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=-6.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 4C898C432BE for ; Mon, 9 Aug 2021 20:33:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2FC6560F38 for ; Mon, 9 Aug 2021 20:33:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236216AbhHIUdt (ORCPT ); Mon, 9 Aug 2021 16:33:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:39092 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234411AbhHIUdp (ORCPT ); Mon, 9 Aug 2021 16:33:45 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id B1BDB60F38; Mon, 9 Aug 2021 20:33:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628541205; bh=DFiNEUy2lvl0A6Ke0FlRdCTRadumSQO3fJWSprWIjkY=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=IPtXplkkizVttFmHqlKMMFVrf/9c28Yq43Zod3JrNDwkRD6vsFt7in9VpcExI6znz YoJLbOclV7GGtf3DQoNfEnIGkfppFNgBtwGZ4c5kOP8Ly4aW7LX/fMgTKcd4Zwi5gx DVqlkFbvbNjB2HZ8A9uVNJXUocSQb21qDkD4E+yM9p9y7mPIGwUeYwtcXWwo9itZ5p 2LOYzvN/u/RSkAhNNJ4m2D/Y6shJp3G7P7ewVxVZ1kYaehrZ6rFn+4bGJSHEEWPIZ7 XFLMY3N8Bh3e0CGavp3WrAS4smZFoIu5ySgfUXuhKQ1eNdU4kTeFeAH+VLy80TJJuZ b3tCIaSJlRbeg== Date: Mon, 9 Aug 2021 15:33:23 -0500 From: Bjorn Helgaas To: Jeremy Linton Cc: linux-pci@vger.kernel.org, lorenzo.pieralisi@arm.com, nsaenz@kernel.org, bhelgaas@google.com, rjw@rjwysocki.net, lenb@kernel.org, robh@kernel.org, kw@linux.com, f.fainelli@gmail.com, bcm-kernel-feedback-list@broadcom.com, linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rpi-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] PCI: brcmstb: Add ACPI config space quirk Message-ID: <20210809203323.GA2184624@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4d4732b9-e8df-3803-2db7-c6eef1196269@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 09, 2021 at 02:48:17PM -0500, Jeremy Linton wrote: > Hi, > > On 8/9/21 12:42 PM, Bjorn Helgaas wrote: > > On Fri, Aug 06, 2021 at 09:55:27PM -0500, Jeremy Linton wrote: > > > Hi, > > > > > > On 8/6/21 5:21 PM, Bjorn Helgaas wrote: > > > > On Thu, Aug 05, 2021 at 04:11:59PM -0500, Jeremy Linton wrote: > > > > > The PFTF CM4 is an ACPI platform that is following the PCIe SMCCC > > > > > standard because its PCIe config space isn't ECAM compliant and is > > > > > split into two parts. One part for the root port registers and a > > > > > moveable window which points at a given device's 4K config space. > > > > > Thus it doesn't have a MCFG (and really any MCFG provided would be > > > > > nonsense anyway). As Linux doesn't support the PCIe SMCCC standard > > > > > we key off a Linux specific host bridge _DSD to add custom ECAM > > > > > ops and cfgres. The cfg op selects between those two regions, as > > > > > well as disallowing problematic accesses, particularly if the link > > > > > is down because there isn't an attached device. > > > > > > > > I'm not sure SMCCC is *really* relevant here. If it is, an expansion > > > > of the acronym and a link to a spec would be helpful. > > > > > > > > But AFAICT the only important thing here is that it doesn't have > > > > standard ECAM, and we're going to work around that. > > > > > > I will reword it a bit. > > > > > > > I don't see anything about _DSD in this series. > > > > > > That is the "linux,pci-quirk" in the next patch. > > > > The next patch doesn't mention _DSD either. Is it obfuscated by > > being inside fwnode_property_read_string()? If so, it's well and > > truly hidden; I gave up trying to connect that with ACPI. > > Right, the fwnode stuff works as a DT/ACPI abstraction for reading values > from firmware tables. In this case the ACPI definition looks something like: > > Device(PCI0) { > ... > Name (_DSD, Package () { > ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), > Package () { > Package () { "linux-pcie-quirk", "bcm2711" }, > } > }) > > ... > } > > Which explains a bit of why the underlying code is a bit uh... complicated. Wow, that's ... special. I think I would include "ecam" or something in the name. There might be a variety of quirks, e.g., "P2PDMA allowed between root ports", that could reasonably fit under "linux-pcie-quirk".