ION Memory Manager (ION)

ION is a memory manager that allows for sharing of buffers between different
processes and between user space and kernel space. ION manages different
memory spaces by separating the memory spaces into "heaps".

Required properties for Ion

- compatible: "qcom,msm-ion"


All child nodes of a qcom,msm-ion node are interpreted as Ion heap
configurations.

Required properties for Ion heaps

- reg: The ID of the ION heap.
- qcom,ion-heap-type: The heap type to use for this heap. Should be one of
  the following:
    - "SYSTEM"
    - "CARVEOUT"
    - "SECURE_CARVEOUT"
    - "DMA"
    - "HYP_CMA"
    - "SYSTEM_SECURE"
    - "SECURE_DMA"

Optional properties for Ion heaps

- memory-region: phandle to memory region associated with heap.


Example:
	qcom,ion {
                 compatible = "qcom,msm-ion";
                 #address-cells = <1>;
                 #size-cells = <0>;

                 system_heap: qcom,ion-heap@25 {
                        reg = <25>;
                        qcom,ion-heap-type = "SYSTEM";
                 };

                 qcom,ion-heap@22 { /* ADSP HEAP */
                        reg = <22>;
                        memory-region = <&adsp_mem>;
                        qcom,ion-heap-type = "DMA";
                 };

                 qcom,ion-heap@10 { /* SECURE DISPLAY HEAP */
                        reg = <10>;
                        memory-region = <&secure_display_memory>;
                        qcom,ion-heap-type = "HYP_CMA";
                 };

                 qcom,ion-heap@9 {
                        reg = <9>;
                        qcom,ion-heap-type = "SYSTEM_SECURE";
                 };

        };

"SECURE_CARVEOUT"

This heap type is expected to contain multiple child nodes. Each child node
shall contain the following required properties:

- memory-region:
Refer to Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt

- token:
A u32 containing the set of secure domains which will be able to access the
memory-region.

Example:
qcom,ion {
	compatible = "qcom,msm-ion";
	#address-cells = <1>;
	#size-cells = <0>;

	qcom,ion-heap@14 {
		reg = <14>;
		qcom,ion-heap-type = "SECURE_CARVEOUT";

		node1 {
			memory-region = <&cp_region>;
			token = <ION_FLAG_CP_TOUCH>;
		};
	};
};