vgaarb: Factor out EFI and fallback default device selection

The default VGA device is normally set in vga_arbiter_add_pci_device() when
we call it for the first enabled device that can be accessed with the
legacy VGA resources ([mem 0xa0000-0xbffff], etc.)

That default device can be overridden by an EFI device that owns the boot
framebuffer.  As a fallback, we can also select a VGA device that can't be
accessed via legacy VGA resources, or a VGA device that isn't even enabled.

Factor out this EFI and fallback selection from vga_arb_device_init() into
a separate vga_arb_select_default_device() function.  This doesn't change
any behavior, but it untangles the "bridge control possible" checking and
messages from the default device selection.

Tested-by: Zhou Wang <wangzhou1@hisilicon.com>  # D05 Hisi Hip07, Hip08
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20171013034729.14630.30419.stgit@bhelgaas-glaptop.roam.corp.google.com

drivers/gpu/vga/vgaarb.c

@@ -1402,29 +1402,14 @@ static struct miscdevice vga_arb_device = {
 	MISC_DYNAMIC_MINOR, "vga_arbiter", &vga_arb_device_fops
 };
 
-static int __init vga_arb_device_init(void)
+static void __init vga_arb_select_default_device(void)
 {
-	int rc;
 	struct pci_dev *pdev;
 	struct vga_device *vgadev;
 
-	rc = misc_register(&vga_arb_device);
-	if (rc < 0)
-		pr_err("error %d registering device\n", rc);
-
-	bus_register_notifier(&pci_bus_type, &pci_notifier);
-
-	/* We add all pci devices satisfying vga class in the arbiter by
-	 * default */
-	pdev = NULL;
-	while ((pdev =
-		pci_get_subsys(PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID,
-			       PCI_ANY_ID, pdev)) != NULL)
-		vga_arbiter_add_pci_device(pdev);
-
+#if defined(CONFIG_X86) || defined(CONFIG_IA64)
 	list_for_each_entry(vgadev, &vga_list, list) {
 		struct device *dev = &vgadev->pdev->dev;
-#if defined(CONFIG_X86) || defined(CONFIG_IA64)
 		/*
 		 * Override vga_arbiter_add_pci_device()'s I/O based detection
 		 * as it may take the wrong device (e.g. on Apple system under
@@ -1461,12 +1446,8 @@ static int __init vga_arb_device_init(void)
 				vgaarb_info(dev, "overriding boot device\n");
 			vga_set_default_device(vgadev->pdev);
 		}
-#endif
-		if (vgadev->bridge_has_one_vga)
-			vgaarb_info(dev, "bridge control possible\n");
-		else
-			vgaarb_info(dev, "no bridge control possible\n");
 	}
+#endif
 
 	if (!vga_default_device()) {
 		list_for_each_entry(vgadev, &vga_list, list) {
@@ -1492,6 +1473,38 @@ static int __init vga_arb_device_init(void)
 			vga_set_default_device(vgadev->pdev);
 		}
 	}
+}
+
+static int __init vga_arb_device_init(void)
+{
+	int rc;
+	struct pci_dev *pdev;
+	struct vga_device *vgadev;
+
+	rc = misc_register(&vga_arb_device);
+	if (rc < 0)
+		pr_err("error %d registering device\n", rc);
+
+	bus_register_notifier(&pci_bus_type, &pci_notifier);
+
+	/* We add all PCI devices satisfying VGA class in the arbiter by
+	 * default */
+	pdev = NULL;
+	while ((pdev =
+		pci_get_subsys(PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID,
+			       PCI_ANY_ID, pdev)) != NULL)
+		vga_arbiter_add_pci_device(pdev);
+
+	list_for_each_entry(vgadev, &vga_list, list) {
+		struct device *dev = &vgadev->pdev->dev;
+
+		if (vgadev->bridge_has_one_vga)
+			vgaarb_info(dev, "bridge control possible\n");
+		else
+			vgaarb_info(dev, "no bridge control possible\n");
+	}
+
+	vga_arb_select_default_device();
 
 	pr_info("loaded\n");
 	return rc;