PCI/VGA: Move firmware default device detection to ADD_DEVICE path

Previously we selected the firmware default device, i.e., one that owns the
boot framebuffer, as the default device in vga_arb_select_default_device().
This was only done in the vga_arb_device_init() subsys_initcall, so devices
enumerated later, e.g., by pcibios_init(), were not eligible.

Fix this by moving the firmware default device selection from
vga_arb_select_default_device() to vga_arbiter_add_pci_device(), which is
called after every PCI device is enumerated, either by the
vga_arb_device_init() subsys_initcall or as an ADD_DEVICE notifier.

Note that if vga_arb_select_default_device() previously found a device
owning the boot framebuffer, it unconditionally set it to be the default
VGA device, and no subsequent device could replace it.

[bhelgaas: commit log, restructure slightly]
Link: https://lore.kernel.org/r/20211015061512.2941859-7-chenhuacai@loongson.cn
Link: https://lore.kernel.org/r/20220224224753.297579-6-helgaas@kernel.org
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Bruno Prémont <bonbons@linux-vserver.org>

Author: chenhuacai

drivers/pci/vgaarb.c

@@ -72,6 +72,7 @@ struct vga_device {
 	unsigned int io_norm_cnt;	/* normal IO count */
 	unsigned int mem_norm_cnt;	/* normal MEM count */
 	bool bridge_has_one_vga;
+	bool is_firmware_default;	/* device selected by firmware */
 	unsigned int (*set_decode)(struct pci_dev *pdev, bool decode);
 };
 
@@ -565,10 +566,9 @@ void vga_put(struct pci_dev *pdev, unsigned int rsrc)
 }
 EXPORT_SYMBOL(vga_put);
 
-static void __init vga_select_framebuffer_device(struct pci_dev *pdev)
+static bool vga_is_firmware_default(struct pci_dev *pdev)
 {
 #if defined(CONFIG_X86) || defined(CONFIG_IA64)
-	struct device *dev = &pdev->dev;
 	u64 base = screen_info.lfb_base;
 	u64 size = screen_info.lfb_size;
 	u64 limit;
@@ -583,15 +583,6 @@ static void __init vga_select_framebuffer_device(struct pci_dev *pdev)
 
 	limit = base + size;
 
-	/*
-	 * Override vga_arbiter_add_pci_device()'s I/O based detection
-	 * as it may take the wrong device (e.g. on Apple system under
-	 * EFI).
-	 *
-	 * Select the device owning the boot framebuffer if there is
-	 * one.
-	 */
-
 	/* Does firmware framebuffer belong to us? */
 	for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
 		flags = pci_resource_flags(pdev, i);
@@ -608,13 +599,10 @@ static void __init vga_select_framebuffer_device(struct pci_dev *pdev)
 		if (base < start || limit >= end)
 			continue;
 
-		if (!vga_default_device())
-			vgaarb_info(dev, "setting as boot device\n");
-		else if (pdev != vga_default_device())
-			vgaarb_info(dev, "overriding boot device\n");
-		vga_set_default_device(pdev);
+		return true;
 	}
 #endif
+	return false;
 }
 
 static bool vga_arb_integrated_gpu(struct device *dev)
@@ -635,6 +623,7 @@ static bool vga_arb_integrated_gpu(struct device *dev)
 static bool vga_is_boot_device(struct vga_device *vgadev)
 {
 	struct vga_device *boot_vga = vgadev_find(vga_default_device());
+	struct pci_dev *pdev = vgadev->pdev;
 
 	/*
 	 * We select the default VGA device in this order:
@@ -645,6 +634,18 @@ static bool vga_is_boot_device(struct vga_device *vgadev)
 	 *   Other device (see vga_arb_select_default_device())
 	 */
 
+	/*
+	 * We always prefer a firmware default device, so if we've already
+	 * found one, there's no need to consider vgadev.
+	 */
+	if (boot_vga && boot_vga->is_firmware_default)
+		return false;
+
+	if (vga_is_firmware_default(pdev)) {
+		vgadev->is_firmware_default = true;
+		return true;
+	}
+
 	/*
 	 * A legacy VGA device has MEM and IO enabled and any bridges
 	 * leading to it have PCI_BRIDGE_CTL_VGA enabled so the legacy
@@ -1531,10 +1532,6 @@ static void __init vga_arb_select_default_device(void)
 	struct pci_dev *pdev, *found = NULL;
 	struct vga_device *vgadev;
 
-	list_for_each_entry(vgadev, &vga_list, list) {
-		vga_select_framebuffer_device(vgadev->pdev);
-	}
-
 	if (!vga_default_device()) {
 		list_for_each_entry_reverse(vgadev, &vga_list, list) {
 			struct device *dev = &vgadev->pdev->dev;