[PATCH kernel] powerpc/pci/of: Parse unassigned resources

[Alexey Kardashevskiy]

The pseries platform uses the PCI_PROBE_DEVTREE method of PCI probing
which is basically reading "assigned-addresses" of every PCI device.
However if the property is missing or zero sized, then there is
no fallback of any kind and the PCI resources remain undiscovered, i.e.
pdev->resource[] array is empty.

This adds a fallback which parses the "reg" property in pretty much same
way except it marks resources as "unset" which later makes Linux assign
those resources with proper addresses.

Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
---

This is an attempts to boot linux directly under QEMU without slof/rtas;
the aim is to use petitboot instead and let the guest kernel configure
devices.

QEMU does not allocate resources, it creates correct "reg" and zero length
"assigned-addresses" (which is probably a bug on its own) which is
normally populated by SLOF later but not during this exercise.

---
 arch/powerpc/kernel/pci_of_scan.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/powerpc/kernel/pci_of_scan.c b/arch/powerpc/kernel/pci_of_scan.c
index 64ad92016b63..cfe6ec3c6aaf 100644
--- a/arch/powerpc/kernel/pci_of_scan.c
+++ b/arch/powerpc/kernel/pci_of_scan.c
@@ -82,10 +82,18 @@ static void of_pci_parse_addrs(struct device_node *node, struct pci_dev *dev)
 	const __be32 *addrs;
 	u32 i;
 	int proplen;
+	bool unset = false;
 
 	addrs = of_get_property(node, "assigned-addresses", &proplen);
 	if (!addrs)
 		return;
+	if (!addrs || !proplen) {
+		addrs = of_get_property(node, "reg", &proplen);
+		if (!addrs || !proplen)
+			return;
+		unset = true;
+	}
+
 	pr_debug("    parse addresses (%d bytes) @ %p\n", proplen, addrs);
 	for (; proplen >= 20; proplen -= 20, addrs += 5) {
 		flags = pci_parse_of_flags(of_read_number(addrs, 1), 0);
@@ -110,6 +118,8 @@ static void of_pci_parse_addrs(struct device_node *node, struct pci_dev *dev)
 			continue;
 		}
 		res->flags = flags;
+		if (unset)
+			res->flags |= IORESOURCE_UNSET;
 		res->name = pci_name(dev);
 		region.start = base;
 		region.end = base + size - 1;
-- 
2.17.1