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,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 6D948C4332B for ; Thu, 11 Mar 2021 12:12:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4517A64FEF for ; Thu, 11 Mar 2021 12:12:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232870AbhCKMLx (ORCPT ); Thu, 11 Mar 2021 07:11:53 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232781AbhCKMLX (ORCPT ); Thu, 11 Mar 2021 07:11:23 -0500 Received: from mail.marcansoft.com (marcansoft.com [IPv6:2a01:298:fe:f::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3780DC061574; Thu, 11 Mar 2021 04:11:23 -0800 (PST) Received: from [127.0.0.1] (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: marcan@marcan.st) by mail.marcansoft.com (Postfix) with ESMTPSA id AAAD642508; Thu, 11 Mar 2021 12:11:14 +0000 (UTC) Subject: Re: [RFT PATCH v3 12/27] of/address: Add infrastructure to declare MMIO as non-posted To: Arnd Bergmann , Rob Herring Cc: linux-arm-kernel , Marc Zyngier , Olof Johansson , Krzysztof Kozlowski , Mark Kettenis , Tony Lindgren , Mohamed Mediouni , Stan Skowronek , Alexander Graf , Will Deacon , Linus Walleij , Mark Rutland , Andy Shevchenko , Greg Kroah-Hartman , Jonathan Corbet , Catalin Marinas , Christoph Hellwig , "David S. Miller" , DTML , "open list:SERIAL DRIVERS" , Linux Doc Mailing List , linux-samsung-soc , "open list:GENERIC INCLUDE/ASM HEADER FILES" , "linux-kernel@vger.kernel.org" References: <20210304213902.83903-1-marcan@marcan.st> <20210304213902.83903-13-marcan@marcan.st> <6e4880b3-1fb6-0cbf-c1a5-7a46fd9ccf62@marcan.st> <20210308211306.GA2920998@robh.at.kernel.org> <332c0b9a-dcfd-4c3b-9038-47cbda90eb3f@marcan.st> From: Hector Martin Message-ID: <7ee4a1ac-9fd4-3eca-853d-d12a16ddbb60@marcan.st> Date: Thu, 11 Mar 2021 21:11:12 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: es-ES Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/03/2021 18.12, Arnd Bergmann wrote: > On Wed, Mar 10, 2021 at 6:01 PM Rob Herring wrote: >> >> On Wed, Mar 10, 2021 at 1:27 AM Hector Martin wrote: >>> >>> On 10/03/2021 07.06, Rob Herring wrote: >>>>> My main concern here is that this creates an inconsistency in the device >>>>> tree representation that only works because PCI drivers happen not to >>>>> use these code paths. Logically, having "nonposted-mmio" above the PCI >>>>> controller would imply that it applies to that bus too. Sure, it doesn't >>>>> matter for Linux since it is ignored, but this creates an implicit >>>>> exception that PCI buses always use posted modes. >>>> >>>> We could be stricter that "nonposted-mmio" must be in the immediate >>>> parent. That's kind of in line with how addressing already works. >>>> Every level has to have 'ranges' to be an MMIO address, and the >>>> address cell size is set by the immediate parent. >>>> >>>>> Then if a device comes along that due to some twisted fabric logic needs >>>>> nonposted nGnRnE mappings for PCIe (even though the actual PCIe ops will >>>>> end up posted at the bus anyway)... how do we represent that? Declare >>>>> that another "nonposted-mmio" on the PCIe bus means "no, really, use >>>>> nonposted mmio for this"? >>>> >>>> If we're strict, yes. The PCI host bridge would have to have "nonposted-mmio". >>> >>> Works for me; then let's just make it non-recursive. >>> >>> Do you think we can get rid of the Apple-only optimization if we do >>> this? It would mean only looking at the parent during address >>> resolution, not recursing all the way to the top, so presumably the >>> performance impact would be quite minimal. > > Works for me. Incidentally, even though it would now be unused, I'd like to keep the apple,arm-platform compatible at this point; we've already been pretty close to a use case for it, and I don't want to have to fall back to a list of SoC compatibles if we ever need another quirk for all Apple ARM SoCs (or break backwards compat). It doesn't really hurt to have it in the binding and devicetrees, right? >> Yeah, that should be fine. I'd keep an IS_ENABLED() config check >> though. Then I'll also know if anyone else needs this. > > Ok, makes sense. > > Conceptually, I'd like to then see a check that verifies that the > property is only set for nodes whose parent also has it set, since > that is how AXI defines it: A bus can wait for the ack from its > child node, or it can acknowledge the write to its parent early. > However, this breaks down as soon as a bus does the early ack: > all its children by definition use posted writes (as seen by the > CPU), even if they wait for stores that come from other masters. > > Does this make sense to you? Makes sense. This shouldn't really be something the kernel concerns itself with at runtime, just something for the dts linting, right? I assume this isn't representable in json-schema, so it would presumably need some ad-hoc validation code. -- Hector Martin (marcan@marcan.st) Public Key: https://mrcn.st/pub 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,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 95772C433E0 for ; Thu, 11 Mar 2021 12:13:03 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 144E864FD9 for ; Thu, 11 Mar 2021 12:13:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 144E864FD9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=marcan.st Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+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=desiato.20200630; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:Cc:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=6sTWFmPaFnyPo2tq4QNP3cOayWV1flUiLrRzB65seLg=; b=glz3FKSEQQHqe5uFzlorHfbCM ION15CRkYSbY5l02UzxXcpISIFfWtkiXAL914RS77QOcNxiGHws4v9L/8KowuMb0dDp3koIYi75oF 5yEcfMW0hpb4lmLPp74s0w9/jc0pb5e+vqFpbW6SACuItw8TlMmQp+maBefN8XQX5jvg16cu2dN0w hXHJZrk8C+aHuGGktNL1xexMhfPalb6cynSO3C5uNXkk8NExYfZBF+6qDqOVy1dzA8l+MK+8f9Ls+ R1rDi4Acw5ZFJL3Kilv+izxS10LXvA0YZFFWyvmKiavgfh99RQoY6iAPnFka+LAQotvyjZzLSM81O yMZsoLu4g==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lKKA5-0092qH-Vl; Thu, 11 Mar 2021 12:11:30 +0000 Received: from marcansoft.com ([2a01:298:fe:f::2] helo=mail.marcansoft.com) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lKK9y-0092nM-Uk for linux-arm-kernel@lists.infradead.org; Thu, 11 Mar 2021 12:11:27 +0000 Received: from [127.0.0.1] (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: marcan@marcan.st) by mail.marcansoft.com (Postfix) with ESMTPSA id AAAD642508; Thu, 11 Mar 2021 12:11:14 +0000 (UTC) Subject: Re: [RFT PATCH v3 12/27] of/address: Add infrastructure to declare MMIO as non-posted To: Arnd Bergmann , Rob Herring Cc: linux-arm-kernel , Marc Zyngier , Olof Johansson , Krzysztof Kozlowski , Mark Kettenis , Tony Lindgren , Mohamed Mediouni , Stan Skowronek , Alexander Graf , Will Deacon , Linus Walleij , Mark Rutland , Andy Shevchenko , Greg Kroah-Hartman , Jonathan Corbet , Catalin Marinas , Christoph Hellwig , "David S. Miller" , DTML , "open list:SERIAL DRIVERS" , Linux Doc Mailing List , linux-samsung-soc , "open list:GENERIC INCLUDE/ASM HEADER FILES" , "linux-kernel@vger.kernel.org" References: <20210304213902.83903-1-marcan@marcan.st> <20210304213902.83903-13-marcan@marcan.st> <6e4880b3-1fb6-0cbf-c1a5-7a46fd9ccf62@marcan.st> <20210308211306.GA2920998@robh.at.kernel.org> <332c0b9a-dcfd-4c3b-9038-47cbda90eb3f@marcan.st> From: Hector Martin Message-ID: <7ee4a1ac-9fd4-3eca-853d-d12a16ddbb60@marcan.st> Date: Thu, 11 Mar 2021 21:11:12 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Language: es-ES X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210311_121123_568987_6C4E28F4 X-CRM114-Status: GOOD ( 31.64 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 11/03/2021 18.12, Arnd Bergmann wrote: > On Wed, Mar 10, 2021 at 6:01 PM Rob Herring wrote: >> >> On Wed, Mar 10, 2021 at 1:27 AM Hector Martin wrote: >>> >>> On 10/03/2021 07.06, Rob Herring wrote: >>>>> My main concern here is that this creates an inconsistency in the device >>>>> tree representation that only works because PCI drivers happen not to >>>>> use these code paths. Logically, having "nonposted-mmio" above the PCI >>>>> controller would imply that it applies to that bus too. Sure, it doesn't >>>>> matter for Linux since it is ignored, but this creates an implicit >>>>> exception that PCI buses always use posted modes. >>>> >>>> We could be stricter that "nonposted-mmio" must be in the immediate >>>> parent. That's kind of in line with how addressing already works. >>>> Every level has to have 'ranges' to be an MMIO address, and the >>>> address cell size is set by the immediate parent. >>>> >>>>> Then if a device comes along that due to some twisted fabric logic needs >>>>> nonposted nGnRnE mappings for PCIe (even though the actual PCIe ops will >>>>> end up posted at the bus anyway)... how do we represent that? Declare >>>>> that another "nonposted-mmio" on the PCIe bus means "no, really, use >>>>> nonposted mmio for this"? >>>> >>>> If we're strict, yes. The PCI host bridge would have to have "nonposted-mmio". >>> >>> Works for me; then let's just make it non-recursive. >>> >>> Do you think we can get rid of the Apple-only optimization if we do >>> this? It would mean only looking at the parent during address >>> resolution, not recursing all the way to the top, so presumably the >>> performance impact would be quite minimal. > > Works for me. Incidentally, even though it would now be unused, I'd like to keep the apple,arm-platform compatible at this point; we've already been pretty close to a use case for it, and I don't want to have to fall back to a list of SoC compatibles if we ever need another quirk for all Apple ARM SoCs (or break backwards compat). It doesn't really hurt to have it in the binding and devicetrees, right? >> Yeah, that should be fine. I'd keep an IS_ENABLED() config check >> though. Then I'll also know if anyone else needs this. > > Ok, makes sense. > > Conceptually, I'd like to then see a check that verifies that the > property is only set for nodes whose parent also has it set, since > that is how AXI defines it: A bus can wait for the ack from its > child node, or it can acknowledge the write to its parent early. > However, this breaks down as soon as a bus does the early ack: > all its children by definition use posted writes (as seen by the > CPU), even if they wait for stores that come from other masters. > > Does this make sense to you? Makes sense. This shouldn't really be something the kernel concerns itself with at runtime, just something for the dts linting, right? I assume this isn't representable in json-schema, so it would presumably need some ad-hoc validation code. -- Hector Martin (marcan@marcan.st) Public Key: https://mrcn.st/pub _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel