linux-kernel - [PATCH v9 00/11] vgaarb: Rework default VGA device selection

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Date:   Thu, 24 Feb 2022 16:47:42 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Huacai Chen <chenhuacai@...ngson.cn>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: [PATCH v9 00/11] vgaarb: Rework default VGA device selection

From: Bjorn Helgaas <bhelgaas@...gle.com>

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.

The big change from the v8 posting is that this moves vgaarb.c from
drivers/gpu/vga to drivers/pci because it really has nothing to do with
GPUs or DRM.

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.

Bjorn

Version history:
V0 original implementation as final quirk to set default device.
https://lore.kernel.org/r/20210514080025.1828197-6-chenhuacai@loongson.cn

V1 rework vgaarb to do all default device selection in
vga_arbiter_add_pci_device().
https://lore.kernel.org/r/20210705100503.1120643-1-chenhuacai@loongson.cn

V2 move arbiter to PCI subsystem, fix nits.
https://lore.kernel.org/r/20210722212920.347118-1-helgaas@kernel.org

V3 rewrite the commit log of the last patch (which is also summarized
by Bjorn).
https://lore.kernel.org/r/20210820100832.663931-1-chenhuacai@loongson.cn

V4 split the last patch to two steps.
https://lore.kernel.org/r/20210827083129.2781420-1-chenhuacai@loongson.cn

V5 split Patch-9 again and sort the patches.
https://lore.kernel.org/r/20210911093056.1555274-1-chenhuacai@loongson.cn

V6 split Patch-5 again and sort the patches again.
https://lore.kernel.org/r/20210916082941.3421838-1-chenhuacai@loongson.cn

V7 stop moving vgaarb to drivers/pci because of ordering issues with
misc_init().
https://lore.kernel.org/r/20211015061512.2941859-1-chenhuacai@loongson.cn
https://lore.kernel.org/r/CAAhV-H7FhAjM-Ha42Z1dLrE4PvC9frfyeU27KHWcyWKkMftEsA@mail.gmail.com

V8 expand commit logs, rework boot VGA device selection
https://lore.kernel.org/r/20220106000658.243509-1-helgaas@kernel.org

V9 (this posting) move to drivers/pci, resolve initcall ordering, rename
vga_is_framebuffer_device() to vga_is_firmware_default()

Bjorn Helgaas (5):
  PCI/VGA: Move vgaarb to drivers/pci
  PCI/VGA: Factor out vga_select_framebuffer_device()
  PCI/VGA: Remove empty vga_arb_device_card_gone()
  PCI/VGA: Use unsigned format string to print lock counts
  PCI/VGA: Replace full MIT license text with SPDX identifier

Huacai Chen (6):
  PCI/VGA: Move vga_arb_integrated_gpu() earlier in file
  PCI/VGA: Factor out default VGA device selection
  PCI/VGA: Move firmware default device detection to ADD_DEVICE path
  PCI/VGA: Move non-legacy VGA detection to ADD_DEVICE path
  PCI/VGA: Move disabled VGA device detection to ADD_DEVICE path
  PCI/VGA: Log bridge control messages when adding devices

 drivers/gpu/vga/Kconfig           |  19 --
 drivers/gpu/vga/Makefile          |   1 -
 drivers/pci/Kconfig               |  19 ++
 drivers/pci/Makefile              |   1 +
 drivers/{gpu/vga => pci}/vgaarb.c | 313 +++++++++++++++---------------
 5 files changed, 175 insertions(+), 178 deletions(-)
 rename drivers/{gpu/vga => pci}/vgaarb.c (90%)

-- 
2.25.1