[PATCH v2 0/3] Properly fix headphone noise on the XPS 13 and other ALC256 devices

[Thomas Hebb]

The root cause of various pervasive audio problems on the XPS 13
9350/9360, mostly relating to the headphone jack, turns out to be an
undocumented feature of the ALC256 and similar codecs that routes audio
along paths not exposed in the HDA node graph. The best we've had so far
to configure this feature is magic numbers provided by Realtek, none of
which have fully fixed all issues.

This series documents the "PC Beep Hidden Register", which controls the
feature and which I've reverse engineered using black box techniques,
and uses my findings to hopefully fix the headphone issues on my XPS 13
once and for all.

Changes in v2:
- Change fixed value from 0x4727 to 0x5757, which should behave
  identically, on advice from Kailang.

Thomas Hebb (3):
  ALSA: doc: Document PC Beep Hidden Register on Realtek ALC256
  ALSA: hda/realtek - Set principled PC Beep configuration for ALC256
  ALSA: hda/realtek - Remove now-unnecessary XPS 13 headphone noise
    fixups

 Documentation/sound/hd-audio/index.rst        |   1 +
 Documentation/sound/hd-audio/models.rst       |   2 -
 .../sound/hd-audio/realtek-pc-beep.rst        | 129 ++++++++++++++++++
 sound/pci/hda/patch_realtek.c                 |  49 ++-----
 4 files changed, 139 insertions(+), 42 deletions(-)
 create mode 100644 Documentation/sound/hd-audio/realtek-pc-beep.rst

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2.25.2