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From: Marc Zyngier <maz@kernel.org>
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Bjorn Helgaas <bhelgaas@google.com>
Cc: Frank Wunderlich <frank-w@public-files.de>,
	Thierry Reding <treding@nvidia.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Rob Herring <robh@kernel.org>, Will Deacon <will@kernel.org>,
	"K. Y. Srinivasan" <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Michael Kelley <mikelley@microsoft.com>,
	Wei Liu <wei.liu@kernel.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Ryder Lee <ryder.lee@mediatek.com>,
	Marek Vasut <marek.vasut+renesas@gmail.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
	Michal Simek <michal.simek@xilinx.com>,
	Paul Walmsley <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, kernel-team@android.com
Subject: [PATCH v2 14/15] PCI/MSI: Document the various ways of ending up with NO_MSI
Date: Mon, 22 Mar 2021 18:46:13 +0000
Message-ID: <20210322184614.802565-15-maz@kernel.org> (raw)
In-Reply-To: <20210322184614.802565-1-maz@kernel.org>

We have now 4 ways of ending up with NO_MSI being set.
Document them.

Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 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)
-- 
2.29.2


  parent reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-22 18:45 [PATCH v2 00/15] PCI/MSI: Getting rid of msi_controller, and other cleanups Marc Zyngier
2021-03-22 18:46 ` [PATCH v2 01/15] PCI: tegra: Convert to MSI domains Marc Zyngier
2021-03-22 18:46 ` [PATCH v2 02/15] PCI: rcar: Don't allocate extra memory for the MSI capture address Marc Zyngier
2021-03-22 18:46 ` [PATCH v2 03/15] PCI: rcar: Convert to MSI domains Marc Zyngier
2021-03-22 18:46 ` [PATCH v2 04/15] PCI: xilinx: Don't allocate extra memory for the MSI capture address Marc Zyngier
2021-03-24 12:35   ` Bharat Kumar Gogada
2021-03-24 12:55     ` Marc Zyngier
2021-03-22 18:46 ` [PATCH v2 05/15] PCI: xilinx: Convert to MSI domains Marc Zyngier
2021-03-24 12:42   ` Bharat Kumar Gogada
2021-03-24 13:15     ` Marc Zyngier
2021-03-24 13:56       ` Bharat Kumar Gogada
2021-03-24 14:45         ` Marc Zyngier
2021-03-25  4:13           ` Bharat Kumar Gogada
2021-03-22 18:46 ` [PATCH v2 06/15] PCI: hv: Drop msi_controller structure Marc Zyngier
2021-03-22 18:46 ` [PATCH v2 07/15] PCI/MSI: Drop use of msi_controller from core code Marc Zyngier
2021-03-22 18:46 ` [PATCH v2 08/15] PCI/MSI: Kill msi_controller structure Marc Zyngier
2021-03-22 18:46 ` [PATCH v2 09/15] PCI/MSI: Kill default_teardown_msi_irqs() Marc Zyngier
2021-03-22 18:46 ` [PATCH v2 10/15] PCI/MSI: Let PCI host bridges declare their lack of MSI handling Marc Zyngier
2021-03-22 18:46 ` [PATCH v2 11/15] PCI: mediatek: Advertise " Marc Zyngier
2021-03-22 18:46 ` [PATCH v2 12/15] PCI/MSI: Let PCI host bridges declare their reliance on MSI domains Marc Zyngier
2021-03-23 11:45   ` Robin Murphy
2021-03-23 18:09     ` Marc Zyngier
2021-03-23 19:04       ` Robin Murphy
2021-03-24 13:19       ` Lorenzo Pieralisi
2021-03-24 16:11         ` Marc Zyngier
2021-03-22 18:46 ` [PATCH v2 13/15] PCI/MSI: Make pci_host_common_probe() declare its " Marc Zyngier
2021-03-22 18:46 ` Marc Zyngier [this message]
2021-03-22 18:46 ` [PATCH v2 15/15] PCI: Refactor HT advertising of NO_MSI flag Marc Zyngier

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