From patchwork Thu Feb 25 15:10:22 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Zyngier X-Patchwork-Id: 1444487 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-pci-owner@vger.kernel.org; receiver=) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4Dmc5z2y43z9sBJ for ; Fri, 26 Feb 2021 02:24:39 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230166AbhBYPY0 (ORCPT ); Thu, 25 Feb 2021 10:24:26 -0500 Received: from mail.kernel.org ([198.145.29.99]:43258 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229800AbhBYPYV (ORCPT ); Thu, 25 Feb 2021 10:24:21 -0500 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AD84864F11; Thu, 25 Feb 2021 15:23:39 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.lan) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94) (envelope-from ) id 1lFIII-00Fscv-RS; Thu, 25 Feb 2021 15:11:11 +0000 From: Marc Zyngier To: Lorenzo Pieralisi , Bjorn Helgaas Cc: Frank Wunderlich , Thierry Reding , Thomas Gleixner , Rob Herring , Will Deacon , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu , Thierry Reding , Jonathan Hunter , Ryder Lee , Marek Vasut , Yoshihiro Shimoda , Michal Simek , Paul Walmsley , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-hyperv@vger.kernel.org, linux-tegra@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-renesas-soc@vger.kernel.org Subject: [PATCH 12/13] PCI: MSI: Document the various ways of ending up with NO_MSI Date: Thu, 25 Feb 2021 15:10:22 +0000 Message-Id: <20210225151023.3642391-13-maz@kernel.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210225151023.3642391-1-maz@kernel.org> References: <20210225151023.3642391-1-maz@kernel.org> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: lorenzo.pieralisi@arm.com, bhelgaas@google.com, frank-w@public-files.de, treding@nvidia.com, tglx@linutronix.de, robh@kernel.org, will@kernel.org, kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com, wei.liu@kernel.org, thierry.reding@gmail.com, jonathanh@nvidia.com, ryder.lee@mediatek.com, marek.vasut+renesas@gmail.com, yoshihiro.shimoda.uh@renesas.com, michal.simek@xilinx.com, paul.walmsley@sifive.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-hyperv@vger.kernel.org, linux-tegra@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-renesas-soc@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org We have now 4 ways of ending up with NO_MSI being set. Document them. Signed-off-by: Marc Zyngier --- drivers/pci/msi.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c index d9c73c173c14..425abcdfcaca 100644 --- a/drivers/pci/msi.c +++ b/drivers/pci/msi.c @@ -871,8 +871,16 @@ static int pci_msi_supported(struct pci_dev *dev, int nvec) * Any bridge which does NOT route MSI transactions from its * secondary bus to its primary bus must set NO_MSI flag on * the secondary pci_bus. - * We expect only arch-specific PCI host bus controller driver - * or quirks for specific PCI bridges to be setting NO_MSI. + * + * The NO_MSI flag can either be set directly by: + * - arch-specific PCI host bus controller drivers (deprecated) + * - quirks for specific PCI bridges + * + * or indirectly by platform-specific PCI host bridge drivers by: + * - unconditionally advertising the 'no_msi' property + * - advertising the 'msi_domain' property, which results in + * the NO_MSI flag when no MSI domain is found for this bridge + * at probe time. */ for (bus = dev->bus; bus; bus = bus->parent) if (bus->bus_flags & PCI_BUS_FLAGS_NO_MSI)