From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xdPjS6KVfzDqXw for ; Thu, 24 Aug 2017 23:07:56 +1000 (AEST) Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v7OD4etH061286 for ; Thu, 24 Aug 2017 09:07:54 -0400 Received: from e23smtp02.au.ibm.com (e23smtp02.au.ibm.com [202.81.31.144]) by mx0a-001b2d01.pphosted.com with ESMTP id 2chvsm8qsd-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 24 Aug 2017 09:07:53 -0400 Received: from localhost by e23smtp02.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 24 Aug 2017 23:07:51 +1000 Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by d23relay06.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v7OD7m0c38994008 for ; Thu, 24 Aug 2017 23:07:48 +1000 Received: from d23av03.au.ibm.com (localhost [127.0.0.1]) by d23av03.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id v7OD7e2W015173 for ; Thu, 24 Aug 2017 23:07:40 +1000 Date: Thu, 24 Aug 2017 18:37:42 +0530 From: Vaidyanathan Srinivasan To: Michael Ellerman Cc: linuxppc-dev@lists.ozlabs.org, Michael Neuling , Anton Blanchard Subject: Re: [PATCH] powerpc/powernv/idle: Round up latency and residency values Reply-To: svaidy@linux.vnet.ibm.com References: <20170823185841.25286-1-svaidy@linux.vnet.ibm.com> <877extw98c.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: <877extw98c.fsf@concordia.ellerman.id.au> Message-Id: <20170824130742.GA29369@drishya.in.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , * Michael Ellerman [2017-08-24 20:28:19]: > Vaidyanathan Srinivasan writes: > > > On PowerNV platforms, firmware provides exit latency and > > target residency for each of the idle states in nano > > seconds. Cpuidle framework expects the values in micro > > seconds. Round up to nearest micro seconds to avoid errors > > in cases where the values are defined as fractional micro > > seconds. > > > > Default idle state of 'snooze' has exit latency of zero. If > > other states have fractional micro second exit latency, they > > would get rounded down to zero micro second and make cpuidle > > framework choose deeper idle state when snooze loop is the > > right choice. > > > > Reported-by: Anton Blanchard > > Signed-off-by: Vaidyanathan Srinivasan > > This sounds like a fairly bad bug, does it need a Fixes / Cc stable tag? Yes, we will need this on stable kernel that runs on POWER9. On older platforms the latencies are larger and hence no impact :) I will post to stable after this fix hits your -next tree. --Vaidy