[PATCH net-next v3 0/2] net: wwan: qcom_bam_dmux: Add restricted DMA pool support

[Vishnu Santhosh]

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, and
a qcom,shikra-bam-dmux compatible that requires them. 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/20261021-qcom-bam-dma-vmid-ext-v3-1-299355e8dd3b@xxxxxxxxxxxxxxxx/
("dt-bindings: dma: qcom,bam-dma: Allow memory-region property")

Signed-off-by: Vishnu Santhosh <vishnu.santhosh@xxxxxxxxxxxxxxxx>
---
Changes in v3:
- dt-bindings: Add qcom,shikra-bam-dmux, with qcom,bam-dmux as fallback,
  and require memory-region and qcom,vmid for it (Krzysztof)
- dt-bindings: Drop minItems from qcom,vmid (Krzysztof)
- dt-bindings: Drop the example changes (Krzysztof)
- dt-bindings: Drop the statement about the local VMID from the
  qcom,vmid description (Sashiko)
- Reuse remove() on late probe failure, since the PC IRQ may already
  have powered up the RX path (Sashiko)
- Skip the pool reclaim when the remote did not acknowledge the
  power-down (Sashiko)
- Fail probe if the restricted pool is not attached to the device
  (Sashiko)
- Link to v2: https://lore.kernel.org/r/20260920-qcom-bam-dmux-vmid-ext-v2-0-ef5ca2178378@xxxxxxxxxxxxxxxx

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@xxxxxxxxxxxxxxxx

---
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     |  36 ++++++-
 drivers/net/wwan/Kconfig                           |   1 +
 drivers/net/wwan/qcom_bam_dmux.c                   | 119 ++++++++++++++++++++-
 3 files changed, 152 insertions(+), 4 deletions(-)
---
base-commit: 78974bac98eb0581f85aab56ccc0377cdcedb964
change-id: 20260714-qcom-bam-dmux-vmid-ext-d9289db310c1

Best regards,
-- 
Vishnu Santhosh <vishnu.santhosh@xxxxxxxxxxxxxxxx>