From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A7A8C43215 for ; Mon, 18 Nov 2019 23:10:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F065A222A9 for ; Mon, 18 Nov 2019 23:10:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726905AbfKRXKJ (ORCPT ); Mon, 18 Nov 2019 18:10:09 -0500 Received: from cloudserver094114.home.pl ([79.96.170.134]:47618 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726922AbfKRXKF (ORCPT ); Mon, 18 Nov 2019 18:10:05 -0500 Received: from 79.184.253.244.ipv4.supernova.orange.pl (79.184.253.244) (HELO kreacher.localnet) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.292) id bde311d14881fd19; Tue, 19 Nov 2019 00:10:02 +0100 From: "Rafael J. Wysocki" To: Len Brown Cc: "Rafael J. Wysocki" , Linux PM , Peter Zijlstra , Daniel Lezcano , Doug Smythies , LKML Subject: [RFC][PATCH 0/2] cpuidle: Allow states to be disabled by default (was: Re: [PATCH] cpuidle: Consolidate disabled state checks) Date: Tue, 19 Nov 2019 00:04:59 +0100 Message-ID: <1688511.GgkECGP1XA@kreacher> In-Reply-To: References: <2717750.dCEzHT3DVQ@kreacher> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Monday, November 18, 2019 12:26:57 PM CET Rafael J. Wysocki wrote: > On Mon, Nov 18, 2019 at 10:22 AM Rafael J. Wysocki wrote: > > > > On Mon, Nov 18, 2019 at 5:46 AM Len Brown wrote: > > > > > > On Mon, Nov 4, 2019 at 6:16 AM Rafael J. Wysocki wrote: > > > > > > > > From: Rafael J. Wysocki > > > > > > > > There are two reasons why CPU idle states may be disabled: either > > > > because the driver has disabled them or because they have been > > > > disabled by user space via sysfs. > > > > > > > > In the former case, the state's "disabled" flag is set once during > > > > the initialization of the driver and it is never cleared later (it > > > > is read-only effectively). > > > > > > for x86 (intel_idle and acpi_idle), no states with disabled=1 are registered > > > with cpuidle. Instead, intel_idle (currently) skips them in the loop > > > that registers states. > > > (and acpi_idle never touches the disabled field) > > > > > > And so for x86, governors checking for drv->states[i].disabled is a NOP, > > > and the condition described by CPUIDLE_STATE_DISABLED_BY_DRIVER > > > does not (yet) exist. > > > > OK > > > > > Looking at the ARM code, it seems that cpuidle-imx6q.c and cpuidle-tegra20.c > > > reach into the cpuidle states at run time and toggle the > > > drv->states[i].disabled. > > > > I might have overlooked that, let me check. > > > > > It seems that this patch takes the initial value of > > > drv->states->disabled, and sets the (per cpu) > > > usage.disable=..BY_DRIVER, > > > but that subsequent run-time toggles in drv->states[i]disabled by > > > these drivers would be missed, > > > because you're removed the run-time checking of drv->states->disabled? > > > > If it is updated at run time, then yes, the updates will be missed, so > > thanks for pointing that out. > > > > > Finally, I'd like to change intel_idle so that it *can* register a > > > state that is disabled, by default. > > > If I change the driver to NOT skip registering disabled states, and > > > the cpuidle copy has cpuidle_state.disabled=1, > > > then the state is indeed, unused at run-time. But as you said, > > > it is effectively read-only, and is not indicated in sysfs, and can > > > not be changed via sysfs. > > > > > > One way to do this is to do what you do here and initialize > > > usage.disabled to drv->state.disabled. (not distinguishing between > > > DRIVER and USER) > > > That way the user could later over-ride what a driver set, by clearing > > > the disabled attribute. > > I'd rather get rid of the "disabled" field from struct cpuidle_state > entirely and introduce a new state flag to indicate the "disabled by > default" status. > > I also would expose that new flag in a new sysfs attribute of idle > states, say "disable_default". > > Then, the DISABLED_BY_DRIVER bit would be reserved for driver quirks > (as per https://patchwork.kernel.org/patch/11249519/) and the > DISABLED_BY_USER one could be used for all of the other purposes. To that end, I have the following two experimental patches (on top of https://patchwork.kernel.org/patch/11249519/) that IMO are simple enough. Please let me know what you think.