From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Shi Subject: Re: [PATCH] PM / QoS: Fix device resume latency PM QoS Date: Mon, 23 Oct 2017 13:12:43 +0800 Message-ID: <733a08d7-0dd6-36d6-fd3c-383bcfcbfd06@linaro.org> References: <2245486.jYtPfSLF5g@aspire.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pg0-f65.google.com ([74.125.83.65]:52704 "EHLO mail-pg0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750745AbdJWFMs (ORCPT ); Mon, 23 Oct 2017 01:12:48 -0400 Received: by mail-pg0-f65.google.com with SMTP id a192so10862681pge.9 for ; Sun, 22 Oct 2017 22:12:47 -0700 (PDT) In-Reply-To: <2245486.jYtPfSLF5g@aspire.rjw.lan> Content-Language: en-US Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "Rafael J. Wysocki" , Linux PM Cc: LKML , Reinette Chatre , Ramesh Thomas , Ulf Hansson On 10/20/2017 07:27 PM, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki > > The special value of 0 for device resume latency PM QoS means > "no restriction", but there are two problems with that. > > First, device resume latency PM QoS requests with 0 as the > value are always put in front of requests with positive > values in the priority lists used internally by the PM QoS > framework, causing 0 to be chosen as an effective constraint > value. However, that 0 is then interpreted as "no restriction" > effectively overriding the other requests with specific > restrictions which is incorrect. > > Second, the users of device resume latency PM QoS have no > way to specify that *any* resume latency at all should be > avoided, which is an artificial limitation in general. > > To address these issues, modify device resume latency PM QoS to > use S32_MAX as the "no constraint" value and 0 as the "no > latency at all" one and rework its users (the cpuidle menu > governor, the genpd QoS governor and the runtime PM framework) > to follow these changes. > > Also add a special "n/a" value to the corresponding user space I/F > to allow user space to indicate that it cannot accept any resume > latencies at all for the given device. > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=197323 > Signed-off-by: Rafael J. Wysocki > Reported-by: Reinette Chatre Acked-by: Alex Shi