[Nouveau] [RFC, drm-misc-next v4 0/9] PCI/VGA: Allowing the user to select the primary video adapter at boot time

[Thomas Zimmermann]

Hi

Am 04.09.23 um 21:57 schrieb Sui Jingfeng:
> From: Sui Jingfeng <suijingfeng at loongson.cn>
> 
> On a machine with multiple GPUs, a Linux user has no control over which
> one is primary at boot time. This series tries to solve above mentioned

If anything, the primary graphics adapter is the one initialized by the 
firmware. I think our boot-up graphics also make this assumption implicitly.

But what's the use case for overriding this setting?

Best regards
Thomas

> problem by introduced the ->be_primary() function stub. The specific
> device drivers can provide an implementation to hook up with this stub by
> calling the vga_client_register() function.
> 
> Once the driver bound the device successfully, VGAARB will call back to
> the device driver. To query if the device drivers want to be primary or
> not. Device drivers can just pass NULL if have no such needs.
> 
> Please note that:
> 
> 1) The ARM64, Loongarch, Mips servers have a lot PCIe slot, and I would
>     like to mount at least three video cards.
> 
> 2) Typically, those non-86 machines don't have a good UEFI firmware
>     support, which doesn't support select primary GPU as firmware stage.
>     Even on x86, there are old UEFI firmwares which already made undesired
>     decision for you.
> 
> 3) This series is attempt to solve the remain problems at the driver level,
>     while another series[1] of me is target to solve the majority of the
>     problems at device level.
> 
> Tested (limited) on x86 with four video card mounted, Intel UHD Graphics
> 630 is the default boot VGA, successfully override by ast2400 with
> ast.modeset=10 append at the kernel cmd line.
> 
> $ lspci | grep VGA
> 
>   00:02.0 VGA compatible controller: Intel Corporation CoffeeLake-S GT2 [UHD Graphics 630]
>   01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Caicos XTX [Radeon HD 8490 / R5 235X OEM]
>   04:00.0 VGA compatible controller: ASPEED Technology, Inc. ASPEED Graphics Family (rev 30)
>   05:00.0 VGA compatible controller: NVIDIA Corporation GK208B [GeForce GT 720] (rev a1)
> 
> $ sudo dmesg | grep vgaarb
> 
>   pci 0000:00:02.0: vgaarb: setting as boot VGA device
>   pci 0000:00:02.0: vgaarb: VGA device added: decodes=io+mem,owns=io+mem,locks=none
>   pci 0000:01:00.0: vgaarb: VGA device added: decodes=io+mem,owns=none,locks=none
>   pci 0000:04:00.0: vgaarb: VGA device added: decodes=io+mem,owns=none,locks=none
>   pci 0000:05:00.0: vgaarb: VGA device added: decodes=io+mem,owns=none,locks=none
>   vgaarb: loaded
>   ast 0000:04:00.0: vgaarb: Override as primary by driver
>   i915 0000:00:02.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=none:owns=io+mem
>   radeon 0000:01:00.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=none:owns=none
>   ast 0000:04:00.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=none:owns=none
> 
> v2:
> 	* Add a simple implemment for drm/i915 and drm/ast
> 	* Pick up all tags (Mario)
> v3:
> 	* Fix a mistake for drm/i915 implement
> 	* Fix patch can not be applied problem because of merge conflect.
> v4:
> 	* Focus on solve the real problem.
> 
> v1,v2 at https://patchwork.freedesktop.org/series/120059/
>     v3 at https://patchwork.freedesktop.org/series/120562/
> 
> [1] https://patchwork.freedesktop.org/series/122845/
> 
> Sui Jingfeng (9):
>    PCI/VGA: Allowing the user to select the primary video adapter at boot
>      time
>    drm/nouveau: Implement .be_primary() callback
>    drm/radeon: Implement .be_primary() callback
>    drm/amdgpu: Implement .be_primary() callback
>    drm/i915: Implement .be_primary() callback
>    drm/loongson: Implement .be_primary() callback
>    drm/ast: Register as a VGA client by calling vga_client_register()
>    drm/hibmc: Register as a VGA client by calling vga_client_register()
>    drm/gma500: Register as a VGA client by calling vga_client_register()
> 
>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c    | 11 +++-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c       | 13 ++++-
>   drivers/gpu/drm/ast/ast_drv.c                 | 31 ++++++++++
>   drivers/gpu/drm/gma500/psb_drv.c              | 57 ++++++++++++++++++-
>   .../gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c   | 15 +++++
>   drivers/gpu/drm/i915/display/intel_vga.c      | 15 ++++-
>   drivers/gpu/drm/loongson/loongson_module.c    |  2 +-
>   drivers/gpu/drm/loongson/loongson_module.h    |  1 +
>   drivers/gpu/drm/loongson/lsdc_drv.c           | 10 +++-
>   drivers/gpu/drm/nouveau/nouveau_vga.c         | 11 +++-
>   drivers/gpu/drm/radeon/radeon_device.c        | 10 +++-
>   drivers/pci/vgaarb.c                          | 43 ++++++++++++--
>   drivers/vfio/pci/vfio_pci_core.c              |  2 +-
>   include/linux/vgaarb.h                        |  8 ++-
>   14 files changed, 210 insertions(+), 19 deletions(-)
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
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