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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 C8E11C47089 for ; Thu, 27 May 2021 16:57:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A5480613D4 for ; Thu, 27 May 2021 16:57:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235252AbhE0Q6k (ORCPT ); Thu, 27 May 2021 12:58:40 -0400 Received: from foss.arm.com ([217.140.110.172]:60548 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236727AbhE0Q6g (ORCPT ); Thu, 27 May 2021 12:58:36 -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 AE63D11D4; Thu, 27 May 2021 09:57:02 -0700 (PDT) Received: from lpieralisi (e121166-lin.cambridge.arm.com [10.1.196.255]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3FD723F719; Thu, 27 May 2021 09:57:01 -0700 (PDT) Date: Thu, 27 May 2021 17:56:55 +0100 From: Lorenzo Pieralisi To: Bjorn Helgaas Cc: Will Deacon , Bjorn Helgaas , Maximilian Luz , "Rafael J. Wysocki" , Len Brown , Catalin Marinas , linux-pci@vger.kernel.org, linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] Revert "arm64: PCI: Exclude ACPI "consumer" resources from host bridge windows" Message-ID: <20210527165655.GA21788@lpieralisi> References: <20210527093200.GA16444@lpieralisi> <20210527163452.GA1402454@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210527163452.GA1402454@bjorn-Precision-5520> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Thu, May 27, 2021 at 11:34:52AM -0500, Bjorn Helgaas wrote: [...] > > > https://lore.kernel.org/r/20210510234020.1330087-1-luzmaximilian@gmail.com > > > > Sigh. We can't apply this patch since it would trigger regressions on > > other platforms (IIUC the root complex registers would end up in the > > host bridge memory windows). > > > > I am not keen on reverting commit 8fd4391ee717 because it does the > > right thing. > > > > I think this requires a quirk and immediate reporting to Microsoft. > > > > Bjorn, what are your thoughts on this ? > > In retrospect, I think 8fd4391ee717 (which I wrote), was probably a > mistake. > > Sure, it's a nice idea to have PNP0A03 _CRS methods that work nicely > as designed, by describing host bridge registers as "consumer" > resources and host bridge windows as "producer" registers, instead of > having the bridge registers in _CRS of an unrelated PNP0C02 device. > > But realistically, the PNP0A03/PNP0C02 issue is a solved problem, even > though it's ugly, and I'm not sure why I thought Microsoft would see > value in doing this differently on arm64 than on x86 and ia64. We hoped we could comply with the specs, given that we were starting from a clean slate (and not from ACPI tables cut and paste) > What would break if we reverted 8fd4391ee717? I guess any arm64 > platforms that described host bridge register space in PNP0A03 _CRS > "consumer" resources ? Yes. We would end up with that register space in the host bridge memory windows - this does not sound right. > And Windows probably doesn't work or isn't supported on those > platforms? By the look of it the answer is yes, Windows was not bootstrapped on those platforms given that I *assume* Windows does not discriminate between producer and consumer resources at all. Lorenzo