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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>;
};
};
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