# linux-omarchy 7.2.5 kernel causes constant HDMI audio underruns (distortion/clipping) on Haswell Mac — stock Arch linux 7.2.3 works

## What happened

After the 2026-09-16 update (Omarchy 4.0.4), which installed the new `linux-omarchy 7.2.5-3` kernel package and made it the default boot entry (`BOOT_ORDER="linux-omarchy, ..."` in `/etc/default/limine`), audio played to an HDMI display (LG TV) is heavily distorted and clipping.

PipeWire's journal floods with ALSA underruns on the HDMI device while playing:

```
Sep 16 17:29:32 macomarchy pipewire[773]: spa.alsa: hdmi:0p: (0 suppressed) snd_pcm_avail after recover: Broken pipe
Sep 16 17:29:35 macomarchy pipewire[773]: spa.alsa: hdmi:0p: (2 suppressed) snd_pcm_avail after recover: Broken pipe
Sep 16 17:29:37 macomarchy pipewire[773]: spa.alsa: hdmi:0p: (4 suppressed) snd_pcm_avail after recover: Broken pipe
...continuing ~10 messages per 20 seconds of playback
```

`pw-top` shows the HDMI sink's ERR counter climbing ~7–8/second during playback (1311 → 1358 within seconds). Moving a Bluetooth mouse makes the distortion audibly worse (interrupt load). Bluetooth A2DP output and the analog output are unaffected.

## What I ruled out (not userspace)

- RT scheduling is working: rtkit grants RR priority 20, `data-loop.0` threads confirmed RR via `ps -eLo`.
- Forcing a larger buffer does not help: `pw-metadata -n settings 0 clock.force-quantum 2048` (21ms → 43ms) left the underrun rate unchanged (~11 errors/20s). So this is not scheduling starvation — the ALSA device itself is failing.
- No user config overrides: no `~/.config/pipewire`, `/etc/pipewire/pipewire.conf.d` empty; WirePlumber config only has a Bluetooth A2DP autoconnect rule.

## A/B proof (same userspace both times: PipeWire 1.6.8, WirePlumber 0.5.17)

| Boot | Kernel | Broken-pipe messages during HDMI playback |
|------|--------|-------------------------------------------|
| multiple | `7.2.5-3-omarchy` (linux-omarchy) | constant, distortion heard |
| manual Limine selection | `7.2.3-arch1-3` (stock Arch `linux`) | **zero — audio perfect**, also while moving the BT mouse |

The stock Arch `linux 7.2.3-arch1-3` package was still installed; selecting it from the Limine menu (`/+Omarchy` → `Kernel version: 7.2.3-arch1-3`) fixes audio completely. Reverting to the omarchy kernel reproduces the problem immediately. This points to either upstream 7.2.4/7.2.5 changes (HDA/i915) or a `linux-omarchy` config delta (e.g. it builds with `CONFIG_NO_HZ_FULL=y` and `CONFIG_SCHED_CLASS_EXT=y`).

## Steps to reproduce

1. System on linux-omarchy 7.2.5-3 (Omarchy 4.0.4, updated 2026-09-16).
2. Play any audio to an HDMI sink (Intel Crystal Well HDA, `snd_hda_intel`, audio device `00:03.0 Intel Crystal Well HD Audio Controller`).
3. Observe distortion; `journalctl --user -u pipewire -f` shows the `snd_pcm_avail after recover: Broken pipe` flood on `hdmi:0p`.
4. Reboot into the stock Arch `linux` kernel via the Limine menu → problem gone.

## System details

- Omarchy 4.0.4-1, kernel `7.2.5-3-omarchy` (regressed) / `7.2.3-arch1-3` (working)
- MacBookPro11,2 (Retina, Late 2013), Intel Core i7-4770HQ, Crystal Well integrated graphics
- Audio: `snd_hda_intel`, two HDA devices (`00:03.0` Crystal Well HDMI → LG TV, `00:1b.0` 8 Series/C220 PCH)
- PipeWire 1.6.8, WirePlumber 0.5.17, rtkit 0.14
- HDMI sink runs S32LE 2ch 48000Hz, quantum 1024 (default)

## Current workaround

Removed `linux-omarchy` and `linux-omarchy-headers`, booting the stock `linux` kernel. Note: if the root cause is an upstream 7.2.4+ regression rather than the omarchy config, future stock `linux` package updates may carry it too — happy to help bisect (e.g. test stock 7.2.4/7.2.6 when available, or diff kernel configs).