[PATCH 1/2] of_pci_irq: add a check to fallback to standard device tree parsing

[Ryder Lee <ryder.lee@mediatek.com>]

A root complex usually consist of a host bridge and multiple P2P bridges,
and someone may express that in the form of a root node with many subnodes
and list all four interrupts for each slot (child node) in the root node
like this:

	pcie-controller {
		...
		interrupt-map-mask = <0xf800 0 0 7>;
		interrupt-map = <0x0000 0 0 {INTx} &{interrupt parent} ...>
				 0x0800 0 0 {INTx} &{interrupt parent} ...>;

		pcie@0,0 {
			reg = <0x0000 0 0 0 0>;
			...
		};

		pcie@1,0 {
			reg = <0x0800 0 0 0 0>;
			...
		};
	};

As shown above, we'd like to propagate IRQs from a root port to the devices
in the hierarchy below it in this way.  However, it seems that the current
parser couldn't handle such cases and will get something unexpected below:

	pcieport 0000:00:01.0: assign IRQ: got 213
	igb 0000:01:00.0: assign IRQ: got 212

There is a device which is connected to 2nd slot, but the port doesn't share
the same IRQ with its downstream devices.  The problem here is that, if the
loop found a P2P bridge, it wouldn't check whether the reg property exists
in ppnode or not but just pass the subordinate devfn to of_irq_parse_raw(),
thus the subsequent flow couldn't correctly resolve them.

Fix this by adding a check to fallback to standard device tree parsing.

Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
---
Please refer to the previous discussion thread: https://patchwork.ozlabs.org/patch/829108/
---
 drivers/of/of_pci_irq.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/of/of_pci_irq.c b/drivers/of/of_pci_irq.c
index 3a05568..e445866 100644
--- a/drivers/of/of_pci_irq.c
+++ b/drivers/of/of_pci_irq.c
@@ -86,8 +86,18 @@ int of_irq_parse_pci(const struct pci_dev *pdev, struct of_phandle_args *out_irq
 	out_irq->np = ppnode;
 	out_irq->args_count = 1;
 	out_irq->args[0] = pin;
-	laddr[0] = cpu_to_be32((pdev->bus->number << 16) | (pdev->devfn << 8));
-	laddr[1] = laddr[2] = cpu_to_be32(0);
+
+	if (!dn && ppnode) {
+		const __be32 *addr;
+
+		addr = of_get_property(ppnode, "reg", NULL);
+		if (addr)
+			memcpy(laddr, addr, 3);
+	} else {
+		laddr[0] = cpu_to_be32((pdev->bus->number << 16) | (pdev->devfn << 8));
+		laddr[1] = laddr[2] = cpu_to_be32(0);
+	}
+
 	rc = of_irq_parse_raw(laddr, out_irq);
 	if (rc)
 		goto err;
-- 
1.9.1