From 8d6b18a2a2ccbbb3dd53122dae1437fbe588a114 Mon Sep 17 00:00:00 2001 From: Chen-Yu Tsai Date: Wed, 17 Jan 2018 16:46:52 +0800 Subject: [PATCH] dt-bindings: ARM: sunxi: Document A80 SoC secure SRAM usage by SMP hotplug On the Allwinner A80 SoC the BROM supports hotplugging the primary core (cpu0) by checking two 32bit values at a specific location within the secure SRAM block. This region needs to be reserved and accessible to the SMP code. Document its usage. Acked-by: Maxime Ripard Reviewed-by: Rob Herring Signed-off-by: Chen-Yu Tsai --- .../bindings/arm/sunxi/smp-sram.txt | 44 +++++++++++++++++++ 1 file changed, 44 insertions(+) create mode 100644 Documentation/devicetree/bindings/arm/sunxi/smp-sram.txt diff --git a/Documentation/devicetree/bindings/arm/sunxi/smp-sram.txt b/Documentation/devicetree/bindings/arm/sunxi/smp-sram.txt new file mode 100644 index 000000000000..082e6a9382d3 --- /dev/null +++ b/Documentation/devicetree/bindings/arm/sunxi/smp-sram.txt @@ -0,0 +1,44 @@ +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>; + }; + }; -- 2.45.2