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>
Signed-off-by: Janne Grunau <j@jannau.net>

Author: marcan

drivers/pci/controller/pcie-apple.c

@@ -853,12 +853,36 @@ static const struct pci_ecam_ops apple_pcie_cfg_ecam_ops = {
 	}
 };
 
+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_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
+	struct device_node *of_port;
 	struct apple_pcie *pcie;
 	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);
+		}
+	}
+
 	pcie = devm_kzalloc(dev, sizeof(*pcie), GFP_KERNEL);
 	if (!pcie)
 		return -ENOMEM;