From: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Current default VGA device selection fails in some cases because part of it
is done in the vga_arb_device_init() subsys_initcall, and some arches
enumerate PCI devices in pcibios_init(), which runs *after* that.
For example:
- On BMC system, the AST2500 bridge [1a03:1150] does not implement
PCI_BRIDGE_CTL_VGA. This is perfectly legal but means the legacy VGA
resources won't reach downstream devices unless they're included in the
usual bridge windows.
- vga_arb_select_default_device() will set a device below such a bridge
as the default VGA device as long as it has PCI_COMMAND_IO and
PCI_COMMAND_MEMORY enabled.
- vga_arbiter_add_pci_device() is called for every VGA device, either at
boot-time or at hot-add time, and it will also set the device as the
default VGA device, but ONLY if all bridges leading to it implement
PCI_BRIDGE_CTL_VGA.
- This difference between vga_arb_select_default_device() and
vga_arbiter_add_pci_device() means that a device below an AST2500 or
similar bridge can only be set as the default if it is enumerated
before vga_arb_device_init().
- On ACPI-based systems, PCI devices are enumerated by acpi_init(), which
runs before vga_arb_device_init().
- On non-ACPI systems, like on MIPS system, they are enumerated by
pcibios_init(), which typically runs *after* vga_arb_device_init().
This series consolidates all the default VGA device selection in
vga_arbiter_add_pci_device(), which is always called after enumerating a
PCI device.
Almost all the work here is Huacai's. I restructured it a little bit and
added a few trivial patches on top.
I'd like to move vgaarb.c to drivers/pci eventually, but there's another
initcall ordering snag that needs to be resolved first, so this leaves
it where it is.
Bjorn
Version history:
V0 original implementation as final quirk to set default device.
https://lore.kernel.org/r/20210514080025.1828197-6-chenhuacai@xxxxxxxxxxx
V1 rework vgaarb to do all default device selection in
vga_arbiter_add_pci_device().
https://lore.kernel.org/r/20210705100503.1120643-1-chenhuacai@xxxxxxxxxxx
V2 move arbiter to PCI subsystem, fix nits.
https://lore.kernel.org/r/20210722212920.347118-1-helgaas@xxxxxxxxxx
V3 rewrite the commit log of the last patch (which is also summarized
by Bjorn).
https://lore.kernel.org/r/20210820100832.663931-1-chenhuacai@xxxxxxxxxxx
V4 split the last patch to two steps.
https://lore.kernel.org/r/20210827083129.2781420-1-chenhuacai@xxxxxxxxxxx
V5 split Patch-9 again and sort the patches.
https://lore.kernel.org/r/20210911093056.1555274-1-chenhuacai@xxxxxxxxxxx
V6 split Patch-5 again and sort the patches again.
https://lore.kernel.org/r/20210916082941.3421838-1-chenhuacai@xxxxxxxxxxx
V7 stop moving vgaarb to drivers/pci because of ordering issues with
misc_init().
https://lore.kernel.org/r/20211015061512.2941859-1-chenhuacai@xxxxxxxxxxx
https://lore.kernel.org/r/CAAhV-H7FhAjM-Ha42Z1dLrE4PvC9frfyeU27KHWcyWKkMftEsA@xxxxxxxxxxxxxx
Bjorn Helgaas (8):
vgaarb: Factor out vga_select_framebuffer_device()
vgaarb: Factor out default VGA device selection
vgaarb: Move framebuffer detection to ADD_DEVICE path
vgaarb: Move non-legacy VGA detection to ADD_DEVICE path
vgaarb: Move disabled VGA device detection to ADD_DEVICE path
vgaarb: Remove empty vga_arb_device_card_gone()
vgaarb: Use unsigned format string to print lock counts
vgaarb: Replace full MIT license text with SPDX identifier
Huacai Chen (2):
vgaarb: Move vga_arb_integrated_gpu() earlier in file
vgaarb: Log bridge control messages when adding devices
drivers/gpu/vga/vgaarb.c | 311 +++++++++++++++++++--------------------
1 file changed, 154 insertions(+), 157 deletions(-)
--
2.25.1
