[PATCH v2 8/8] PCI/MSI: Allow the MSI domain to be device-specific

[Marc Zyngier <marc.zyngier@arm.com>]

So far, we've always considered that for a given PCI device, its
MSI controller was either set by the architecture-specific
pcibios hook, or simply inherited from the host bridge.

This doesn't cover things like firmware-defined topologies like
msi-map (DT) or IORT (ACPI), which can provide information about
which MSI controller to use on a per-device basis.

This patch adds the necessary hook into the MSI code to allow this
feature, and provides the msi-map functionnality as a first
implementation.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 drivers/pci/msi.c   | 17 +++++++++++++++++
 drivers/pci/probe.c |  8 ++++++++
 include/linux/msi.h |  6 ++++++
 3 files changed, 31 insertions(+)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 81a2798..3daff31 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1357,4 +1357,21 @@ u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev)
 
 	return rid;
 }
+
+/**
+ * pci_msi_get_device_domain - Get the MSI domain for a given PCI device
+ * @pdev:	The PCI device
+ *
+ * Use the firmware data to find a device-specific MSI domain
+ * (i.e. not one that is ste as a default).
+ *
+ * Returns: The coresponding MSI domain or NULL if none has been found.
+ */
+struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev)
+{
+	u32 rid = 0;
+
+	pci_for_each_dma_alias(pdev, get_msi_id_cb, &rid);
+	return of_msi_map_get_device_domain(&pdev->dev, rid);
+}
 #endif /* CONFIG_PCI_MSI_IRQ_DOMAIN */
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 7c333f8..f14a970 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1639,6 +1639,14 @@ static struct irq_domain *pci_dev_msi_domain(struct pci_dev *dev)
 	if (d)
 		return d;
 
+	/*
+	 * Let's see if we have a firmware interface able to provide
+	 * the domain.
+	 */
+	d = pci_msi_get_device_domain(dev);
+	if (d)
+		return d;
+
 	return NULL;
 }
 
diff --git a/include/linux/msi.h b/include/linux/msi.h
index 56e3b76..375be7c 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -294,6 +294,12 @@ irq_hw_number_t pci_msi_domain_calc_hwirq(struct pci_dev *dev,
 int pci_msi_domain_check_cap(struct irq_domain *domain,
 			     struct msi_domain_info *info, struct device *dev);
 u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev);
+struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev);
+#else
+static inline struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev)
+{
+	return NULL;
+}
 #endif /* CONFIG_PCI_MSI_IRQ_DOMAIN */
 
 #endif /* LINUX_MSI_H */
-- 
2.1.4