[PATCH 15/17] pci: of_property: Add the interrupt-controller property in PCI device nodes

[Herve Codina]

PCI devices and bridges DT nodes created during the PCI scan are created
with the interrupt-map property set to handle interrupts.

In order to set this interrupt-map property at a specific level, a
phandle to the parent interrupt controller is needed.
On systems that are not fully described by a device-tree, the parent
interrupt controller may be unavailable (i.e. not described by the
device-tree).

As mentioned in the [1], avoiding the use of the interrupt-map property
and considering a PCI device as an interrupt controller itself avoid the
use of a parent interrupt phandle.

In that case, the PCI device itself as an interrupt controller is
responsible for routing the interrupts described in the device-tree
world (DT overlay) to the PCI interrupts.

Add the 'interrupt-controller' property in the PCI device DT node.

[1]: https://lore.kernel.org/lkml/CAL_Jsq+je7+9ATR=B6jXHjEJHjn24vQFs4Tvi9=vhDeK9n42Aw@xxxxxxxxxxxxxx/

Signed-off-by: Herve Codina <herve.codina@xxxxxxxxxxx>
---
 drivers/pci/of_property.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/pci/of_property.c b/drivers/pci/of_property.c
index c2c7334152bc..9f8b940029ed 100644
--- a/drivers/pci/of_property.c
+++ b/drivers/pci/of_property.c
@@ -183,6 +183,26 @@ static int of_pci_prop_interrupts(struct pci_dev *pdev,
 	return of_changeset_add_prop_u32(ocs, np, "interrupts", (u32)pin);
 }
 
+static int of_pci_prop_intr_ctrl(struct pci_dev *pdev, struct of_changeset *ocs,
+				 struct device_node *np)
+{
+	int ret;
+	u8 pin;
+
+	ret = pci_read_config_byte(pdev, PCI_INTERRUPT_PIN, &pin);
+	if (ret != 0)
+		return ret;
+
+	if (!pin)
+		return 0;
+
+	ret = of_changeset_add_prop_u32(ocs, np, "#interrupt-cells", 1);
+	if (ret)
+		return ret;
+
+	return of_changeset_add_prop_bool(ocs, np, "interrupt-controller");
+}
+
 static int of_pci_prop_intr_map(struct pci_dev *pdev, struct of_changeset *ocs,
 				struct device_node *np)
 {
@@ -334,6 +354,10 @@ int of_pci_add_properties(struct pci_dev *pdev, struct of_changeset *ocs,
 		ret = of_pci_prop_intr_map(pdev, ocs, np);
 		if (ret)
 			return ret;
+	} else {
+		ret = of_pci_prop_intr_ctrl(pdev, ocs, np);
+		if (ret)
+			return ret;
 	}
 
 	ret = of_pci_prop_ranges(pdev, ocs, np);
-- 
2.44.0