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

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Message-ID: <20251012184717.GB3412@sol>
Date: Sun, 12 Oct 2025 11:47:17 -0700
From: Eric Biggers <ebiggers@...nel.org>
To: Mario Limonciello <superm1@...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 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.

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

- Eric