What style of fast switching were you thinking of?