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

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Hi Luke,

On 2024/10/15 4:04 PM, Luke Jones wrote:
On Mon, 14 Oct 2024, at 5:25 PM, Mario Limonciello wrote:
From: Mario Limonciello <mario.limonciello@xxxxxxx>

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@xxxxxxx>
Reported-by: Luke D. Jones <luke@xxxxxxxxxx>
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3673
Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
  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.

Does the following diff work for you?
This variant should be less risky for most systems.

diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c
index 78748e8d2dba..3fb734cb9c1b 100644
--- a/drivers/pci/vgaarb.c
+++ b/drivers/pci/vgaarb.c
@@ -675,6 +675,9 @@ static bool vga_is_boot_device(struct vga_device *vgadev)
                return true;
        }

+       if (vga_arb_integrated_gpu(&pdev->dev))
+               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.


Kai-Heng


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





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