linux-kernel - Re: [PATCH v10 2/4] PCI/VGA: Replace vga_is_firmware

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Message-ID: <65c24236-044c-4b65-baaa-dc0011ea69d8@kernel.org>
Date: Sun, 12 Oct 2025 14:06:56 -0500
From: Mario Limonciello <superm1@...nel.org>
To: Eric Biggers <ebiggers@...nel.org>
Cc: David Airlie <airlied@...il.com>, Bjorn Helgaas <bhelgaas@...gle.com>,
 Alex Deucher <alexander.deucher@....com>,
 Christian König <christian.koenig@....com>,
 Simona Vetter <simona@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
 open list <linux-kernel@...r.kernel.org>,
 "open list:PCI SUBSYSTEM" <linux-pci@...r.kernel.org>,
 Daniel Dadap <ddadap@...dia.com>
Subject: Re: [PATCH v10 2/4] PCI/VGA: Replace vga_is_firmware_default() with a
 screen info check



On 10/12/25 1:47 PM, Eric Biggers wrote:
> On Sun, Oct 12, 2025 at 01:37:33PM -0500, Mario Limonciello wrote:
>>
>>
>> On 10/12/25 1:23 PM, Eric Biggers wrote:
>>> Hi,
>>>
>>> On Mon, Aug 11, 2025 at 11:26:04AM -0500, Mario Limonciello (AMD) wrote:
>>>> vga_is_firmware_default() checks firmware resources to find the owner
>>>> framebuffer resources to find the firmware PCI device.  This is an
>>>> open coded implementation of screen_info_pci_dev().  Switch to using
>>>> screen_info_pci_dev() instead.
>>>>
>>>> Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
>>>> Suggested-by: Thomas Zimmermann <tzimmermann@...e.de>
>>>> Signed-off-by: Mario Limonciello (AMD) <superm1@...nel.org>
>>>
>>> I'm getting a black screen on boot on mainline, and it bisected to this
>>> commit.  Reverting this commit fixed it.
>>>
>>> Please revert.
>>>
>>> - Eric
>>
>> Can you please share more information about your issue before we jump
>> straight into a revert?  What kind of hardware do you have?  Perhaps a
>> kernel log from mainline and another from mainline with the revert could
>> help identify what's going on?
>>
>> A revert might be the right solution, but I would rather fix the issue if
>> it's plausible to do so.
> 
> Relevant hardware is:
>      AMD Ryzen 9 9950X 16-Core Processor
>      Radeon RX 9070
> 
> The following message appears in the good log but not the bad log:
> 
>      fbcon: amdgpudrmfb (fb0) is primary device
> 
> I don't have CONFIG_SCREEN_INFO enabled, so the commit changed
> vga_is_firmware_default() to always return false.

Thanks, that definitely explains it.

> 
> If DRM_AMDGPU depends on SCREEN_INFO now, it needs to select it.
> 
> - Eric

Well the question now is which driver should actually select it.

Although it manifested for you in amdgpu, I don't think this is going to 
be an amdgpu unique issue.

Maybe this:

diff --git a/drivers/video/fbdev/core/Kconfig 
b/drivers/video/fbdev/core/Kconfig
index 006638eefa41..ce2544924b0e 100644
--- a/drivers/video/fbdev/core/Kconfig
+++ b/drivers/video/fbdev/core/Kconfig
@@ -5,6 +5,7 @@

  config FB_CORE
         select VIDEO
+       select SCREEN_INFO
         tristate

  config FB_NOTIFY