Re: [resend] [regression] amdgpu carrizo: no display signal after modeset

[Salvatore Bonaccorso <carnil@debian.org>]

Hi

Resending because of typ in mailing list address.

On Sat, Jun 20, 2026 at 10:11:25PM +0200, Salvatore Bonaccorso wrote:
> Control: forwarded -1 https://lore.kernel.org/regressions/178198613176.3658222.16247101620976737948@eldamar.lan
> 
> Hi
> 
> Jaak Ristioja reported the following issue in Debian at
> https://bugs.debian.org/1139950 . Part of the original report contains
> Debian specific version information, but Jaak did as well a bisecion
> for the regression see below:
> 
> On Sun, Jun 14, 2026 at 02:27:01AM +0300, Jaak Ristioja wrote:
> > Package: linux-modules-7.0.10+deb13-amd64
> > Version: 7.0.10-1~bpo13+1
> > 
> > Hi,
> > 
> > Upgrading (after a long while) Debian Trixie installations on two different
> > HP EliteDesk 705 G4 DM 35W computers with AMD PRO A10-9700E R7 (carrizo)
> > resulted in both machines blanking the screen right after kernel modesetting
> > activates via amdgpu, with the monitor reporting "no signal". There are no
> > other symptoms besides losing the display as the system continues to run and
> > is accessible using keyboard and network.
> > 
> > Bug first discovered with stable kernel linux-image-6.12.90+deb13.1-amd64
> > (6.12.90-2) and the one from trixie-backports. The device is connected to a
> > monitor using a DisplayPort to HDMI adapter. The bug occurs regardless of
> > which if the two available physical DisplayPort ports to use.
> > 
> > I don't remember this being an issue some months ago, so I tried to
> > reproduce this booting the Debian 13.1.0 and 13.4.0 install DVD images and
> > using the kernel modules/firmware therein:
> > 
> >   13.1.0 installer:
> >     firmware-amd-graphics_20250410-2
> >     linux-image-6.12.43+deb13-amd64_6.12.43-1
> >   13.4.0 installer:
> >     firmware-amd-graphics 20250410-2
> >     linux-image-6.12.73+deb13-amd64_6.12.73-1
> > 
> > I essentially unpacked the two *.deb files manually, depmod -a; modprobe drm
> > debug=0x1ff; modprobe amdgpu.
> > 
> > I observed the bug reproduce using the 13.4.0 installer, but not on the
> > 13.1.0 installer, meaning this is a regression somewhere between kernel
> > versions 6.12.43-1 and 6.12.73-1.
> 
> The reporter did a bisection and found as offending commit:
> 
>     drm/amd/display: Bump the HDMI clock to 340MHz
> 
>     commit fee50077656d8a58011f13bca48f743d1b6d6015 upstream.
> 
>     [Why]
>     DP-HDMI dongles can execeed bandwidth requirements on high resolution
>     monitors. This can lead to pruning the high resolution modes.
> 
>     HDMI 1.3 bumped the clock to 340MHz, but display code never matched it.
> 
>     [How]
>     Set default to (DVI) 165MHz.  Once HDMI display is identified update
>     to 340MHz.
> 
>     Reported-by: Dianne Skoll <dianne@skoll.ca>
>     Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4780
>     Reviewed-by: Chris Park <chris.park@amd.com>
>     Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>     Signed-off-by: Matthew Stewart <matthew.stewart2@amd.com>
>     Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
>     Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
>     (cherry picked from commit ac1e65d8ade46c09fb184579b81acadf36dcb91e)
>     Cc: stable@vger.kernel.org
>     Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> Does this ring any bell?
> 
> #regzbot introduced: ae5b1d291c814a2884c3d54a56e83bc99052b1eb
> #regzbot link: https://bugs.debian.org/1139950
> 
> Regards,
> Salvatore