1 files changed, 97 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/reserved-memory/shared-dma-pool.yaml b/Documentation/devicetree/bindings/reserved-memory/shared-dma-pool.yaml
new file mode 100644
index 000000000..618105f07
--- /dev/null
+++ b/Documentation/devicetree/bindings/reserved-memory/shared-dma-pool.yaml
@@ -0,0 +1,97 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/reserved-memory/shared-dma-pool.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: /reserved-memory DMA pool node bindings
+
+maintainers:
+  - devicetree-spec@vger.kernel.org
+
+allOf:
+  - $ref: "reserved-memory.yaml"
+
+properties:
+  compatible:
+    oneOf:
+      - const: shared-dma-pool
+        description: >
+          This indicates a region of memory meant to be used as a shared
+          pool of DMA buffers for a set of devices. It can be used by an
+          operating system to instantiate the necessary pool management
+          subsystem if necessary.
+
+      - const: restricted-dma-pool
+        description: >
+          This indicates a region of memory meant to be used as a pool
+          of restricted DMA buffers for a set of devices. The memory
+          region would be the only region accessible to those devices.
+          When using this, the no-map and reusable properties must not
+          be set, so the operating system can create a virtual mapping
+          that will be used for synchronization. The main purpose for
+          restricted DMA is to mitigate the lack of DMA access control
+          on systems without an IOMMU, which could result in the DMA
+          accessing the system memory at unexpected times and/or
+          unexpected addresses, possibly leading to data leakage or
+          corruption. The feature on its own provides a basic level of
+          protection against the DMA overwriting buffer contents at
+          unexpected times. However, to protect against general data
+          leakage and system memory corruption, the system needs to
+          provide way to lock down the memory access, e.g., MPU. Note
+          that since coherent allocation needs remapping, one must set
+          up another device coherent pool by shared-dma-pool and use
+          dma_alloc_from_dev_coherent instead for atomic coherent
+          allocation.
+
+  linux,cma-default:
+    type: boolean
+    description: >
+      If this property is present, then Linux will use the region for
+      the default pool of the contiguous memory allocator.
+
+  linux,dma-default:
+    type: boolean
+    description: >
+      If this property is present, then Linux will use the region for
+      the default pool of the consistent DMA allocator.
+
+if:
+  properties:
+    compatible:
+      contains:
+        const: restricted-dma-pool
+then:
+  properties:
+    no-map: false
+    reusable: false
+
+unevaluatedProperties: false
+
+examples:
+  - |
+      reserved-memory {
+          #address-cells = <1>;
+          #size-cells = <1>;
+          ranges;
+
+          /* global autoconfigured region for contiguous allocations */
+          linux,cma {
+              compatible = "shared-dma-pool";
+              reusable;
+              size = <0x4000000>;
+              alignment = <0x2000>;
+              linux,cma-default;
+          };
+
+          display_reserved: framebuffer@78000000 {
+              reg = <0x78000000 0x800000>;
+          };
+
+          restricted_dma_reserved: restricted-dma-pool@50000000 {
+              compatible = "restricted-dma-pool";
+              reg = <0x50000000 0x4000000>;
+          };
+      };
+
+...