[PATCH v4 0/4] ASoC: qcom: enable audio on stage-2 protected DSPs (mDSP)

[Ajay Kumar Nandam]

On platforms such as Qualcomm Shikra, audio is served by the modem DSP
(mDSP) rather than the ADSP. The mDSP runs in a stage-2 protected context
and cannot use the SMMU, so the PCM buffers it consumes must live in
reserved-memory carveouts that are handed to the consumer VMIDs via a
hypervisor (SCM) memory assignment. This series adds that access model to
the q6apm DAI driver and its binding, alongside the existing stage-1/SMMU
(iommus) path, which is left untouched.

The driver detects the mDSP target at runtime from the GPR domain_id
(GPR_DOMAIN_ID_MODEM) and enables the SCM assignment path automatically.
VMIDs are hardcoded in the driver (HLOS + MSS_MSA + LPASS) rather than
read from DT, following the consensus from v2 review discussion with
Krzysztof Kozlowski and Srinivas Kandagatla.

Tested on Qualcomm Shikra with mDSP audio playback and capture.

Prior versions:
v1 (VMID binding + driver + GPR domain):
  https://lore.kernel.org/all/20260609064038.492641-1-ajay.nandam@xxxxxxxxxxxxxxxx/
v1 (memory-region binding + DTS):
  https://lore.kernel.org/all/20260618113509.2025881-1-ajay.nandam@xxxxxxxxxxxxxxxx/
v2:
  https://lore.kernel.org/all/20260826-a2a-shikra-vmid-v5-v2-0-c3dc62354eee@xxxxxxxxxxxxxxxx/
v3:
  https://lore.kernel.org/all/20260918-vmid-v3-v3-0-f1cbf47bf173@xxxxxxxxxxxxxxxx/

Changes since v3:
- Split DT binding changes into a separate patch (3/4) from the driver
  implementation (4/4). (Rob Herring)
- SCM-assign the data-path pool (memory-region[1]) as a single whole-pool
  operation at probe instead of per-stream in pcm_new()/compr_open().
- SCM-assign compressed audio stream buffers in compr_open() and
  unassign in compr_free() when no data-path pool is present. v3 only
  covered PCM streams.
- Fix error path in pcm_new: unassign SCM region if memory_map fails
  after a successful SCM assign, preventing a resource leak.
- Account for PAGE_SIZE padding in reserved-memory pool budget
  calculation. v3 under-reserved by PAGE_SIZE per stream, which could
  overflow the pool at maximum concurrent stream count.

Changes since v2:
- Drop qcom,vmids DT property entirely; VMIDs are static per SoC and
  hardcoded in the driver (HLOS, MSS_MSA, LPASS). This addresses
  Krzysztof's concern that qcom,vmids is "not a hardware property at
  all" and does not belong in DT. (Krzysztof Kozlowski)
- Drop oneOf / dependentRequired constraints from the binding since
  qcom,vmids no longer exists. memory-region is simply optional.
- Detect mDSP from GPR domain_id (GPR_DOMAIN_ID_MODEM) instead of
  keying off a DT property. No new compatible needed.
- Add QCOM_SCM_VMID_LPASS to the SCM destination list alongside
  HLOS and MSS_MSA — required for the mDSP firmware to access
  buffers.
- Switch reserved-memory path from snd_pcm_set_managed_buffer_all()
  to snd_pcm_set_fixed_buffer_all() so the carveout is not subject
  to the preallocate_dma module param. (Mark Brown)
- Use per-item descriptions for memory-region in the DT binding
  instead of free-form text. (Krzysztof Kozlowski)
- Drop reserved-memory node from the binding example.
  (Krzysztof Kozlowski)
- Register devm cleanup action before SCM assigns so probe-error
  paths do not leak HLOS memory access.
- Reorder series: g_apm fix (1/4), GPR domain (2/4), DT binding
  (3/4), SCM assign (4/4) for cleaner bisection.

Signed-off-by: Ajay Kumar Nandam <ajay.nandam@xxxxxxxxxxxxxxxx>
---
Ajay Kumar Nandam (4):
      ASoC: qcom: q6apm: clear g_apm on driver removal
      ASoC: qcom: qdsp6: generalize GPR service domain
      dt-bindings: sound: qcom,q6apm-dai: add memory-region and relax iommus
      ASoC: qcom: q6apm-dai: add SCM buffer assignment for mDSP platforms

 .../devicetree/bindings/sound/qcom,q6apm-dai.yaml  |  12 +-
 sound/soc/qcom/Kconfig                             |   1 +
 sound/soc/qcom/qdsp6/audioreach.c                  |  12 +-
 sound/soc/qcom/qdsp6/audioreach.h                  |  22 +-
 sound/soc/qcom/qdsp6/q6apm-dai.c                   | 300 +++++++++++++++++++--
 sound/soc/qcom/qdsp6/q6apm.c                       |   9 +-
 sound/soc/qcom/qdsp6/q6apm.h                       |   2 +-
 sound/soc/qcom/qdsp6/q6prm.c                       |   2 +
 8 files changed, 326 insertions(+), 34 deletions(-)
---
base-commit: 3d5670d672ae08b8c534b7beed6f57c8b44e7b43
change-id: 20260921-vmid-v4-0116efe5937b

Best regards,
--  
Ajay Kumar Nandam <ajay.nandam@xxxxxxxxxxxxxxxx>