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=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 E7B04C43331 for ; Wed, 1 Apr 2020 10:27:34 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 BED3320678 for ; Wed, 1 Apr 2020 10:27:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="AROsPPBP"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="r+TOVKl9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BED3320678 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=7zMwmKXaHsujnzq8so17cuhTYDudn6wVBCwHhYeH/Kc=; b=AROsPPBPVxB+pB aVhz6fR0WKs7FI79pQRKEdjFP5iNgQGa8caWyEBcfvvNMn3G8JmA6IQFRVUlXLjxSzSq9BCo7B9v+ 4Oi+xi5b/fbkySUZXYWaeTqAbzwDwegZdCLM+cMLBJw2Mm4qmxZLGrjyL29jsRCAAHLb6C4XhQiB3 v36pZDVzyAb6usrK1/5+gZ8TWiWTrrMDBIWcpowvuZWQ1m5ZhdCaFIWczq543gnBmdNGR37qwE4RQ A2nCt4MwyYcwGfAR/0zet4Tn15W0ZWoNHVSTv5YXV7dxHFS43coOHb6J+U7di/5DBIELtVHXnIPWc ffcSRl8ww6dwDLmQqU+w==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jJaar-0003lN-HH; Wed, 01 Apr 2020 10:27:33 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jJaao-0003kp-Ry for linux-arm-kernel@lists.infradead.org; Wed, 01 Apr 2020 10:27:32 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id F399B20678; Wed, 1 Apr 2020 10:27:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585736849; bh=2JbpQMYiOXz7o58BmgsmbK/PBMoQVEtIgYUut96G3zQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=r+TOVKl9nNY1i0+jDTKT2vJTE13dQlepQdsXp/Lp0VH7jYQ3tNeKrow33pcYd5B0d rHGcYwYNDkIsjH5KkDeUN5SL6SEc3XxOCnMWPs7qzioCtZ+1iFMrHFMb/VN6MKp92q q84jjpP5YdgQQXvwBIBW62ujDnur/yz7pBSv8qKo= Date: Wed, 1 Apr 2020 11:27:25 +0100 From: Will Deacon To: Mark Rutland Subject: Re: [PATCH] driver/perf: Add PMU driver for the ARM DMC-620 memory controller. Message-ID: <20200401102724.GA17575@willie-the-truck> References: <1584491381-31492-1-git-send-email-tuanphan@os.amperecomputing.com> <20200319151646.GC4876@lakrids.cambridge.arm.com> <23AD5E45-15E3-4487-9B0D-0D9554DD9DE8@amperemail.onmicrosoft.com> <20200320105315.GA35932@C02TD0UTHF1T.local> <20200401095226.GA17163@C02TD0UTHF1T.local> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200401095226.GA17163@C02TD0UTHF1T.local> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200401_032730_950014_4A273DCF X-CRM114-Status: GOOD ( 21.36 ) 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: Tuan Phan , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Tuan Phan Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Apr 01, 2020 at 10:52:26AM +0100, Mark Rutland wrote: > On Tue, Mar 31, 2020 at 03:14:59PM -0700, Tuan Phan wrote: > > > On Mar 20, 2020, at 4:25 AM, Mark Rutland wrote: > > > On Thu, Mar 19, 2020 at 12:03:43PM -0700, Tuan Phan wrote: > > >>> On Mar 19, 2020, at 8:16 AM, Mark Rutland wrote: > > >>> On Tue, Mar 17, 2020 at 05:29:38PM -0700, Tuan Phan wrote: > > >>>> +static int arm_dmc620_pmu_dev_init(struct arm_dmc620_pmu *dmc620_pmu) > > >>>> +{ > > >>>> + struct platform_device *pdev = dmc620_pmu->pdev; > > >>>> + int ret; > > >>>> + > > >>>> + ret = devm_request_irq(&pdev->dev, dmc620_pmu->irq, > > >>>> + arm_dmc620_pmu_handle_irq, > > >>>> + IRQF_SHARED, > > >>>> + dev_name(&pdev->dev), dmc620_pmu); > > >>> > > >>> This should have IRQF_NOBALANCING | IRQF_NO_THREAD. I don't think we > > >>> should have IRQF_SHARED. > > >> => I agree on having IRQF_NOBALANCING and IRQF_NO_THREAD. But > > >> IRQF_SHARED is needed. In our platform all DMC620s share same IRQs and > > >> any cpus can access the pmu registers. > > > > > > Linux needs to ensure that the same instance is concistently accessed > > > from the same CPU, and needs to migrate the IRQ to handle that. Given we > > > do that on a per-instance basis, we cannot share the IRQ with another > > > instance. > > > > > > Please feed back to you HW designers that muxing IRQs like this causes > > > significant problems for software. > > > > I looked at the SMMUv3 PMU driver and it also uses IRQF_SHARED. SMMUv3 > > PMU and DMC620 PMU are very much similar in which counters can be > > accessed by any cores using memory map. Any special reasons > > IRQF_SHARED works with SMMUv3 PMU driver? > > No; I believe that is a bug in the SMMUv3 PMU driver. If the IRQ were > shared, and another driver that held the IRQ changed the affinity, > things would go very wrong. I *think* the idea is that the SMMUv3 PMU driver manages multiple PMCG devices, which may all share an irq line, rather than the irq line being shared by some other driver that might change the affinity. So I suspect dropping IRQF_SHARED will break things. > Note that it's also missing IRQF_NOBALANCING, which is also necessary to > avoid such issues. unsigned long flags = IRQF_NOBALANCING | IRQF_SHARED | IRQF_NO_THREAD; so it looks like IRQF_NOBALANCING is already taken care of. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel