powerpc/pasemi: Add PCI initialisation for Nemo board.

The A-Eon Amigaone X1000's Nemo motherboard has an AMD SB600
connected to one of the PCI-e root ports on its PaSemi
Pwrficient 1628M SoC. Normally the SB600 southbridge would be
connected to a hidden PCI-e port on the system's northbridge,
and as a result doesn't fully comply with the PCI-e spec.

Add code to relax the PCI-e detection in both the root port
and the Linux kernel allowing on board devices to be detected.
Signed-off-by: Darren Stevens <darren@stevens-zone.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/pasemi/pci.c

@@ -108,6 +108,61 @@ static int workaround_5945(struct pci_bus *bus, unsigned int devfn,
 	return 1;
 }
 
+#ifdef CONFIG_PPC_PASEMI_NEMO
+#define PXP_ERR_CFG_REG	0x4
+#define PXP_IGNORE_PCIE_ERRORS	0x800
+#define SB600_BUS 5
+
+static void sb600_set_flag(int bus)
+{
+	static void __iomem *iob_mapbase = NULL;
+	struct resource res;
+	struct device_node *dn;
+	int err;
+
+	if (iob_mapbase == NULL) {
+		dn = of_find_compatible_node(NULL, "isa", "pasemi,1682m-iob");
+		if (!dn) {
+			pr_crit("NEMO SB600 missing iob node\n");
+			return;
+		}
+
+		err = of_address_to_resource(dn, 0, &res);
+		of_node_put(dn);
+
+		if (err) {
+			pr_crit("NEMO SB600 missing resource\n");
+			return;
+		}
+
+		pr_info("NEMO SB600 IOB base %08llx\n",res.start);
+
+		iob_mapbase = ioremap(res.start + 0x100, 0x94);
+	}
+
+	if (iob_mapbase != NULL) {
+		if (bus == SB600_BUS) {
+			/*
+			 * This is the SB600's bus, tell the PCI-e root port
+			 * to allow non-zero devices to enumerate.
+			 */
+			out_le32(iob_mapbase + PXP_ERR_CFG_REG, in_le32(iob_mapbase + PXP_ERR_CFG_REG) | PXP_IGNORE_PCIE_ERRORS);
+		} else {
+			/*
+			 * Only scan device 0 on other busses
+			 */
+			out_le32(iob_mapbase + PXP_ERR_CFG_REG, in_le32(iob_mapbase + PXP_ERR_CFG_REG) & ~PXP_IGNORE_PCIE_ERRORS);
+		}
+	}
+}
+
+#else
+
+static void sb600_set_flag(int bus)
+{
+}
+#endif
+
 static int pa_pxp_read_config(struct pci_bus *bus, unsigned int devfn,
 			      int offset, int len, u32 *val)
 {