Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752713AbeACMsB (ORCPT + 1 other); Wed, 3 Jan 2018 07:48:01 -0500 Received: from mail-vk0-f65.google.com ([209.85.213.65]:36024 "EHLO mail-vk0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751571AbeACMr7 (ORCPT ); Wed, 3 Jan 2018 07:47:59 -0500 X-Google-Smtp-Source: ACJfBovlX5axk2rzWXTJiHoCHF9Eatyvw+bABMpqInS5Dn+GUcNxoUyE2/bf8vdze+AnRTaOL9v3G8eMGr9G/FIlPBA= MIME-Version: 1.0 In-Reply-To: <3110289.BbUpyYVBQa@aspire.rjw.lan> References: <1513148261-21097-1-git-send-email-ego@linux.vnet.ibm.com> <20171218083820.GA28881@in.ibm.com> <3110289.BbUpyYVBQa@aspire.rjw.lan> From: Balbir Singh Date: Wed, 3 Jan 2018 23:47:58 +1100 Message-ID: Subject: Re: [v3 PATCH 2/3] powernv-cpufreq: Fix pstate_to_idx() to handle non-continguous pstates To: "Rafael J. Wysocki" Cc: Gautham R Shenoy , Shilpasri G Bhat , Viresh Kumar , Abhishek , Akshay Adiga , Michael Ellerman , Vaidyanathan Srinivasan , linux-pm@vger.kernel.org, "linux-kernel@vger.kernel.org" , "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Wed, Jan 3, 2018 at 11:07 PM, Rafael J. Wysocki wrote: > On Monday, December 18, 2017 9:38:20 AM CET Gautham R Shenoy wrote: >> Hi Balbir, >> >> On Sun, Dec 17, 2017 at 02:15:25PM +1100, Balbir Singh wrote: >> > On Wed, Dec 13, 2017 at 5:57 PM, Gautham R. Shenoy >> > wrote: >> > > From: "Gautham R. Shenoy" >> > > >> > > The code in powernv-cpufreq, makes the following two assumptions which >> > > are not guaranteed by the device-tree bindings: >> > > >> > > 1) Pstate ids are continguous: This is used in pstate_to_idx() to >> > > obtain the reverse map from a pstate to it's corresponding >> > > entry into the cpufreq frequency table. >> > > >> > > 2) Every Pstate should always lie between the max and the min >> > > pstates that are explicitly reported in the device tree: This >> > > is used to determine whether a pstate reported by the PMSR is >> > > out of bounds. >> > > >> > > Both these assumptions are unwarranted and can change on future >> > > platforms. >> > >> > While this is a good thing, I wonder if it is worth the complexity. Pstates >> > are contiguous because they define transitions in incremental value >> > of change in frequency and I can't see how this can be broken in the >> > future? >> >> In the future, we can have the OPAL firmware give us a smaller set of >> pstates instead of expose every one of them. As it stands today, for >> most of the workloads, we will need at best 20-30 pstates and not >> beyond that. > > I'm not sure about the status here. > > Is this good to go as is or is it going to be updated? > I have no major objections, except some of the added complexity, but Gautham makes a point that this is refactoring for the future Balbir Singh.