linux-kernel - [PATCH 1/5] dt-bindings: reserved-memory: Add alloc-{bottom-up,top-down}

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Message-Id: <20230510-dt-resv-bottom-up-v1-1-3bf68873dbed@gerhold.net>
Date:   Mon, 15 May 2023 12:12:16 +0200
From:   Stephan Gerhold <stephan@...hold.net>
To:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        devicetree@...r.kernel.org, devicetree-spec@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Stephan Gerhold <stephan@...hold.net>
Subject: [PATCH 1/5] dt-bindings: reserved-memory: Add
 alloc-{bottom-up,top-down}

Right now the allocation behavior for dynamic reserved memory is
implementation-defined. On Linux it is dependent on the architecture.
This is usually fine if the address is completely arbitrary.

However, when using "alloc-ranges" it is helpful to allow controlling
this. That way you can make sure that the reservations are placed next
to other (static) allocations to keep the free memory contiguous if
possible.

Signed-off-by: Stephan Gerhold <stephan@...hold.net>
---
 .../bindings/reserved-memory/reserved-memory.yaml  | 39 ++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.yaml b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.yaml
index c680e397cfd2..56f4bc6137e7 100644
--- a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.yaml
+++ b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.yaml
@@ -52,6 +52,18 @@ properties:
       Address and Length pairs. Specifies regions of memory that are
       acceptable to allocate from.
 
+  alloc-bottom-up:
+    type: boolean
+    description: >
+      Specifies that the memory region should be preferably allocated
+      at the lowest available address within the "alloc-ranges" region.
+
+  alloc-top-down:
+    type: boolean
+    description: >
+      Specifies that the memory region should be preferably allocated
+      at the highest available address within the "alloc-ranges" region.
+
   iommu-addresses:
     $ref: /schemas/types.yaml#/definitions/phandle-array
     description: >
@@ -93,6 +105,10 @@ properties:
       system can use that region to store volatile or cached data that
       can be otherwise regenerated or migrated elsewhere.
 
+dependencies:
+  alloc-bottom-up: [alloc-ranges]
+  alloc-top-down: [alloc-ranges]
+
 allOf:
   - if:
       required:
@@ -178,4 +194,27 @@ examples:
         };
       };
     };
+
+  - |
+    / {
+      compatible = "foo";
+      model = "foo";
+
+      #address-cells = <2>;
+      #size-cells = <2>;
+
+      reserved-memory {
+        #address-cells = <2>;
+        #size-cells = <2>;
+        ranges;
+
+        adsp_mem: adsp {
+          size = <0x0 0x600000>;
+          alignment = <0x0 0x100000>;
+          alloc-ranges = <0x0 0x86800000 0x0 0x10000000>;
+          alloc-bottom-up;
+          no-map;
+        };
+      };
+    };
 ...

-- 
2.40.1