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Subject: [PATCH v4 3/4] dt-bindings: reserved-memory: Make DMA-BUF CMA heap DT-configurable
Date:   Thu, 21 Jan 2021 09:55:01 -0800
Message-Id: <20210121175502.274391-4-minchan@kernel.org>
In-Reply-To: <20210121175502.274391-1-minchan@kernel.org>
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From: Hyesoo Yu <hyesoo.yu@samsung.com>

Document devicetree binding for chunk cma heap on dma heap framework.

The DMA chunk heap supports the bulk allocation of higher order pages.

The chunk heap's allocator allocates from the CMA area. It is optimized
to perform bulk allocation of higher order pages in an efficient manner.
For this purpose, the heap needs an exclusive CMA area that will only be
used for allocation by the heap. This is the reason why we need to use
the DT to create and configure a reserved memory region for use by the
chunk CMA heap driver. Since all allocation from DMA-BUF heaps happen
from the user-space, there is no other appropriate device-driver that
we can use to register the chunk CMA heap and configure the reserved
memory region for its use.

Signed-off-by: Hyesoo Yu <hyesoo.yu@samsung.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Hridya Valsaraju <hridya@google.com>
---
 .../reserved-memory/dma_heap_chunk.yaml       | 56 +++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/reserved-memory/dma_heap_chunk.yaml

diff --git a/Documentation/devicetree/bindings/reserved-memory/dma_heap_chunk.yaml b/Documentation/devicetree/bindings/reserved-memory/dma_heap_chunk.yaml
new file mode 100644
index 000000000000..00db0ae6af61
--- /dev/null
+++ b/Documentation/devicetree/bindings/reserved-memory/dma_heap_chunk.yaml
@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/reserved-memory/dma_heap_chunk.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Device tree binding for chunk heap on DMA HEAP FRAMEWORK
+
+description: |
+  The DMA chunk heap is backed by the Contiguous Memory Allocator (CMA) and
+  supports bulk allocation of fixed size pages.
+
+maintainers:
+  - Hyesoo Yu <hyesoo.yu@samsung.com>
+  - John Stultz <john.stultz@linaro.org>
+  - Minchan Kim <minchan@kernel.org>
+  - Hridya Valsaraju<hridya@google.com>
+
+
+properties:
+  compatible:
+    enum:
+      - dma_heap,chunk
+
+  chunk-order:
+    description: |
+            order of pages that will get allocated from the chunk DMA heap.
+    maxItems: 1
+
+  size:
+    maxItems: 1
+
+  alignment:
+    maxItems: 1
+
+required:
+  - compatible
+  - size
+  - alignment
+  - chunk-order
+
+additionalProperties: false
+
+examples:
+  - |
+    reserved-memory {
+        #address-cells = <2>;
+        #size-cells = <1>;
+
+        chunk_memory: chunk_memory {
+            compatible = "dma_heap,chunk";
+            size = <0x3000000>;
+            alignment = <0x0 0x00010000>;
+            chunk-order = <4>;
+        };
+    };
-- 
2.30.0.296.g2bfb1c46d8-goog