From mboxrd@z Thu Jan 1 00:00:00 1970 From: Viresh Kumar Subject: Re: [PATCH v8 6/6] cpufreq: powernv: Add sysfs attributes to show throttle stats Date: Wed, 3 Feb 2016 14:33:57 +0530 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 Return-path: Content-Disposition: inline In-Reply-To: <56B1BD71.2050403@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org 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 List-Id: linux-api@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