Public bug reported:
I am sorry if the information is too generic, the description below is
ai-generated and it's a recap of the problem i faced and the steps i did
to fix an issue with the external monitors not being detected, i thought
it would be helpful if you want to address this issue.
External monitors are no longer detected when booting Ubuntu 24.04 with
kernel 7.0.0-34-generic.
The same hardware and configuration works correctly when booting the
previous installed kernel 7.0.0-31-generic.
This appears to be an i915 DisplayPort/Type-C regression introduced
between these kernel versions.
Hardware
The system has:
Intel Alder Lake-P GT2 / Iris Xe Graphics
NVIDIA GeForce RTX 3060 Mobile / Max-Q
Dell laptop
Ubuntu 24.04
Wayland
PCI devices:
00:02.0 VGA compatible controller: Intel Corporation Alder Lake-P GT2 [Iris Xe
Graphics] (rev 0c)
01:00.0 VGA compatible controller: NVIDIA Corporation GA106M [GeForce RTX 3060
Mobile / Max-Q] (rev a1)
Reproduction
Boot Ubuntu with kernel 7.0.0-34-generic.
Connect external monitors through the laptop's external display outputs.
External monitors are not detected.
/sys/class/drm reports the internal display as connected, but external
connectors as disconnected.
Relevant output:
/sys/class/drm/card1-DP-1/status: disconnected
/sys/class/drm/card1-DP-2/status: disconnected
/sys/class/drm/card1-eDP-1/status: connected
/sys/class/drm/card1-HDMI-A-1/status: disconnected
The kernel log repeatedly reports the following i915 warning while
probing the display connectors:
i915 0000:00:02.0: [drm] drm_WARN_ON(tc->mode == TC_PORT_LEGACY)
WARNING: drivers/gpu/drm/i915/display/intel_tc.c:934 at
adlp_tc_phy_connect+0x1a3/0x260 [i915]
The relevant call path includes:
intel_tc_port_reset_mode
__intel_tc_port_lock
intel_tc_port_lock
intel_digital_port_connected
intel_dp_detect
drm_helper_probe_single_connector_modes
The warning occurs repeatedly during boot/KMS connector probing.
Kernel comparison
The same system works correctly when booted with:
7.0.0-31-generic
External monitors are detected and usable with that kernel.
With:
7.0.0-34-generic
the external monitors are not detected.
No hardware or cabling changes were made between the tests.
Additional information
The issue persists after a normal reboot.
The installed HWE package reports:
linux-generic-hwe-24.04:
Installed: 7.0.0-34.34~24.04.1
Candidate: 7.0.0-34.34~24.04.1
The older kernel remains installed:
linux-image-7.0.0-31-generic
linux-image-7.0.0-34-generic
At the time of reporting, the configured Ubuntu repositories do not
offer a newer HWE kernel.
Expected behavior
External DisplayPort/HDMI monitors should be detected and available with
kernel 7.0.0-34-generic, as they are with 7.0.0-31-generic.
Actual behavior
Only the internal eDP display is detected. External DP/HDMI connectors
remain reported as disconnected.
The i915 driver repeatedly reports:
drm_WARN_ON(tc->mode == TC_PORT_LEGACY)
during Type-C/DisplayPort connector detection.
Workaround
Booting the previous kernel:
7.0.0-31-generic
restores external monitor functionality.
Assessment
I cannot determine whether this is specifically a kernel regression in
7.0.0-34 or an interaction between this kernel and the laptop's
firmware/hardware implementation, but the reproducible difference
between 7.0.0-31 and 7.0.0-34, together with the i915
adlp_tc_phy_connect() warnings, strongly suggests an Intel display
driver/kernel regression.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Description changed:
+ I am sorry if the information is too generic, the description below is
+ ai-generated and it's a recap of the problem i faced and the steps i did
+ to fix an issue with the external monitors not being detected, i thought
+ it would be helpful if you want to address this issue.
+
External monitors are no longer detected when booting Ubuntu 24.04 with
kernel 7.0.0-34-generic.
The same hardware and configuration works correctly when booting the
previous installed kernel 7.0.0-31-generic.
This appears to be an i915 DisplayPort/Type-C regression introduced
between these kernel versions.
Hardware
The system has:
Intel Alder Lake-P GT2 / Iris Xe Graphics
NVIDIA GeForce RTX 3060 Mobile / Max-Q
Dell laptop
Ubuntu 24.04
Wayland
PCI devices:
00:02.0 VGA compatible controller: Intel Corporation Alder Lake-P GT2 [Iris
Xe Graphics] (rev 0c)
01:00.0 VGA compatible controller: NVIDIA Corporation GA106M [GeForce RTX
3060 Mobile / Max-Q] (rev a1)
Reproduction
Boot Ubuntu with kernel 7.0.0-34-generic.
Connect external monitors through the laptop's external display outputs.
External monitors are not detected.
/sys/class/drm reports the internal display as connected, but external
connectors as disconnected.
Relevant output:
/sys/class/drm/card1-DP-1/status: disconnected
/sys/class/drm/card1-DP-2/status: disconnected
/sys/class/drm/card1-eDP-1/status: connected
/sys/class/drm/card1-HDMI-A-1/status: disconnected
The kernel log repeatedly reports the following i915 warning while
probing the display connectors:
i915 0000:00:02.0: [drm] drm_WARN_ON(tc->mode == TC_PORT_LEGACY)
WARNING: drivers/gpu/drm/i915/display/intel_tc.c:934 at
adlp_tc_phy_connect+0x1a3/0x260 [i915]
The relevant call path includes:
intel_tc_port_reset_mode
__intel_tc_port_lock
intel_tc_port_lock
intel_digital_port_connected
intel_dp_detect
drm_helper_probe_single_connector_modes
The warning occurs repeatedly during boot/KMS connector probing.
Kernel comparison
The same system works correctly when booted with:
7.0.0-31-generic
External monitors are detected and usable with that kernel.
With:
7.0.0-34-generic
the external monitors are not detected.
No hardware or cabling changes were made between the tests.
Additional information
The issue persists after a normal reboot.
The installed HWE package reports:
linux-generic-hwe-24.04:
- Installed: 7.0.0-34.34~24.04.1
- Candidate: 7.0.0-34.34~24.04.1
+ Installed: 7.0.0-34.34~24.04.1
+ Candidate: 7.0.0-34.34~24.04.1
The older kernel remains installed:
linux-image-7.0.0-31-generic
linux-image-7.0.0-34-generic
At the time of reporting, the configured Ubuntu repositories do not
offer a newer HWE kernel.
Expected behavior
External DisplayPort/HDMI monitors should be detected and available with
kernel 7.0.0-34-generic, as they are with 7.0.0-31-generic.
Actual behavior
Only the internal eDP display is detected. External DP/HDMI connectors
remain reported as disconnected.
The i915 driver repeatedly reports:
drm_WARN_ON(tc->mode == TC_PORT_LEGACY)
during Type-C/DisplayPort connector detection.
Workaround
Booting the previous kernel:
7.0.0-31-generic
restores external monitor functionality.
Assessment
I cannot determine whether this is specifically a kernel regression in
7.0.0-34 or an interaction between this kernel and the laptop's
firmware/hardware implementation, but the reproducible difference
between 7.0.0-31 and 7.0.0-34, together with the i915
adlp_tc_phy_connect() warnings, strongly suggests an Intel display
driver/kernel regression.
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https://bugs.launchpad.net/bugs/2169109
Title:
External DisplayPort/HDMI outputs stop working with kernel 7.0.0-34 on
Intel Alder Lake / Iris Xe
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