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Thu, 18 Feb 2021 16:36:40 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1lCmIA-00026y-EU for linux-arm-kernel@lists.infradead.org; Thu, 18 Feb 2021 16:36:39 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 59FDA106F; Thu, 18 Feb 2021 08:36:37 -0800 (PST) Received: from localhost (unknown [10.1.195.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EF7E73F73D; Thu, 18 Feb 2021 08:36:36 -0800 (PST) Date: Thu, 18 Feb 2021 16:36:35 +0000 From: Ionela Voinescu To: Viresh Kumar Subject: Re: [PATCH V3 1/2] topology: Allow multiple entities to provide sched_freq_tick() callback Message-ID: <20210218163635.GA23622@arm.com> References: <20210203114521.GA6380@arm.com> <20210205091424.3od3tme3f7mh7ebp@vireshk-i7> <20210217002422.GA17422@arm.com> <20210218093304.3mt3o7kbeymn5ofl@vireshk-i7> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210218093304.3mt3o7kbeymn5ofl@vireshk-i7> User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210218_113638_580247_859AEF16 X-CRM114-Status: GOOD ( 23.03 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Vincent Guittot , linux-pm@vger.kernel.org, Catalin Marinas , Rafael Wysocki , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Sudeep Holla , Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hey, On Thursday 18 Feb 2021 at 15:03:04 (+0530), Viresh Kumar wrote: > On 17-02-21, 00:24, Ionela Voinescu wrote: > > > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c > > > index 1e47dfd465f8..47fca7376c93 100644 > > > --- a/arch/arm64/kernel/topology.c > > > +++ b/arch/arm64/kernel/topology.c > > > @@ -240,7 +240,6 @@ static struct scale_freq_data amu_sfd = { > > > > > > static void amu_fie_setup(const struct cpumask *cpus) > > > { > > > - bool invariant; > > > int cpu; > > > > > > /* We are already set since the last insmod of cpufreq driver */ > > > @@ -257,25 +256,10 @@ static void amu_fie_setup(const struct cpumask *cpus) > > > > > > cpumask_or(amu_fie_cpus, amu_fie_cpus, cpus); > > > > > > - invariant = topology_scale_freq_invariant(); > > > - > > > - /* We aren't fully invariant yet */ > > > - if (!invariant && !cpumask_equal(amu_fie_cpus, cpu_present_mask)) > > > - return; > > > - > > > > You still need these checks, otherwise you could end up with only part > > of the CPUs setting a scale factor, when only part of the CPUs support > > AMUs and there is no cpufreq support for FIE. > > Another look at it and here goes another reason (hope I don't have > another in-code comment somewhere else to kill this one) :) > > We don't need to care for the reason you gave (which is a valid reason > otherwise), as we are talking specifically about amu_fie_setup() here > and it gets called from cpufreq policy-notifier. i.e. we won't support > AMUs without cpufreq being there in the first place and the same goes > for cppc-driver. > > Does that sound reasonable ? > Yes, we don't care if there is no cpufreq driver, as the use of AMUs won't get initialised either. But we do care if there is a cpufreq driver that does not support frequency invariance, which is the example above. The intention with the patches that made cpufreq based invariance generic a while back was for it to be present, seamlessly, for as many drivers as possible, as a less than accurate invariance default method is still better than nothing. So only a few drivers today don't support cpufreq based FI, but it's not a guarantee that it will stay this way. Hope it makes sense, Ionela. > -- > viresh _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel