PATCH V1 2026-07-11 08:02:02:
This series modernizes the OpenPandora handheld support by converting the 
sound subsystem and backlight control to proper platform drivers and Device 
Tree definitions.

The primary goal is the complete removal of omap3_pandora_legacy_init() 
and the elimination of the last remaining user of machine_is_omap3_pandora().

History and Context
===================
The necessity of this cleanup was highlighted in several recent discussions:

1. Tony Lindgren noted that machine_is_omap3_pandora() checks never succeed 
   on Device Tree-booted machines, leaving the audio subsystem functionally 
   broken since the DT conversion years ago:
   https://marc.info/?l=alsa-devel&m=165632351319716&w=2

2. Ethan Nelson-Moore submitted a patch to replace the macro with DT 
   compatibility checks (accepted as commit 45efb8fbdae3 in v7.2-rc1):
   https://marc.info/?l=linux-omap&m=177841578110704&w=2

3. Sascha Hauer pointed out that the entire omap3pandora driver fundamentally 
   depended on this broken machine ID check:
   https://marc.info/?l=linux-omap&m=178048982272252&w=2

Design Choices and Implementation
=================================
Based on these discussions and a long-standing and working out-of-tree solution,
we initially attempted a migration to generic frameworks like simple-audio-card 
or audio-graph-card. However, the hardware routing peculiarities of the 
OpenPandora introduced too many functional gaps. Replacing omap3pandora.c 
entirely with pure DT definitions proved unfeasible. 

Therefore, we opted to base a new proposal on the out-of-tree rewrite of
the old-style sound board file kernel driver (sound/soc/ti/omap3pandora.c)
into a proper platform driver that cleanly fetches its resources from the
Device Tree, while adding specific handling for the twl4030-regen output
and adapting the pandora device tree files.

Series Structure
================
* Patches 01–06 (Preparation): Move highly specific legacy code to its proper 
  infrastructure (TWL4030 regulator regeneration and codec handling).
* Patch 07-08 (New Driver): Introduce a dedicated platform driver for the 
  PCM1773 audio DAC.
* Patches 09-14 (Audio Core): Rewrite the omap3pandora ASoC fabric driver 
  and update the respective Device Tree nodes.
* Patches 14–15 (Backlight): Remove the custom, legacy Pandora backlight driver,
  convert it to generic Device Tree nodes
* Patch 16: (Cleanup) safely delete the obsolete omap3_pandora_legacy_init().

Notes & Testing
===============
* Testing: This series has been tested on real OpenPandora hardware.

Credits
=======
This work is a collaborative effort by multiple authors over several years:
* Grond [off-list ref]
* Stefan Leichter [off-list ref]
* H. Nikolaus Schaller [off-list ref]


Grond (8):
  dt-bindings: twl-regulator: Add bindings for exposing ti,twl4030-regen
  regulator: twl: Expose the TWL4030's REGEN signal as a regulator
  arm: dts: twl4030: add twl4030-regen child
  arm: dts: omap3pandora: Populate DT data for the TWL4030's REGEN
    regulator
  arm: dts: omap3pandora: Don't use DMA channels for unused SPI masters
  ASoC: twl4030-codec: Allow setting APLL rate through the .set_sysclk()
    interface
  ASoC: pcm1773-codec: write a driver for the PCM1773 chip from TI
  arm: dts: omap3pandora: Add device node for PCM1773 codec

H. Nikolaus Schaller (5):
  ASoC: dt-bindings: add TI PCM1773
  ASoC: dt-bindings: add OpenPandora Sound Card
  arm: dts: omap3-pandora-common: backlight: switch to twl4030 pwm and
    pwm_bl
  backlight: remove pandora_bl
  arm: omap2: remove remaining pdata-quirks for pandora legacy devices

Stefan Leichter (3):
  ASoC: omap3pandora: Rewrite sound card driver as a platform driver
    with DT
  ARM: dts: omap3-pandora-common: Enable audio in/out (mcbsp4/2)
  arm: dts: omap3pandora: create new DT node for the sound card

 .../devicetree/bindings/mfd/ti,twl.yaml       |   1 +
 .../sound/openpandora,omap3pandora-sound.yaml |  94 ++++
 .../devicetree/bindings/sound/pcm1773.yaml    |  32 ++
 .../dts/ti/omap/omap3-pandora-common.dtsi     |  84 ++++
 arch/arm/boot/dts/ti/omap/twl4030.dtsi        |  14 +
 arch/arm/mach-omap2/pdata-quirks.c            |  23 -
 drivers/regulator/twl-regulator.c             |  52 ++
 drivers/video/backlight/Kconfig               |   7 -
 drivers/video/backlight/Makefile              |   1 -
 drivers/video/backlight/pandora_bl.c          | 159 ------
 include/linux/mfd/twl.h                       |   3 +
 include/linux/mfd/twl4030-audio.h             |   3 +
 sound/soc/codecs/Kconfig                      |   5 +
 sound/soc/codecs/pcm1773.c                    | 149 ++++++
 sound/soc/codecs/twl4030.c                    | 140 ++++--
 sound/soc/ti/omap3pandora.c                   | 454 ++++++++++++------
 16 files changed, 855 insertions(+), 366 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/sound/openpandora,omap3pandora-sound.yaml
 create mode 100644 Documentation/devicetree/bindings/sound/pcm1773.yaml
 delete mode 100644 drivers/video/backlight/pandora_bl.c
 create mode 100644 sound/soc/codecs/pcm1773.c

-- 
2.50.1 (Apple Git-155)