linux-kernel - Re: [PATCH] PCI/VGA: Don't assume only VGA device found is the boot VGA device

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Message-Id: <20b48c6f-7ea9-4571-a39c-f20a9cf62319@app.fastmail.com>
Date: Tue, 15 Oct 2024 10:04:47 +0200
From: "Luke Jones" <luke@...nes.dev>
To: "Mario Limonciello" <superm1@...nel.org>,
 "Bjorn Helgaas" <bhelgaas@...gle.com>
Cc: "open list:PCI SUBSYSTEM" <linux-pci@...r.kernel.org>,
 "open list" <linux-kernel@...r.kernel.org>, dri-devel@...ts.freedesktop.org,
 "Mario Limonciello" <mario.limonciello@....com>,
 "Alex Deucher" <alexander.deucher@....com>
Subject: Re: [PATCH] PCI/VGA: Don't assume only VGA device found is the boot VGA device

On Mon, 14 Oct 2024, at 5:25 PM, Mario Limonciello wrote:
> From: Mario Limonciello <mario.limonciello@....com>
>
> The ASUS GA605W has a NVIDIA PCI VGA device and an AMD PCI display device.
>
> ```
> 65:00.0 VGA compatible controller: NVIDIA Corporation AD106M [GeForce 
> RTX 4070 Max-Q / Mobile] (rev a1)
> 66:00.0 Display controller: Advanced Micro Devices, Inc. [AMD/ATI] 
> Strix [Radeon 880M / 890M] (rev c1)
> ```
>
> The fallback logic in vga_is_boot_device() flags the NVIDIA dGPU as the
> boot VGA device, but really the eDP is connected to the AMD PCI display
> device.
>
> Drop this case to avoid marking the NVIDIA dGPU as the boot VGA device.
>
> Suggested-by: Alex Deucher <alexander.deucher@....com>
> Reported-by: Luke D. Jones <luke@...nes.dev>
> Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3673
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
>  drivers/pci/vgaarb.c | 7 -------
>  1 file changed, 7 deletions(-)
>
> diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c
> index 78748e8d2dba..05ac2b672d4b 100644
> --- a/drivers/pci/vgaarb.c
> +++ b/drivers/pci/vgaarb.c
> @@ -675,13 +675,6 @@ static bool vga_is_boot_device(struct vga_device *vgadev)
>  		return true;
>  	}
> 
> -	/*
> -	 * Vgadev has neither IO nor MEM enabled.  If we haven't found any
> -	 * other VGA devices, it is the best candidate so far.
> -	 */
> -	if (!boot_vga)
> -		return true;
> -
>  	return false;
>  }
> 
> -- 
> 2.43.0

Hi Mario,

I can verify that this does leave the `boot_vga` attribute set as 0 for the NVIDIA device.

Tested-by: Luke D. Jones <luke@...nes.dev>