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authorChen-Yu Tsai <wens@csie.org>2018-01-17 11:46:52 +0300
committerChen-Yu Tsai <wens@csie.org>2018-02-20 06:12:39 +0300
commit8d6b18a2a2ccbbb3dd53122dae1437fbe588a114 (patch)
tree0e2cb15676fe2ded15793814f260d6255b2e3ba2 /Documentation/devicetree/bindings/arm/sunxi
parent7cbea6327e76f2a7d77d02065a191bb29865a4a9 (diff)
downloadlinux-8d6b18a2a2ccbbb3dd53122dae1437fbe588a114.tar.xz
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 <maxime.ripard@free-electrons.com> Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Diffstat (limited to 'Documentation/devicetree/bindings/arm/sunxi')
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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>;
+ };
+ };