With the help of Gemini 3, a workaound has been found.
Bug Report Summary: Intel Comet Lake cAVS Audio "Cannot Probe Codecs"
Hardware: Intel Comet Lake PCH-LP cAVS OS: Fedora Linux (Kernel 6.x)
Issue: No Analog Audio ("Dummy Output") / Persistent Cannot probe codecs
error on boot.
1. Problem Description
The internal audio codec fails to initialize during the standard boot
sequence. The snd_hda_intel driver loads but fails to detect the codec,
timing out or reporting "Cannot probe."
Modern SOF Path: Fails with IPC Timeout (err: -110) when DSP is
enabled.
Legacy HDA Path: Fails with Cannot probe codecs, giving up.
2. Root Cause Analysis (Diagnosis)
The issue was identified as a resource conflict/race condition between
the Integrated Graphics Audio driver (i915 / snd_hda_codec_hdmi) and the
Legacy Audio driver (snd_hda_intel) during the boot sequence.
Observation: Kernel logs consistently showed the i915 component
binding to the audio controller (bound ... ops
intel_audio_component_bind_ops [i915]) immediately before the
snd_hda_intel driver attempted to probe the codecs.
Failure Mechanism: The HDMI/DP audio component binding appears to
lock the controller or bus state, causing the subsequent probe for the
Realtek analog codec (Address 0) to fail.
Boot Parameter Failure: Standard quirks (probe_mask, position_fix,
model=dell-headset-multi) and even i915.audio=0 failed to prevent this
lock-up during the boot process.
3. Successful Workaround (Runtime "Jailbreak")
A reliable working state could only be achieved by manually breaking the
i915 lock after the system had fully booted.
BIOS Settings:
HD Audio: Enabled
Audio DSP: Enabled (Required for power, but bypassed via software)
Kernel Boot Parameters:
snd_intel_dspcfg.dsp_driver=1 (Forces Legacy HDA driver, bypassing
broken SOF).
snd_hda_intel.power_save=0 (Prevents D3 sleep recursion).
The Fix (Script): The audio functionality is restored only by a delayed
runtime script (systemd service) that performs the following sequence 15
seconds after boot:
Unload Conflict: modprobe -r snd_hda_codec_hdmi followed by modprobe
-r snd_hda_intel.
Hard Bus Reset: Physically cycling the PCI device via sysfs:
Bash
echo 1 > /sys/bus/pci/devices/0000:00:1f.3/remove
sleep 2
echo 1 > /sys/bus/pci/rescan
Clean Reload: modprobe snd_hda_intel model=generic
Conclusion: The hardware is functional, but the current kernel
initialization order allows i915 to monopolize the audio controller
before the legacy probe completes. A delayed, cold re-initialization of
the PCI device clears this state and allows successful probing.
We'll see how it does after a few days.
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https://bugs.launchpad.net/bugs/2130757
Title:
Comet Lake PCH-LP cAVS: Analog audio (Realtek ALCxxx) not detected,
only HDMI outputs present (Dummy Output issue).
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