[RFC,1/5] dt-bindings: dma: Add CMA Heap bindings

Commit Message

Florent Tomasin Jan. 30, 2025, 1:08 p.m. UTC

Introduce a CMA Heap dt-binding allowing custom
CMA heap registrations.

* Note to the reviewers:
The patch was used for the development of the protected mode
feature in Panthor CSF kernel driver and is not initially thought
to land in the Linux kernel. It is mostly relevant if someone
wants to reproduce the environment of testing. Please, raise
interest if you think the patch has value in the Linux kernel.

Signed-off-by: Florent Tomasin <[e-mail]>
---
 .../devicetree/bindings/dma/linux,cma.yml     | 43 +++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/dma/linux,cma.yml

Comments

Maxime Ripard Jan. 30, 2025, 1:28 p.m. UTC | #1

Hi,

On Thu, Jan 30, 2025 at 01:08:57PM +0000, Florent Tomasin wrote:
> Introduce a CMA Heap dt-binding allowing custom
> CMA heap registrations.
> 
> * Note to the reviewers:
> The patch was used for the development of the protected mode
> feature in Panthor CSF kernel driver and is not initially thought
> to land in the Linux kernel. It is mostly relevant if someone
> wants to reproduce the environment of testing. Please, raise
> interest if you think the patch has value in the Linux kernel.
> 
> Signed-off-by: Florent Tomasin <[e-mail]>
> ---
>  .../devicetree/bindings/dma/linux,cma.yml     | 43 +++++++++++++++++++
>  1 file changed, 43 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/dma/linux,cma.yml
> 
> diff --git a/Documentation/devicetree/bindings/dma/linux,cma.yml b/Documentation/devicetree/bindings/dma/linux,cma.yml
> new file mode 100644
> index 000000000000..c532e016bbe5
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/dma/linux,cma.yml
> @@ -0,0 +1,43 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/dma/linux-cma.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Custom Linux CMA heap
> +
> +description:
> +  The custom Linux CMA heap device tree node allows registering
> +  of multiple CMA heaps.
> +
> +  The CMA heap name will match the node name of the "memory-region".
> +
> +properties:
> +  compatible:
> +    enum:
> +      - linux,cma
> +
> +  memory-region:
> +    maxItems: 1
> +    description: |
> +      Phandle to the reserved memory node associated with the CMA Heap.
> +      The reserved memory node must follow this binding convention:
> +       - Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
> +
> +examples:
> +  - |
> +    reserved-memory {
> +      #address-cells = <2>;
> +      #size-cells = <2>;
> +
> +      custom_cma_heap: custom-cma-heap {
> +        compatible = "shared-dma-pool";
> +        reg = <0x0 0x90600000 0x0 0x1000000>;
> +        reusable;
> +      };
> +    };
> +
> +    device_cma_heap: device-cma-heap {
> +      compatible = "linux,cma";
> +      memory-region = <&custom_cma_heap>;
> +    };

Isn't it redundant with the linux,cma-default shared-dma-pool property
already?

Maxime

Rob Herring (Arm) Jan. 30, 2025, 11:20 p.m. UTC | #2

On Thu, Jan 30, 2025 at 01:08:57PM +0000, Florent Tomasin wrote:
> Introduce a CMA Heap dt-binding allowing custom
> CMA heap registrations.
> 
> * Note to the reviewers:
> The patch was used for the development of the protected mode
> feature in Panthor CSF kernel driver and is not initially thought
> to land in the Linux kernel. It is mostly relevant if someone
> wants to reproduce the environment of testing. Please, raise
> interest if you think the patch has value in the Linux kernel.

Why would panthor need CMA, it has an MMU.

In any case, I agree with Maxime that this is redundant.

Rob

Patch

diff --git a/Documentation/devicetree/bindings/dma/linux,cma.yml b/Documentation/devicetree/bindings/dma/linux,cma.yml
new file mode 100644
index 000000000000..c532e016bbe5
--- /dev/null
+++ b/Documentation/devicetree/bindings/dma/linux,cma.yml
@@ -0,0 +1,43 @@ 
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/dma/linux-cma.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Custom Linux CMA heap
+
+description:
+  The custom Linux CMA heap device tree node allows registering
+  of multiple CMA heaps.
+
+  The CMA heap name will match the node name of the "memory-region".
+
+properties:
+  compatible:
+    enum:
+      - linux,cma
+
+  memory-region:
+    maxItems: 1
+    description: |
+      Phandle to the reserved memory node associated with the CMA Heap.
+      The reserved memory node must follow this binding convention:
+       - Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
+
+examples:
+  - |
+    reserved-memory {
+      #address-cells = <2>;
+      #size-cells = <2>;
+
+      custom_cma_heap: custom-cma-heap {
+        compatible = "shared-dma-pool";
+        reg = <0x0 0x90600000 0x0 0x1000000>;
+        reusable;
+      };
+    };
+
+    device_cma_heap: device-cma-heap {
+      compatible = "linux,cma";
+      memory-region = <&custom_cma_heap>;
+    };