linux-arkmicro/linux/Documentation/devicetree/bindings/arm/sunxi/smp-sram.txt

Allwinner SRAM for smp bringup:
------------------------------------------------

Allwinner's A80 SoC uses part of the secure sram for hotplugging of the
primary core (cpu0). Once the core gets powered up it checks if a magic
value is set at a specific location. If it is then the BROM will jump
to the software entry address, instead of executing a standard boot.

Therefore a reserved section sub-node has to be added to the mmio-sram
declaration.

Note that this is separate from the Allwinner SRAM controller found in
../../sram/sunxi-sram.txt. This SRAM is secure only and not mappable to
any device.

Also there are no "secure-only" properties. The implementation should
check if this SRAM is usable first.

Required sub-node properties:
- compatible : depending on the SoC this should be one of:
		"allwinner,sun9i-a80-smp-sram"

The rest of the properties should follow the generic mmio-sram discription
found in ../../misc/sram.txt

Example:

	sram_b: sram@20000 {
		/* 256 KiB secure SRAM at 0x20000 */
		compatible = "mmio-sram";
		reg = <0x00020000 0x40000>;
		#address-cells = <1>;
		#size-cells = <1>;
		ranges = <0 0x00020000 0x40000>;

		smp-sram@1000 {
			/*
			 * This is checked by BROM to determine if
			 * cpu0 should jump to SMP entry vector
			 */
			compatible = "allwinner,sun9i-a80-smp-sram";
			reg = <0x1000 0x8>;
		};
	};