PCI: mvebu: Fix PCI I/O mapping creation sequence

Commit ee1604381a371 ("PCI: mvebu: Only remap I/O space if configured") had
the side effect that the PCI I/O mapping was created much earlier than
before, at a point where the probe() of the driver could still fail. This
is for example a problem if one gets an -EPROBE_DEFER at some point during
probe(), after pci_ioremap_io() has been called.

Indeed, there is currently no function to undo what pci_ioremap_io() did,
and switching to pci_remap_iospace() is not an option in pci-mvebu due to
the need for special memory attributes on Armada 38x.

Reverting ee1604381a371 ("PCI: mvebu: Only remap I/O space if configured")
would be a possibility, but it would require also reverting 42342073e38b5
("PCI: mvebu: Convert to use pci_host_bridge directly"). So instead, we use
an open-coded version of pci_host_probe() that creates the PCI I/O mapping
at a point where we are guaranteed not to fail anymore.

Fixes: ee1604381a371 ("PCI: mvebu: Only remap I/O space if configured")
Reported-by: Jan Kundrát <jan.kundrat@cesnet.cz>
Tested-by: Jan Kundrát <jan.kundrat@cesnet.cz>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

drivers/pci/controller/pci-mvebu.c

@@ -1145,7 +1145,6 @@ static int mvebu_pcie_parse_request_resources(struct mvebu_pcie *pcie)
 {
 	struct device *dev = &pcie->pdev->dev;
 	struct device_node *np = dev->of_node;
-	unsigned int i;
 	int ret;
 
 	INIT_LIST_HEAD(&pcie->resources);
@@ -1179,13 +1178,58 @@ static int mvebu_pcie_parse_request_resources(struct mvebu_pcie *pcie)
 					 resource_size(&pcie->io) - 1);
 		pcie->realio.name = "PCI I/O";
 
+		pci_add_resource(&pcie->resources, &pcie->realio);
+	}
+
+	return devm_request_pci_bus_resources(dev, &pcie->resources);
+}
+
+/*
+ * This is a copy of pci_host_probe(), except that it does the I/O
+ * remap as the last step, once we are sure we won't fail.
+ *
+ * It should be removed once the I/O remap error handling issue has
+ * been sorted out.
+ */
+static int mvebu_pci_host_probe(struct pci_host_bridge *bridge)
+{
+	struct mvebu_pcie *pcie;
+	struct pci_bus *bus, *child;
+	int ret;
+
+	ret = pci_scan_root_bus_bridge(bridge);
+	if (ret < 0) {
+		dev_err(bridge->dev.parent, "Scanning root bridge failed");
+		return ret;
+	}
+
+	pcie = pci_host_bridge_priv(bridge);
+	if (resource_size(&pcie->io) != 0) {
+		unsigned int i;
+
 		for (i = 0; i < resource_size(&pcie->realio); i += SZ_64K)
 			pci_ioremap_io(i, pcie->io.start + i);
+	}
 
-		pci_add_resource(&pcie->resources, &pcie->realio);
+	bus = bridge->bus;
+
+	/*
+	 * We insert PCI resources into the iomem_resource and
+	 * ioport_resource trees in either pci_bus_claim_resources()
+	 * or pci_bus_assign_resources().
+	 */
+	if (pci_has_flag(PCI_PROBE_ONLY)) {
+		pci_bus_claim_resources(bus);
+	} else {
+		pci_bus_size_bridges(bus);
+		pci_bus_assign_resources(bus);
+
+		list_for_each_entry(child, &bus->children, node)
+			pcie_bus_configure_settings(child);
 	}
 
-	return devm_request_pci_bus_resources(dev, &pcie->resources);
+	pci_bus_add_devices(bus);
+	return 0;
 }
 
 static int mvebu_pcie_probe(struct platform_device *pdev)
@@ -1268,7 +1312,7 @@ static int mvebu_pcie_probe(struct platform_device *pdev)
 	bridge->align_resource = mvebu_pcie_align_resource;
 	bridge->msi = pcie->msi;
 
-	return pci_host_probe(bridge);
+	return mvebu_pci_host_probe(bridge);
 }
 
 static const struct of_device_id mvebu_pcie_of_match_table[] = {