PCI: j721e: Initialize pcie->cdns_pcie before using it

Christian reported a NULL pointer dereference in j721e_pcie_probe() caused
by 19e86382 ("PCI: j721e: Drop redundant struct device *"), which
removed struct j721e_pcie.dev since there's another copy in struct
cdns_pcie.dev reachable via j721e_pcie->cdns_pcie->dev.

The problem is that j721e_pcie->cdns_pcie was dereferenced before being
initialized:

  j721e_pcie_probe
    pcie = devm_kzalloc()             # struct j721e_pcie
    j721e_pcie_ctrl_init(pcie)
      dev = pcie->cdns_pcie->dev      <-- dereference cdns_pcie
    switch (mode) {
    case PCI_MODE_RC:
      cdns_pcie = ...                 # alloc as part of pci_host_bridge
      pcie->cdns_pcie = cdns_pcie     <-- initialize pcie->cdns_pcie

Move the cdns_pcie initialization earlier so it is done before it is used.
This also simplifies the error exits.

Fixes: 19e86382 ("PCI: j721e: Drop redundant struct device *")
Link: https://lore.kernel.org/r/20220127222951.GA144828@bhelgaas
Link: https://lore.kernel.org/r/20220124122132.435743-1-christian.gmeiner@gmail.comReported-by: NChristian Gmeiner <christian.gmeiner@gmail.com>
Tested-by: NChristian Gmeiner <christian.gmeiner@gmail.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

drivers/pci/controller/cadence/pci-j721e.c

@@ -356,8 +356,8 @@ static int j721e_pcie_probe(struct platform_device *pdev)
 	const struct j721e_pcie_data *data;
 	struct cdns_pcie *cdns_pcie;
 	struct j721e_pcie *pcie;
-	struct cdns_pcie_rc *rc;
-	struct cdns_pcie_ep *ep;
+	struct cdns_pcie_rc *rc = NULL;
+	struct cdns_pcie_ep *ep = NULL;
 	struct gpio_desc *gpiod;
 	void __iomem *base;
 	struct clk *clk;
@@ -376,6 +376,46 @@ static int j721e_pcie_probe(struct platform_device *pdev)
 	if (!pcie)
 		return -ENOMEM;
 
+	switch (mode) {
+	case PCI_MODE_RC:
+		if (!IS_ENABLED(CONFIG_PCIE_CADENCE_HOST))
+			return -ENODEV;
+
+		bridge = devm_pci_alloc_host_bridge(dev, sizeof(*rc));
+		if (!bridge)
+			return -ENOMEM;
+
+		if (!data->byte_access_allowed)
+			bridge->ops = &cdns_ti_pcie_host_ops;
+		rc = pci_host_bridge_priv(bridge);
+		rc->quirk_retrain_flag = data->quirk_retrain_flag;
+		rc->quirk_detect_quiet_flag = data->quirk_detect_quiet_flag;
+
+		cdns_pcie = &rc->pcie;
+		cdns_pcie->dev = dev;
+		cdns_pcie->ops = &j721e_pcie_ops;
+		pcie->cdns_pcie = cdns_pcie;
+		break;
+	case PCI_MODE_EP:
+		if (!IS_ENABLED(CONFIG_PCIE_CADENCE_EP))
+			return -ENODEV;
+
+		ep = devm_kzalloc(dev, sizeof(*ep), GFP_KERNEL);
+		if (!ep)
+			return -ENOMEM;
+
+		ep->quirk_detect_quiet_flag = data->quirk_detect_quiet_flag;
+
+		cdns_pcie = &ep->pcie;
+		cdns_pcie->dev = dev;
+		cdns_pcie->ops = &j721e_pcie_ops;
+		pcie->cdns_pcie = cdns_pcie;
+		break;
+	default:
+		dev_err(dev, "INVALID device type %d\n", mode);
+		return 0;
+	}
+
 	pcie->mode = mode;
 	pcie->linkdown_irq_regfield = data->linkdown_irq_regfield;
 
@@ -426,28 +466,6 @@ static int j721e_pcie_probe(struct platform_device *pdev)
 
 	switch (mode) {
 	case PCI_MODE_RC:
-		if (!IS_ENABLED(CONFIG_PCIE_CADENCE_HOST)) {
-			ret = -ENODEV;
-			goto err_get_sync;
-		}
-
-		bridge = devm_pci_alloc_host_bridge(dev, sizeof(*rc));
-		if (!bridge) {
-			ret = -ENOMEM;
-			goto err_get_sync;
-		}
-
-		if (!data->byte_access_allowed)
-			bridge->ops = &cdns_ti_pcie_host_ops;
-		rc = pci_host_bridge_priv(bridge);
-		rc->quirk_retrain_flag = data->quirk_retrain_flag;
-		rc->quirk_detect_quiet_flag = data->quirk_detect_quiet_flag;
-
-		cdns_pcie = &rc->pcie;
-		cdns_pcie->dev = dev;
-		cdns_pcie->ops = &j721e_pcie_ops;
-		pcie->cdns_pcie = cdns_pcie;
-
 		gpiod = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
 		if (IS_ERR(gpiod)) {
 			ret = PTR_ERR(gpiod);
@@ -497,23 +515,6 @@ static int j721e_pcie_probe(struct platform_device *pdev)
 
 		break;
 	case PCI_MODE_EP:
-		if (!IS_ENABLED(CONFIG_PCIE_CADENCE_EP)) {
-			ret = -ENODEV;
-			goto err_get_sync;
-		}
-
-		ep = devm_kzalloc(dev, sizeof(*ep), GFP_KERNEL);
-		if (!ep) {
-			ret = -ENOMEM;
-			goto err_get_sync;
-		}
-		ep->quirk_detect_quiet_flag = data->quirk_detect_quiet_flag;
-
-		cdns_pcie = &ep->pcie;
-		cdns_pcie->dev = dev;
-		cdns_pcie->ops = &j721e_pcie_ops;
-		pcie->cdns_pcie = cdns_pcie;
-
 		ret = cdns_pcie_init_phy(dev, cdns_pcie);
 		if (ret) {
 			dev_err(dev, "Failed to init phy\n");
@@ -525,8 +526,6 @@ static int j721e_pcie_probe(struct platform_device *pdev)
 			goto err_pcie_setup;
 
 		break;
-	default:
-		dev_err(dev, "INVALID device type %d\n", mode);
 	}
 
 	return 0;