Some Qualcomm SoCs, such as Shikra, run the modem in a separate security
domain with restricted access to system memory. BAM-DMUX DMA mappings
and BAM descriptor FIFOs must therefore be constrained to a designated
memory region that can be shared with the modem. Accesses outside that
region can trigger an XPU violation.

Add memory-region and qcom,vmid properties to the BAM-DMUX binding.
When qcom,vmid is present, the driver SCM-assigns the entire restricted
DMA pool to the local and remote execution environments before requesting
the DMA channels.

The restricted pool then contains the BAM-DMUX mappings. When the BAM DMA
controller references the same pool, its descriptor FIFOs are covered by
the assignment as well.

A related binding change allows the BAM DMA controller to use the same
restricted pool for descriptor FIFO allocations:

https://lore.kernel.org/all/20260920-qcom-bam-dma-vmid-ext-v2-1-4dbbff0e57c8@oss.qualcomm.com/
("dt-bindings: dma: qcom,bam-dma: Allow memory-region property")

Signed-off-by: Vishnu Santhosh <vishnu.santhosh@oss.qualcomm.com>
---
Changes in v2:
- Replace the Shikra-specific compatible and coherent RX allocation with
  memory-region and qcom,vmid properties.
- Use a restricted DMA pool for BAM-DMUX mappings and BAM descriptor FIFOs.
- SCM-assign the complete pool before requesting the DMA channels.
- Validate the remote VMID and restricted DMA pool configuration.
- Link to v1: https://lore.kernel.org/r/20260714-qcom-bam-dmux-vmid-ext-v1-0-3f29da7cca76@oss.qualcomm.com

---
Vishnu Santhosh (2):
      dt-bindings: net: qcom,bam-dmux: Add memory-region and qcom,vmid properties
      net: wwan: qcom_bam_dmux: Assign restricted DMA pool to remote processor

 .../devicetree/bindings/net/qcom,bam-dmux.yaml     | 38 +++++++++
 drivers/net/wwan/Kconfig                           |  1 +
 drivers/net/wwan/qcom_bam_dmux.c                   | 95 ++++++++++++++++++++++
 3 files changed, 134 insertions(+)
---
base-commit: 8830e65ed46de41f849eefb8ba227d4852c460f6
change-id: 20260714-qcom-bam-dmux-vmid-ext-d9289db310c1

Best regards,
-- 
Vishnu Santhosh <vishnu.santhosh@oss.qualcomm.com>