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PCI/VGA: Move non-legacy VGA detection to ADD_DEVICE path 

a37c0f4895 ("vgaarb: Select a default VGA device even if there's no
legacy VGA") extended the vga_arb_device_init() subsys_initcall so it could
select a non-legacy VGA device as the default.

That failed to consider that PCI devices may be enumerated after
vga_arb_device_init(), e.g., hot-added devices or non-ACPI systems that do
PCI enumeration in pcibios_init().  Devices found then could never be
selected as the default.

One system where this is a problem is the MIPS-based Loongson where an
ASpeed AST2500 VGA device is behind a bridge that doesn't implement the VGA
Enable bit, so legacy resources are not routed to the VGA device. [1]

Fix this by moving the non-legacy VGA 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.

[1] https://lore.kernel.org/r/20210514080025.1828197-6-chenhuacai@loongson.cn

[bhelgaas: commit log, restructure]
Link: https://lore.kernel.org/r/20211015061512.2941859-5-chenhuacai@loongson.cn
Link: https://lore.kernel.org/r/20211015061512.2941859-7-chenhuacai@loongson.cn
Link: https://lore.kernel.org/r/20220224224753.297579-7-helgaas@kernel.org
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Daniel Axtens <dja@axtens.net>
Cc: Zhou Wang <wangzhou1@hisilicon.com>
This commit is contained in:
Huacai Chen 2022-02-24 16:47:48 -06:00 committed by Bjorn Helgaas
parent f8d81df285
commit e96902eb8c
1 changed files with 32 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
drivers/pci/vgaarb.c
View File

@ -624,6 +624,7 @@ 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;
u16 cmd, boot_cmd;
/*
* We select the default VGA device in this order:
@ -661,6 +662,37 @@ static bool vga_is_boot_device(struct vga_device *vgadev)
if ((vgadev->owns & VGA_RSRC_LEGACY_MASK) == VGA_RSRC_LEGACY_MASK)
return true;
/*
* If we haven't found a legacy VGA device, accept a non-legacy
* device. It may have either IO or MEM enabled, and bridges may
* not have PCI_BRIDGE_CTL_VGA enabled, so it may not be able to
* use legacy VGA resources. Prefer an integrated GPU over others.
*/
pci_read_config_word(pdev, PCI_COMMAND, &cmd);
if (cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)) {
/*
* An integrated GPU overrides a previous non-legacy
* device. We expect only a single integrated GPU, but if
* there are more, we use the *last* because that was the
* previous behavior.
*/
if (vga_arb_integrated_gpu(&pdev->dev))
return true;
/*
* We prefer the first non-legacy discrete device we find.
* If we already found one, vgadev is no better.
*/
if (boot_vga) {
pci_read_config_word(boot_vga->pdev, PCI_COMMAND,
&boot_cmd);
if (boot_cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY))
return false;
}
return true;
}
return false;
}
@ -1529,30 +1561,8 @@ static struct miscdevice vga_arb_device = {
static void __init vga_arb_select_default_device(void)
{
struct pci_dev *pdev, *found = NULL;
struct vga_device *vgadev;
if (!vga_default_device()) {
list_for_each_entry_reverse(vgadev, &vga_list, list) {
struct device *dev = &vgadev->pdev->dev;
u16 cmd;
pdev = vgadev->pdev;
pci_read_config_word(pdev, PCI_COMMAND, &cmd);
if (cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)) {
found = pdev;
if (vga_arb_integrated_gpu(dev))
break;
}
}
}
if (found) {
vgaarb_info(&found->dev, "setting as boot device (VGA legacy resources not available)\n");
vga_set_default_device(found);
return;
}
if (!vga_default_device()) {
vgadev = list_first_entry_or_null(&vga_list,
struct vga_device, list);