usb: host: xhci-tegra: Enable runtime PM as late as possible

A number of things can currently go wrong after the XUSB controller has
been enabled, which means that it might need to be disabled again before
it has ever been used.

Avoid this by delaying runtime PM enablement until it's really required
right before registers are accessed for the first time.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20191206140653.2085561-8-thierry.reding@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-tegra.c

@@ -1242,27 +1242,14 @@ static int tegra_xusb_probe(struct platform_device *pdev)
 		goto put_hcd;
 	}
 
-	pm_runtime_enable(&pdev->dev);
-	if (pm_runtime_enabled(&pdev->dev))
-		err = pm_runtime_get_sync(&pdev->dev);
-	else
-		err = tegra_xusb_runtime_resume(&pdev->dev);
-
-	if (err < 0) {
-		dev_err(&pdev->dev, "failed to enable device: %d\n", err);
-		goto disable_phy;
-	}
-
-	tegra_xusb_config(tegra);
-
 	/*
 	 * The XUSB Falcon microcontroller can only address 40 bits, so set
 	 * the DMA mask accordingly.
 	 */
 	err = dma_set_mask_and_coherent(tegra->dev, DMA_BIT_MASK(40));
 	if (err < 0) {
 		dev_err(&pdev->dev, "failed to set DMA mask: %d\n", err);
-		goto put_rpm;
+		goto disable_phy;
 	}
 
 	err = tegra_xusb_request_firmware(tegra);
@@ -1271,16 +1258,30 @@ static int tegra_xusb_probe(struct platform_device *pdev)
 		goto disable_phy;
 	}
 
+	pm_runtime_enable(&pdev->dev);
+
+	if (!pm_runtime_enabled(&pdev->dev))
+		err = tegra_xusb_runtime_resume(&pdev->dev);
+	else
+		err = pm_runtime_get_sync(&pdev->dev);
+
+	if (err < 0) {
+		dev_err(&pdev->dev, "failed to enable device: %d\n", err);
+		goto free_firmware;
+	}
+
+	tegra_xusb_config(tegra);
+
 	err = tegra_xusb_load_firmware(tegra);
 	if (err < 0) {
 		dev_err(&pdev->dev, "failed to load firmware: %d\n", err);
-		goto free_firmware;
+		goto put_rpm;
 	}
 
 	err = usb_add_hcd(tegra->hcd, tegra->xhci_irq, IRQF_SHARED);
 	if (err < 0) {
 		dev_err(&pdev->dev, "failed to add USB HCD: %d\n", err);
-		goto free_firmware;
+		goto put_rpm;
 	}
 
 	device_wakeup_enable(tegra->hcd->self.controller);