From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934729AbdJJUZj (ORCPT ); Tue, 10 Oct 2017 16:25:39 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:50928 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932767AbdJJUZh (ORCPT ); Tue, 10 Oct 2017 16:25:37 -0400 From: Stewart Smith To: Michael Ellerman , Anju T Sudhakar Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, maddy@linux.vnet.ibm.com, hemant@linux.vnet.ibm.com, anju@linux.vnet.ibm.com Subject: Re: [PATCH] powerpc/powernv: Add kernel cmdline parameter to disable imc In-Reply-To: <87wp43wf2v.fsf@concordia.ellerman.id.au> References: <1507531597-25947-1-git-send-email-anju@linux.vnet.ibm.com> <87wp43wf2v.fsf@concordia.ellerman.id.au> Date: Wed, 11 Oct 2017 07:25:24 +1100 MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 x-cbid: 17101020-0040-0000-0000-000003B09420 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007874; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000235; SDB=6.00929258; UDB=6.00467698; IPR=6.00709529; BA=6.00005632; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00017480; XFM=3.00000015; UTC=2017-10-10 20:25:33 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17101020-0041-0000-0000-000007A59509 Message-Id: <87infmeonf.fsf@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-10-10_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=1 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1707230000 definitions=main-1710100291 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Michael Ellerman writes: > Anju T Sudhakar writes: > >> Add a kernel command line parameter option to disable In-Memory Collection >> (IMC) counters and add documentation. This helps in debug. > > I'd really rather we didn't. Do we *really* need this? > > We don't have command line parameters to disable any of the other ~20 > PMUs, why is this one special? You could also do the same thing by editing the device tree before booting your kernel, we do have the facility to do that in petitboot. A recent firmware patch: https://patchwork.ozlabs.org/patch/823249/ would fix the firmware implementation where the counters were already running before the INIT/START calls, which are likely the cause of the problems that this patch is trying to work around. I propose we have the firmware do the right thing and nothing special in kernel. i.e. not to merge this. -- Stewart Smith OPAL Architect, IBM.