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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 7E950C2D0F1 for ; Wed, 1 Apr 2020 11:57:11 +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 4F8A920776 for ; Wed, 1 Apr 2020 11:57:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="QygUuWg1" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4F8A920776 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com 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-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Mj+HSH+xxRY5j7mN3E+oB1XbYUWDveoNxEvLKpEM4UM=; b=QygUuWg1Sp6NmT4u1yHNb4UEj TzgT9dKZBTYIEDM72LBmRjFQADloqnO5Ql8od3c2cymrkHNvmB/IE1Mvw6qxpNHJg4YnX/waVo0Wv 9kJ0LrskTAGBu/oV70tzfuV2M1nOHIyYg6oQ4p8TvlkbqgiacUGtPX+q3FwR8J4JzPyqn79HgKBds stVdKLXvIjGQd1Yb12I9OkgaCsi9+Tr2FW4G7jaoS/QtMBQa9Z/RQfAn5ty1rxiPqws3Kl3IB3dIS wWNrS4UtfR3sOwK6btO0tUJLsa/n68JhOR06EmHRp7IfYj4gNtRmidjb4dq3QjF9AY9Kyo01YH0ap AIJfuThHg==; 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 1jJbza-0000dV-R8; Wed, 01 Apr 2020 11:57:10 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jJbzY-0000cy-52 for linux-arm-kernel@lists.infradead.org; Wed, 01 Apr 2020 11:57:09 +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 398A930E; Wed, 1 Apr 2020 04:57:07 -0700 (PDT) Received: from [10.57.60.204] (unknown [10.57.60.204]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9841D3F68F; Wed, 1 Apr 2020 04:57:05 -0700 (PDT) Subject: Re: [PATCH] driver/perf: Add PMU driver for the ARM DMC-620 memory controller. To: Mark Rutland 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> <20200401102724.GA17575@willie-the-truck> <4d843ec7-ed74-4431-d8c7-d5aa6bd83c18@arm.com> <20200401112739.GD17163@C02TD0UTHF1T.local> From: Robin Murphy Message-ID: <3efa118a-5c85-6af9-e676-44087f1d398e@arm.com> Date: Wed, 1 Apr 2020 12:57:03 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200401112739.GD17163@C02TD0UTHF1T.local> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200401_045708_277836_627DEF8D X-CRM114-Status: GOOD ( 22.15 ) 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 , Will Deacon , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Tuan Phan Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2020-04-01 12:27 pm, Mark Rutland wrote: > On Wed, Apr 01, 2020 at 12:12:23PM +0100, Robin Murphy wrote: >> On 2020-04-01 11:27 am, Will Deacon wrote: >>> 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: >>>>> 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. >> >> Each PMCG is conceptually a distinct PMU with its own interrupt - for >> instance, MMU-600 has one PMCG for its TCU and one for each TBU, each with a >> distinct interrupt output signal. Of course, integrators can and will mash >> them all together into a single SPI (particularly since they're all part of >> "the SMMU"), but that boils down to the same case as here. >> >> This is going to continue to happen, so we could really do with figuring out >> a way to let MMIO system PMU drivers properly cope with shared interrupts in >> general :/ > > It does seem so, but I think we can only reasonably do that where it's > only being shared across instances of the same driver, rather than when > the IRQ is muxed across completely independent drivers. I'd like to > avoid that latter case if we can. > > The driver would have to handle migration on a cross-instance basis. > e.g. all the contexts need to be migrated before the IRQ is, to avoid a > screaming IRQ on the target CPU, or the IRQ handler on the target racing > with migration from the source. > > Is there a neat way to do that in a driver without using IRQF_SHARED, so > that we don't end up accidentally sharing with other drivers? We can > probably librify the code to handle this under drivers/pmu/. I can envision a fairly straightforward approach of flipping things upside-down such that we register a hotplug instance for the IRQ rather than the PMU, then handle the association of PMUs to IRQs internally to the driver. I believe I need to support this case in my CMN PMU driver too, so I'll prototype something there and see how it looks. Robin. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel