When I reboot, I often see something akin to:
amdgpu0000:59:00.0: [drm] *ERROR*lttpr_capsphy_repeater_cntis0x0, forcing it to0x80
Has anyone else seen it? Do you know why it’s repeatedly posted to the TTY in boot-dmesg mode?
I ask because checking the boot log for repetitions has already allowed me to report gitlab.freedesktop.org/drm/amd/-/issues/3248, so I’d like to ascertain whether it’s expected, in order to reduce the superfluous logs further.
This persists across an OS reinstallation.
Consequently, I’ve reported it (albeit upstream, hopefully not erroneously):
A competent explanation from an OpenAI LLM (presumably GPT4.0) states:
amdgpu 0000:59:00.0: [drm] *ERROR* lttpr_caps phy_repeater_cnt is 0x0, forcing it to 0x80.Component
This relates to LTTPR (Link Training Tunable PHY Repeater), part of DisplayPort 1.4+ spec.
Cause
The GPU queries the capabilities of the DisplayPort link (via DPCD registers) and finds the repeater count (
phy_repeater_cnt) to be 0x0, which is invalid or unexpected.Effect
The driver forcibly sets it to
0x80, a default value (meaning one repeater with one segment).Implication
This typically indicates a problem in DisplayPort signal negotiation, DP-to-HDMI adapters, hubs, or cables.
amdgpu 0000:59:00.0: [drm] Cannot find any crtc or sizesComponent
CRTC = Cathode Ray Tube Controller, a part of the kernel’s DRM/KMS display pipeline.
Cause
The GPU is trying to assign a display to a CRTC but can’t find a compatible one. This usually happens when:
No display is detected or connected.
There’s a miscommunication between the GPU and the display hardware (especially via DisplayPort).
Something is polling for a new display repeatedly and failing.