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=-5.5 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 BB6C3C433E3 for ; Fri, 17 Jul 2020 11:53:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9BBB72070E for ; Fri, 17 Jul 2020 11:53:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726079AbgGQLxN (ORCPT ); Fri, 17 Jul 2020 07:53:13 -0400 Received: from foss.arm.com ([217.140.110.172]:34456 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726040AbgGQLxM (ORCPT ); Fri, 17 Jul 2020 07:53:12 -0400 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 E4BFC30E; Fri, 17 Jul 2020 04:53:11 -0700 (PDT) Received: from [10.37.12.35] (unknown [10.37.12.35]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B78F53F66E; Fri, 17 Jul 2020 04:53:08 -0700 (PDT) Subject: Re: [PATCH v2 2/2] memory: samsung: exynos5422-dmc: Add module param to control IRQ mode From: Lukasz Luba To: Bartlomiej Zolnierkiewicz Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, willy.mh.wolff.ml@gmail.com, k.konieczny@samsung.com, cw00.choi@samsung.com, krzk@kernel.org, chanwoo@kernel.org, myungjoo.ham@samsung.com, kyungmin.park@samsung.com, s.nawrocki@samsung.com, kgene@kernel.org References: <20200710191122.11029-1-lukasz.luba@arm.com> <20200710191122.11029-3-lukasz.luba@arm.com> <1a389137-cab5-124a-e198-8be3bc2ca841@samsung.com> <3154b8d2-1fa8-c69d-8a9d-05832e12fdd1@arm.com> Message-ID: Date: Fri, 17 Jul 2020 12:53:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <3154b8d2-1fa8-c69d-8a9d-05832e12fdd1@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 7/14/20 10:01 AM, Lukasz Luba wrote: > Hi Bartek, > > On 7/14/20 8:42 AM, Bartlomiej Zolnierkiewicz wrote: >> >> Hi, >> >> On 7/10/20 9:11 PM, Lukasz Luba wrote: >>> The driver can operate in two modes relaying on devfreq monitoring >>> mechanism which periodically checks the device status or it can use >>> interrupts when they are provided by loaded Device Tree. The newly >>> introduced module parameter can be used to choose between devfreq >>> monitoring and internal interrupts without modifying the Device Tree. >>> It also sets devfreq monitoring as default when the parameter is not set >>> (also the case for default when the driver is not built as a module). >> >> Could you please explain why should we leave the IRQ mode >> support in the dmc driver? > > I am still experimenting with the IRQ mode in DMC, but have limited time > for it and no TRM. > The IRQ mode in memory controller or bus controller has one major > advantage: is more interactive. In polling we have fixed period, i.e. > 100ms - that's a lot when we have a sudden, latency sensitive workload. > There might be no check of the device load for i.e. 99ms, but the tasks > with such workload started running. That's a long period of a few frames > which are likely to be junked. Should we adjust polling interval to i.e. > 10ms, I don't think so. There is no easy way to address all of the > scenarios. > >> >> What are the advantages over the polling mode? > > As described above: more reactive to sudden workload, which might be > latency sensitive and cause junk frames. > Drawback: not best in benchmarks which are randomly jumping > over the data set, causing low traffic on memory. > It could be mitigated as Sylwester described with not only one type > of interrupt, but another, which could 'observe' also other information > type in the counters and fire. > >> >> In what scenarios it should be used? > > System like Android with GUI, when there is this sudden workload > quite often. > > I think the interconnect could help here and would adjust the DMC > freq upfront. Although I don't know if interconnect on Exynos5422 is in > your scope in near future. Of course the interconnect will not cover > all scenarios either. > > >> >> [ If this is only for documentation purposes then it should be >>    removed as it would stay in (easily accessible) git history >>    anyway.. ] > > The current interrupt mode is definitely not perfect and switching > to devfreq monitoring mode has more sense. On the other hand, it > still has potential, until there is no interconnect for this SoC. > I will continue experimenting with irq mode, so I would like to > still have the code in the driver. > > Regards, > Lukasz > >> >> Best regards, >> -- >> Bartlomiej Zolnierkiewicz >> Samsung R&D Institute Poland >> Samsung Electronics >> Bartek, do you have some objections to the patches or you think they can be taken via devfreq-next? Cheers, Lukasz 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=-5.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,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 88A5DC433E1 for ; Fri, 17 Jul 2020 11:54:52 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4D0DD2070E for ; Fri, 17 Jul 2020 11:54:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org 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v2 2/2] memory: samsung: exynos5422-dmc: Add module param to control IRQ mode From: Lukasz Luba To: Bartlomiej Zolnierkiewicz References: <20200710191122.11029-1-lukasz.luba@arm.com> <20200710191122.11029-3-lukasz.luba@arm.com> <1a389137-cab5-124a-e198-8be3bc2ca841@samsung.com> <3154b8d2-1fa8-c69d-8a9d-05832e12fdd1@arm.com> Message-ID: Date: Fri, 17 Jul 2020 12:53:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <3154b8d2-1fa8-c69d-8a9d-05832e12fdd1@arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200717_075318_433594_AB0A7E75 X-CRM114-Status: GOOD ( 32.34 ) 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: linux-samsung-soc@vger.kernel.org, s.nawrocki@samsung.com, linux-pm@vger.kernel.org, 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