From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933259AbcBCJEI (ORCPT ); Wed, 3 Feb 2016 04:04:08 -0500 Received: from mail-pf0-f182.google.com ([209.85.192.182]:34944 "EHLO mail-pf0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932490AbcBCJEB (ORCPT ); Wed, 3 Feb 2016 04:04:01 -0500 Date: Wed, 3 Feb 2016 14:33:57 +0530 From: Viresh Kumar To: Shilpasri G Bhat Cc: linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org, rjw@rjwysocki.net, linux-pm@vger.kernel.org, pc@us.ibm.com, anton@samba.org, ego@linux.vnet.ibm.com, shreyas@linux.vnet.ibm.com, bsingharora@gmail.com, mpe@ellerman.id.au, linux-api@vger.kernel.org Subject: Re: [PATCH v8 6/6] cpufreq: powernv: Add sysfs attributes to show throttle stats Message-ID: <20160203090357.GA31828@vireshk> References: <1454442102-1229-1-git-send-email-shilpa.bhat@linux.vnet.ibm.com> <1454442102-1229-7-git-send-email-shilpa.bhat@linux.vnet.ibm.com> <20160203082700.GZ31828@vireshk> <56B1BD71.2050403@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56B1BD71.2050403@linux.vnet.ibm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03-02-16, 14:12, Shilpasri G Bhat wrote: > I need the chip-id in the _show(). With just sysfs_create_group() I will > get the cpufreq_global_kobject in the _show() and I will not be able to > figure out the chip-id. The more I look at it, the more I am convinced that keeping this 'chip' directory in /sys/devices/system/cpu/cpuX/cpufreq/ makes sense. So, here is the deal: - A 'chip' on your platforms can contain multiple group of CPUs, which are represented by policies in cpufreq core. i.e. A chip can have multiple policies. - All CPUs present on the same chip are subject to same throttling outcomes. - Right now you are putting the 'chip' directory in cpu/cpufreq/ directory. Because that directory isn't specific to a policy, but entire cpufreq subsystem, you can't get a policy->cpu in the code for the kobject in question. And so you are *forced* to create a kobject, so that you can do container_of() and get chip->id. - And then you also need to unnecessarily add another field in the chip directory 'chip_mask', that is nothing but an bitwise OR operation on policy->related_cpus, so that userspace can know which policies/CPUs are managed by the 'chip'. What I can suggest is: - Move this directory inside cpuX/cpufreq/ directory, in a similar way as to how we create 'stats' directory today. - You can then get policy->cpu, to get chip->id out of it. - The only disadvantage here is that the same chip directory will be replicated in multiple policies, but that makes it more readable. Thoughts ? -- viresh