PCI: apple: Probe all GPIOs for availability first

If we're probing the PCI controller and some GPIOs are not available and
cause a probe defer, we can end up leaving some ports initialized and
not others and making a mess.

Check for PERST# GPIOs for all ports first, and just return
-EPROBE_DEFER if any are not ready yet, without bringing anything up.

Fixes: 1e33888 ("PCI: apple: Add initial hardware bring-up")
Cc: stable@vger.kernel.org
Acked-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Hector Martin <marcan@marcan.st>

Author: marcan

drivers/pci/controller/pcie-apple.c

@@ -507,6 +507,21 @@ static u32 apple_pcie_rid2sid_write(struct apple_pcie_port *port,
 	return readl_relaxed(port->base + PORT_RID2SID(idx));
 }
 
+static int apple_pcie_probe_port(struct device_node *np)
+{
+	struct gpio_desc *gd;
+
+	/* check whether the GPPIO pin exists but leave it as is */
+	gd = fwnode_gpiod_get_index(of_fwnode_handle(np), "reset", 0,
+				    GPIOD_ASIS, "PERST#");
+	if (IS_ERR(gd)) {
+		return PTR_ERR(gd);
+	}
+
+	gpiod_put(gd);
+	return 0;
+}
+
 static int apple_pcie_setup_port(struct apple_pcie *pcie,
 				 struct device_node *np)
 {
@@ -801,8 +816,19 @@ static int apple_pcie_init(struct pci_config_window *cfg)
 
 static int apple_pcie_probe(struct platform_device *pdev)
 {
+	struct device *dev = &pdev->dev;
+	struct device_node *of_port;
 	int ret;
 
+	/* Check for probe dependencies for all ports first */
+	for_each_available_child_of_node(dev->of_node, of_port) {
+		ret = apple_pcie_probe_port(of_port);
+		if (ret) {
+			of_node_put(of_port);
+			return dev_err_probe(dev, ret, "Port %pOF probe fail\n", of_port);
+		}
+	}
+
 	ret = bus_register_notifier(&pci_bus_type, &apple_pcie_nb);
 	if (ret)
 		return ret;