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From: Jean-Philippe Brucker <>
	Jean-Philippe Brucker <>
Subject: [PATCH] PCI/MSI: Fix MSIs for generic hosts that use device-tree's "msi-map"
Date: Mon, 10 May 2021 19:31:30 +0200	[thread overview]
Message-ID: <> (raw)

Since commit 9ec37efb8783 ("PCI/MSI: Make pci_host_common_probe()
declare its reliance on MSI domains"), platforms that rely on the
"msi-map" device-tree property don't get MSIs anymore.

On the Arm Fast Model for example [1], the host bridge doesn't have a
"msi-parent" property since it doesn't itself generate MSIs, and so
doesn't get a MSI domain. It has an "msi-map" property instead to
describe MSI controllers of child devices. As a result, due to the new
msi_domain check in pci_register_host_bridge(), the whole bus gets

Check whether the root complex has an "msi-map" property before giving
up on MSIs.

[1] arch/arm64/boot/dts/arm/fvp-base-revc.dts

Fixes: 9ec37efb8783 ("PCI/MSI: Make pci_host_common_probe() declare its reliance on MSI domains")
Signed-off-by: Jean-Philippe Brucker <>
 include/linux/pci.h | 2 ++
 drivers/pci/of.c    | 7 +++++++
 drivers/pci/probe.c | 3 ++-
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/linux/pci.h b/include/linux/pci.h
index c20211e59a57..24306504226a 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -2344,6 +2344,7 @@ int pci_vpd_find_info_keyword(const u8 *buf, unsigned int off,
 struct device_node;
 struct irq_domain;
 struct irq_domain *pci_host_bridge_of_msi_domain(struct pci_bus *bus);
+bool pci_host_of_has_msi_map(struct device *dev);
 /* Arch may override this (weak) */
 struct device_node *pcibios_get_phb_of_node(struct pci_bus *bus);
@@ -2351,6 +2352,7 @@ struct device_node *pcibios_get_phb_of_node(struct pci_bus *bus);
 #else	/* CONFIG_OF */
 static inline struct irq_domain *
 pci_host_bridge_of_msi_domain(struct pci_bus *bus) { return NULL; }
+static inline bool pci_host_of_has_msi_map(struct device *dev) { return false; }
 #endif  /* CONFIG_OF */
 static inline struct device_node *
diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index da5b414d585a..85dcb7097da4 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -103,6 +103,13 @@ struct irq_domain *pci_host_bridge_of_msi_domain(struct pci_bus *bus)
+bool pci_host_of_has_msi_map(struct device *dev)
+	if (dev && dev->of_node)
+		return of_get_property(dev->of_node, "msi-map", NULL);
+	return false;
 static inline int __of_pci_pci_compare(struct device_node *node,
 				       unsigned int data)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 3a62d09b8869..275204646c68 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -925,7 +925,8 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
-	if (bridge->msi_domain && !dev_get_msi_domain(&bus->dev))
+	if (bridge->msi_domain && !dev_get_msi_domain(&bus->dev) &&
+	    !pci_host_of_has_msi_map(parent))
 		bus->bus_flags |= PCI_BUS_FLAGS_NO_MSI;
 	if (!parent)

             reply	other threads:[~2021-05-10 17:36 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-10 17:31 Jean-Philippe Brucker [this message]
2021-05-10 18:23 ` [PATCH] PCI/MSI: Fix MSIs for generic hosts that use device-tree's "msi-map" Marc Zyngier
2021-05-11 14:12   ` Jean-Philippe Brucker
2021-05-18  8:48     ` Marc Zyngier
2021-05-25 23:40 ` Bjorn Helgaas

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