[PATCH kernel v2] powerpc/pci/of: Parse unassigned resources

[Alexey Kardashevskiy]

The pseries platform uses the PCI_PROBE_DEVTREE method of PCI probing
which reads "assigned-addresses" of every PCI device and initializes
the device resources. 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 remains empty.

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

This has an effect when:
1. a hypervisor failed to assign any resource for a device;
2. /chosen/linux,pci-probe-only=0 is in the DT so the system may try
assigning a resource.
Neither is likely to happen under PowerVM.

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.

---
Changes:
v2:
* updated commit log
* fixed a bug with checking "addrs" which made the whole patch pointless
* s/unset/mark_unset/
---
 arch/powerpc/kernel/pci_of_scan.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/pci_of_scan.c b/arch/powerpc/kernel/pci_of_scan.c
index 64ad92016b63..bd78f325a636 100644
--- a/arch/powerpc/kernel/pci_of_scan.c
+++ b/arch/powerpc/kernel/pci_of_scan.c
@@ -82,10 +82,16 @@ static void of_pci_parse_addrs(struct device_node *node, struct pci_dev *dev)
 	const __be32 *addrs;
 	u32 i;
 	int proplen;
+	bool mark_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;
+		mark_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 +116,8 @@ static void of_pci_parse_addrs(struct device_node *node, struct pci_dev *dev)
 			continue;
 		}
 		res->flags = flags;
+		if (mark_unset)
+			res->flags |= IORESOURCE_UNSET;
 		res->name = pci_name(dev);
 		region.start = base;
 		region.end = base + size - 1;
-- 
2.17.1