[PATCH v3] dt-bindings: dma: qcom,bam-dma: Allow memory-region property

[Vishnu Santhosh]

Some Qualcomm SoCs, such as Shikra, run the modem in a separate security
domain, preventing it from accessing BAM descriptor FIFOs allocated from
arbitrary host memory.

Add an optional memory-region property to constrain DMA allocations made
by the BAM DMA controller to a restricted DMA pool. Access permissions
for the remote execution environment are managed separately.

Co-developed-by: Deepak Kumar Singh <deepak.singh@xxxxxxxxxxxxxxxx>
Signed-off-by: Deepak Kumar Singh <deepak.singh@xxxxxxxxxxxxxxxx>
Signed-off-by: Vishnu Santhosh <vishnu.santhosh@xxxxxxxxxxxxxxxx>
---
Changes in v3:
- Drop the example changes (Krzysztof)
- Link to v2: https://lore.kernel.org/r/20260920-qcom-bam-dma-vmid-ext-v2-1-4dbbff0e57c8@xxxxxxxxxxxxxxxx

Changes in v2:
- Replace the qcom,vmid property and BAM DMA driver SCM assignment with
  the standard memory-region restricted DMA pool mechanism.
- Rely on generic DMA handling to constrain descriptor FIFO allocations
  to the restricted pool.
- Drop the Shikra-specific BAM compatible and all BAM DMA driver changes.
- Drop Rob's Reviewed-by, as the binding was substantially redesigned.
- Link to v1: https://lore.kernel.org/r/20260714-qcom-bam-dma-vmid-ext-v1-0-cef87c57b7dc@xxxxxxxxxxxxxxxx
---
 Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml b/Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml
index e72adc172af102d8f400044ea0dc32db6b2365be..b7b348bf6ae2feba32ecaf17ca8696817a1ada4a 100644
--- a/Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml
+++ b/Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml
@@ -50,6 +50,13 @@ properties:
     minItems: 1
     maxItems: 7
 
+  memory-region:
+    maxItems: 1
+    description:
+      Phandle to a reserved-memory node compatible with restricted-dma-pool.
+      The BAM DMA controller uses the pool for DMA allocations, including
+      channel descriptor FIFOs.
+
   num-channels:
     $ref: /schemas/types.yaml#/definitions/uint32
     description:

---
base-commit: 2c455ddca7827ad8fa3a64fdbf5a60efb928b46a
change-id: 20260714-qcom-bam-dma-vmid-ext-8a3bd3c5c00e

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