On Mon, May 15, 2023 at 12:12:16PM +0200, Stephan Gerhold wrote:
> 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.
That should already be possible with all the information you
already have. IOW, you are looking at all the region and "alloc-ranges"
addresses to decide top-down or bottom-up. Why can't the kernel do that.
Alternatively, if you really care about the allocation locations, don't
use dynamic regions.
>
> Signed-off-by: Stephan Gerhold <stephan@xxxxxxxxxxx>
> ---
> .../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.
What happens when both are set?
> +
> 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
>
