From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexandre Courbot Subject: Re: [PATCH RFC] Revert "cpufreq: dt: Identify cpu-sharing for platforms without operating-points-v2" Date: Thu, 16 Jun 2016 15:57:06 +0900 Message-ID: <5db9eb89-1026-e710-755b-c7a0fa87819e@nvidia.com> References: <20160616053524.19921-1-acourbot@nvidia.com> <20160616063529.GA5726@vireshk-i7> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20160616063529.GA5726@vireshk-i7> Sender: linux-kernel-owner@vger.kernel.org To: Viresh Kumar , "Rafael J. Wysocki" , Thierry Reding Cc: linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, gnurou@gmail.com List-Id: linux-pm@vger.kernel.org On 06/16/2016 03:35 PM, Viresh Kumar wrote: > +Rafael > > On 16-06-16, 14:35, Alexandre Courbot wrote: >> This is not an actual request for revert, but rather for comments about >> the observed behavior since I am not really familiar with cpufreq. >> >> I am observing a serious performance regression on Jetson TK1 since 4.7-rc1: >> namely, moving windows under X would become unsufferably slow, and graphical >> performance under X in general is seriously degraded. After bisecting, I >> found the regression to be visible since commit 1530b9963eeb ("cpufreq: dt: >> Identify cpu-sharing for platforms without operating-points-v2") >> >> If I revert this commit, I noticed that the CPU frequency immediately jumps to >> a higher frequency once I start moving windows (resulting in a smooth and >> responsive action), whereas enabling this commit causes the CPU frequency to >> remain low (typically 204 Mhz) in that case, resulting in CPU-bound slowness. >> >> What happens is that with 1530b9963eeb applied, dev_pm_opp_get_sharing_cpus() >> returns zero causing the fallback variable to remain false, whereas without it >> opp_v1 is set to true. >> >> It is not clear to me whether this is a cpufreq issue or a Tegra issue, so I am >> posting this in the hope to get clarifications from either side. >> >> Thanks! > > Yeah, you just hit a corner case. Sorry about that :( > > Can you try a patch that I sent to you instead? Its subject is: > > [PATCH] PM / OPP: 'UNKNOWN' status of opp-table->shared Thanks, this seems to solve the issue. > Also I would like to know one more thing. You can hit this bug only if > some other piece of code for your platform is creating OPP table for > the CPUs. Which code is doing that ? Good question. I am still educating myself about OPP - adding Thierry in the meantime who may have an answer.