On Thu, Jul 17, 2025 at 12:38:03PM -0500, Mario Limonciello wrote: > From: Mario Limonciello <mario.limoncie...@amd.com> > > Systems with more than one GPU userspace doesn't know which one to be > used to treat as primary. The concept of primary is important to be > able to decide which GPU is used for display and which is used for > rendering. If it's guessed wrong then both GPUs will be kept awake > burning a lot of power. > > Historically it would use the "boot_vga" attribute but this isn't > present on modern GPUs. > > This series started out as changes to VGA arbiter to try to handle a case > of a system with 2 GPUs that are not VGA devices and avoid changes to > userspace. This was discussed but decided not to overload the VGA arbiter > for non VGA devices. > > Instead move the x86 specific detection of framebuffer resources into x86 > specific code that the fbcon can use to properly identify the primary > device. This code is still called from the VGA arbiter, and the logic does > not change there. To avoid regression default to VGA arbiter and only fall > back to looking up with x86 specific detection method. > > In order for userspace to also be able to discover which device was the > primary video display device create a new sysfs file 'boot_display'. > > A matching userspace implementation for this file is available here: > Link: https://gitlab.freedesktop.org/xorg/lib/libpciaccess/-/merge_requests/39 > Link: https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2038 > > Dave Airlie has been pinged for a comment on this approach. > Dave had suggested in the past [1]: > > " > But yes if that doesn't work, then maybe we need to make the boot_vga > flag mean boot_display_gpu, and fix it in the kernel > " > > This was one of the approached tried in earlier revisions and it was > rejected in favor of creating a new sysfs file (which is what this > version does). > > It is suggested that this series merge entirely through the PCI tree. > > Link: > https://gitlab.freedesktop.org/xorg/lib/libpciaccess/-/merge_requests/37#note_2938602 > [1] > > v9: > * Add more to cover letter > * Add bug link to last patch > * Update commit message for last patch > * Update boot_display documentation description > > Mario Limonciello (9): > PCI: Add helper for checking if a PCI device is a display controller > vfio/pci: Use pci_is_display() > vga_switcheroo: Use pci_is_display() > iommu/vt-d: Use pci_is_display() > ALSA: hda: Use pci_is_display() > Fix access to video_is_primary_device() when compiled without > CONFIG_VIDEO > PCI/VGA: Replace vga_is_firmware_default() with a screen info check > fbcon: Use screen info to find primary device > PCI: Add a new 'boot_display' attribute > > Documentation/ABI/testing/sysfs-bus-pci | 9 +++++ > arch/parisc/include/asm/video.h | 2 +- > arch/sparc/include/asm/video.h | 2 ++ > arch/x86/include/asm/video.h | 2 ++ > arch/x86/video/video-common.c | 17 ++++++++- > drivers/gpu/vga/vga_switcheroo.c | 2 +- > drivers/iommu/intel/iommu.c | 2 +- > drivers/pci/pci-sysfs.c | 46 +++++++++++++++++++++++++ > drivers/pci/vgaarb.c | 31 +++-------------- > drivers/vfio/pci/vfio_pci_igd.c | 3 +- > include/linux/pci.h | 15 ++++++++ > sound/hda/hdac_i915.c | 2 +- > sound/pci/hda/hda_intel.c | 4 +-- > 13 files changed, 102 insertions(+), 35 deletions(-)
Applied to pci/boot-display for v6.17, thanks!
