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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1509BC433EF for ; Wed, 12 Jan 2022 21:10:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233090AbiALVKp (ORCPT ); Wed, 12 Jan 2022 16:10:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56404 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232929AbiALVKn (ORCPT ); Wed, 12 Jan 2022 16:10:43 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 481FAC06173F; Wed, 12 Jan 2022 13:10:43 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 12A86B820E0; Wed, 12 Jan 2022 21:10:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96DFBC36AEC; Wed, 12 Jan 2022 21:10:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1642021840; bh=SCZfVDR/DICg7y5IJblkJMpx8rF2UrcotY0FTQsBNIM=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=OtZhi9pUdFOilXiB6ELZse0nJGGd5JwmUVEL9PMrHkaJagrI5ox4Q49dF+QKh6Woj IijpluplthICPpbrTyxLyA1l/zN+T2kHTIYSWY+cj7E3B6LjLX/wi3ycN0ytrGsaYn 9B+vbNoHhbQPE8wQ6EJTAvEgFm9KXMXO0wN+brStXb8afQtECWAdv5vNSItGcdJ+f1 pKXIUirQGZldwdD0JWYIvSuLQ3GRJ+geylot0obCONi9OztVsM3G0n9wk1r7+Gza7s HZnDufyqVRVVg3kP8W5CnnUJ3ENynAtCPToEkCWoMR6GWQoCH+djE5aZ6JA5JNLNeL 5DYQMUsfOBVVw== Date: Wed, 12 Jan 2022 15:10:39 -0600 From: Bjorn Helgaas To: Jiaxun Yang Cc: Rob Herring , Lorenzo Pieralisi , Jonathan Hunter , Thierry Reding , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Tiezhu Yang , Huacai Chen , Ray Jui , Scott Branden , bcm-kernel-feedback-list@broadcom.com, linux-arm-kernel@lists.infradead.org, linux-pci , linux-tegra@vger.kernel.org Subject: Re: [PATCH 19/19] PCI: Set bridge map_irq and swizzle_irq to default functions Message-ID: <20220112211039.GA281591@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <84d849b5-9386-4db5-87fe-34de3d6c487b@www.fastmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org On Wed, Jan 12, 2022 at 08:08:45PM +0000, Jiaxun Yang wrote: > 在2022年1月12日一月 下午3:19，Bjorn Helgaas写道： > > On Wed, Jan 12, 2022 at 12:57:44PM +0000, Jiaxun Yang wrote: > >> 在2022年1月11日一月 下午9:46，Bjorn Helgaas写道： > >> > [-cc many, +cc iproc, loongson, tegra maintainers] > [...] > > I see these: > > > > Documentation/devicetree/bindings/pci/loongson.yaml > > arch/mips/boot/dts/loongson/rs780e-pch.dtsi > > > > which makes me think there are Loongson systems with DT. Are there > > some Loongson systems with DT and some legacy ones without? > > Actually all present MIPS/Loongson systems are legacy and we just > built-in DTs in kernel and select which one to use at boot time. So I guess you know enough about what platform it is to select which DT to use, but you don't know enough to know the I8259 routing? If you *could* select a DT that described the I8259 routing, I guess maybe you could select a matching DT or update a DT in-place? > > The only driver I see is drivers/pci/controller/pci-loongson.c. > > Is that used for all Loongson system? It unconditionally uses > > ->map_irq = loongson_map_irq(). > > Yes, it's used among all Loongson systems. For system using LS7A > PCH the IRQ mapping is fixed so we just programmed it in DT. For > RS780E we use this routine to read PCI_INTERRUPT_LINE to select > which I8259 IRQ to use. > > > loongson_map_irq() reads PCI_INTERRUPT_LINE; I think that depends > > on firmware having previously programmed it, right? > > I'm unclear about what did firmware do but as AMD RS780E is used in > x86 PCs as well it should be the same way. PCI devices don't use the value in PCI_INTERRUPT_LINE, and the spec doesn't define a default value. It's only for use by software. I'm pretty sure that on ACPI x86, we don't depend on PCI_INTERRUPT_LINE except for things like quirks. I think the ACPI MADT and _PRT are supposed to contain all the INTx routing information we need. Obviously this isn't an ACPI system. I'm just making the point that it *should* be possible to remove this dependency on firmware if we can identify the specific platform (which determines the I8259 routing). Bjorn