[PATCH v2] 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 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.
- Link to v1: https://lore.kernel.org/r/20260714-qcom-bam-dma-vmid-ext-v1-0-cef87c57b7dc@xxxxxxxxxxxxxxxx
---
 .../devicetree/bindings/dma/qcom,bam-dma.yaml       | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml b/Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml
index e72adc172af102d8f400044ea0dc32db6b2365be..1e4324799f2b3b8a9ebf9f084e457e66aad20d28 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:
@@ -137,6 +144,20 @@ examples:
             qcom,num-ees = <4>;
             num-channels = <20>;
             qcom,controlled-remotely;
+            memory-region = <&bam_dmux_pool>;
+        };
+    };
+
+    reserved-memory {
+        #address-cells = <1>;
+        #size-cells = <1>;
+        ranges;
+
+        bam_dmux_pool: restricted-dma-pool {
+            compatible = "restricted-dma-pool";
+            size = <0x40000>;
+            alignment = <0x40000>;
+            alloc-ranges = <0x80000000 0x80000000>;
         };
     };
 ...

---
base-commit: 40288c9206c17eb66a603262e06a58d300d0f279
change-id: 20260714-qcom-bam-dma-vmid-ext-8a3bd3c5c00e

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