From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 03DE4C433FE for ; Tue, 8 Dec 2020 13:16:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D0BE523AA7 for ; Tue, 8 Dec 2020 13:16:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727258AbgLHNQD (ORCPT ); Tue, 8 Dec 2020 08:16:03 -0500 Received: from foss.arm.com ([217.140.110.172]:48696 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727135AbgLHNQD (ORCPT ); Tue, 8 Dec 2020 08:16:03 -0500 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 7181B30E; Tue, 8 Dec 2020 05:15:17 -0800 (PST) Received: from [10.57.61.26] (unknown [10.57.61.26]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 295BB3F718; Tue, 8 Dec 2020 05:15:15 -0800 (PST) Subject: Re: [PATCH v4 3/4] scmi-cpufreq: get opp_shared_cpus from opp-v2 for EM To: Sudeep Holla , Lukasz Luba , Viresh Kumar Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org, devicetree@vger.kernel.org, rjw@rjwysocki.net, vireshk@kernel.org, robh+dt@kernel.org, sboyd@kernel.org, nm@ti.com, daniel.lezcano@linaro.org, morten.rasmussen@arm.com, chris.redpath@arm.com References: <20201202172356.10508-1-nicola.mazzucato@arm.com> <20201202172356.10508-4-nicola.mazzucato@arm.com> <20201208055053.kggxw26kxtnpneua@vireshk-i7> <0e4d3134-f9b2-31fa-b454-fb30265a80b5@arm.com> <20201208072611.ptsqupv4y2wybs6p@vireshk-i7> <20201208112008.niesjrunxq2jz3kt@bogus> <1f9daaf8-e850-7c1b-7a32-71367982beaf@arm.com> <20201208122222.bp3o6y3xsxo642wd@bogus> From: Nicola Mazzucato Message-ID: <508c46a8-bf5a-bf29-a1df-c9a96b3de5f6@arm.com> Date: Tue, 8 Dec 2020 13:17:19 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20201208122222.bp3o6y3xsxo642wd@bogus> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi All, thanks for your feedback, please see below On 12/8/20 12:22 PM, Sudeep Holla wrote: > On Tue, Dec 08, 2020 at 11:34:36AM +0000, Lukasz Luba wrote: >> >> >> On 12/8/20 11:20 AM, Sudeep Holla wrote: >>> On Tue, Dec 08, 2020 at 12:56:11PM +0530, Viresh Kumar wrote: >>>> On 08-12-20, 07:22, Nicola Mazzucato wrote: >>>>> On 12/8/20 5:50 AM, Viresh Kumar wrote: >>>>>> On 02-12-20, 17:23, Nicola Mazzucato wrote: >>>>>>> nr_opp = dev_pm_opp_get_opp_count(cpu_dev); >>>>>>> if (nr_opp <= 0) { >>>>>>> - dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n"); >>>>>>> - ret = -EPROBE_DEFER; >>>>>>> - goto out_free_opp; >>>>>>> + ret = handle->perf_ops->device_opps_add(handle, cpu_dev); >>>>>>> + if (ret) { >>>>>>> + dev_warn(cpu_dev, "failed to add opps to the device\n"); >>>>>>> + goto out_free_cpumask; >>>>>>> + } >>>>>>> + >>>>>>> + ret = dev_pm_opp_set_sharing_cpus(cpu_dev, opp_shared_cpus); >>>>>>> + if (ret) { >>>>>>> + dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n", >>>>>>> + __func__, ret); >>>>>>> + goto out_free_cpumask; >>>>>>> + } >>>>>>> + >>>>>> >>>>>> Why do we need to call above two after calling >>>>>> dev_pm_opp_get_opp_count() ? >>>>> >>>>> Sorry, I am not sure to understand your question here. If there are no opps for >>>>> a device we want to add them to it >>>> >>>> Earlier we used to call handle->perf_ops->device_opps_add() and >>>> dev_pm_opp_set_sharing_cpus() before calling dev_pm_opp_get_opp_count(), why is >>>> the order changed now ? >>>> >>>> >>>> I am not sure why they would be duplicated in your case. I though >>>> device_opps_add() is responsible for dynamically adding the OPPs here. >>>> >>> >>> It is because of per-CPU vs per domain drama here. Imagine a system with >>> 4 CPUs which the firmware puts in individual domains while they all are >>> in the same perf domain and hence OPP is marked shared in DT. >>> >>> Since this probe gets called for all the cpus, we need to skip adding >>> OPPs for the last 3(add only for 1st one and mark others as shared). >>> If we attempt to add OPPs on second cpu probe, it *will* shout as duplicate >>> OPP as we would have already marked it as shared table with the first cpu. >>> Am I missing anything ? I suggested this as Nicola saw OPP duplicate >>> warnings when he was hacking up this patch. >>> >>>>> otherwise no need as they would be duplicated. >>>>>> And we don't check the return value of >>>>>> the below call anymore, moreover we have to call it twice now. >>> >>> Yes, that looks wrong, we need to add the check for non zero values, but .... will add the check, thanks >>> >>>>> >>>>> This second get_opp_count is required such that we register em with the correct >>>>> opp number after having added them. Without this the opp_count would not be correct. >>>> >>> >>> ... I have a question here. Why do you need to call >>> >>> em_dev_register_perf_domain(cpu_dev, nr_opp, &em_cb, opp_shared_cpus..) >>> >>> on each CPU ? Why can't that be done once for unique opp_shared_cpus ? I left it untouched to reduce changes, but I see your point. >> >> It just have to be called once, for one CPU from the mask. Otherwise for >> the next CPUs you should see error: >> "EM: exists for CPU%d" > > OK cool, at least it is designed and expected to be used like I thought. > Ah, I might have seen those, but never thought it was error message 😄 > >> It can happen that this print is not seen when the get_cpu_device(cpu) >> failed, but that would lead to investigation why CPU devices are not >> there yet. >> >> Nicola: have you seen that print? >> > > I assume you must see that and you need to pull this inside if condition > to do this once for each performance domain. I don't see that error, and that's also why I left it there. If there's already and em_pd for a device, EM just returns with an error that we don't check. I agree that it makes more sense to register em for opp_shared_cpus. > > -- > Regards, > Sudeep >