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authorHuacai Chen <chenhuacai@loongson.cn>2022-02-25 01:47:46 +0300
committerBjorn Helgaas <bhelgaas@google.com>2022-03-10 03:31:02 +0300
commitdfe3da812d99b40f99ce018152db4b3a87bd86c4 (patch)
treedec7db70637e84812fb65373f79f9fb6c8a30a25 /drivers/pci/vgaarb.c
parent60a9bac8ab48ddbf68dc280cd26879583e9d72ba (diff)
downloadlinux-dfe3da812d99b40f99ce018152db4b3a87bd86c4.tar.xz
PCI/VGA: Factor out default VGA device selection
Default VGA device selection fails when PCI devices are enumerated after the vga_arb_device_init() subsys_initcall. vga_arbiter_add_pci_device() selects the first fully enabled device to which legacy VGA resources are routed as the default VGA device. This is an ADD_DEVICE notifier, so it runs after every PCI device is enumerated. vga_arb_select_default_device() may select framebuffer devices, partially enabled GPUs, or non-legacy devices that don't have legacy VGA resources routed to them as the default VGA device. But this only happens once, from the vga_arb_device_init() subsys_initcall, so it doesn't consider devices enumerated after that: acpi_init acpi_scan_init acpi_pci_root_init # PCI device enumeration (ACPI systems) vga_arb_device_init for_each_pci_device vga_arbiter_add_pci_device # ADD_DEVICE notifier if (VGA-owner) vga_set_default_device <-- set default VGA vga_arb_select_default_device # only called ONCE for_each_vga_device if (framebuffer) vga_set_default_device <-- set default VGA to framebuffer if (!vga_default_device()) if (non-legacy, integrated GPU, etc) vga_set_default_device <-- set default VGA if (!vga_default_device()) vga_set_default_device <-- set default VGA pcibios_init pcibios_scanbus # PCI device enumeration (non-ACPI systems) ... vga_arbiter_add_pci_device # ADD_DEVICE notification if (VGA-owner) vga_set_default_device <-- set default VGA Note that on non-ACPI systems, vga_arb_select_default_device() runs before pcibios_init(), so it sees no VGA devices and can never set a framebuffer device, a non-legacy integrated GPU, etc., as the default device. Factor out the default VGA device selection to vga_is_boot_device(), called from vga_arbiter_add_pci_device(). Then we can migrate the default device selection from vga_arb_select_default_device() to the vga_arbiter_add_pci_device() path. [bhelgaas: commit log, split to separate patch] Link: https://lore.kernel.org/r/20211015061512.2941859-4-chenhuacai@loongson.cn Link: https://lore.kernel.org/r/20220224224753.297579-5-helgaas@kernel.org Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Diffstat (limited to 'drivers/pci/vgaarb.c')
-rw-r--r--drivers/pci/vgaarb.c45
1 files changed, 39 insertions, 6 deletions
diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c
index 3f8fead49197..58e0a12e623b 100644
--- a/drivers/pci/vgaarb.c
+++ b/drivers/pci/vgaarb.c
@@ -629,6 +629,41 @@ static bool vga_arb_integrated_gpu(struct device *dev)
}
/*
+ * Return true if vgadev is a better default VGA device than the best one
+ * we've seen so far.
+ */
+static bool vga_is_boot_device(struct vga_device *vgadev)
+{
+ struct vga_device *boot_vga = vgadev_find(vga_default_device());
+
+ /*
+ * We select the default VGA device in this order:
+ * Firmware framebuffer (see vga_arb_select_default_device())
+ * Legacy VGA device (owns VGA_RSRC_LEGACY_MASK)
+ * Non-legacy integrated device (see vga_arb_select_default_device())
+ * Non-legacy discrete device (see vga_arb_select_default_device())
+ * Other device (see vga_arb_select_default_device())
+ */
+
+ /*
+ * A legacy VGA device has MEM and IO enabled and any bridges
+ * leading to it have PCI_BRIDGE_CTL_VGA enabled so the legacy
+ * resources ([mem 0xa0000-0xbffff], [io 0x3b0-0x3bb], etc) are
+ * routed to it.
+ *
+ * We use the first one we find, so if we've already found one,
+ * vgadev is no better.
+ */
+ if (boot_vga)
+ return false;
+
+ if ((vgadev->owns & VGA_RSRC_LEGACY_MASK) == VGA_RSRC_LEGACY_MASK)
+ return true;
+
+ return false;
+}
+
+/*
* Rules for using a bridge to control a VGA descendant decoding: if a bridge
* has only one VGA descendant then it can be used to control the VGA routing
* for that device. It should always use the bridge closest to the device to
@@ -755,12 +790,10 @@ static bool vga_arbiter_add_pci_device(struct pci_dev *pdev)
bus = bus->parent;
}
- /* Deal with VGA default device. Use first enabled one
- * by default if arch doesn't have it's own hook
- */
- if (vga_default == NULL &&
- ((vgadev->owns & VGA_RSRC_LEGACY_MASK) == VGA_RSRC_LEGACY_MASK)) {
- vgaarb_info(&pdev->dev, "setting as boot VGA device\n");
+ if (vga_is_boot_device(vgadev)) {
+ vgaarb_info(&pdev->dev, "setting as boot VGA device%s\n",
+ vga_default_device() ?
+ " (overriding previous)" : "");
vga_set_default_device(pdev);
}