ARM: sunxi: Initial support for Allwinner's Security ID fuses

Allwinner has electric fuses (efuse) on their line of chips. This driver
reads those fuses, seeds the kernel entropy and exports them as a sysfs
node.

These fuses are most likely to be programmed at the factory, encoding
things like Chip ID, some sort of serial number, etc. and appear to be
reasonably unique.
While in theory, these should be writeable by the user, it will probably
be inconvenient to do so. Allwinner recommends that a certain input pin,
labeled 'efuse_vddq', be connected to GND. To write these fuses however,
a 2.5 V programming voltage needs to be applied to this pin.

Even so, they can still be used to generate a board-unique mac from,
board unique RSA key and seed the kernel RNG.

On sun7i additional storage is available, this is initially used for an
UEFI BOOT key, Secure JTAG key, HDMI-HDCP key and vendor specific keys.

Currently supported are the following known chips:
Allwinner sun4i (A10)
Allwinner sun5i (A10s, A13)
Allwinner sun7i (A20)

Signed-off-by: Oliver Schinagl <oliver@schinagl.nl>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/misc/allwinner,sunxi-sid.txt b/Documentation/devicetree/bindings/misc/allwinner,sunxi-sid.txt
new file mode 100644
index 000000000000..68ba37295565
--- /dev/null
+++ b/Documentation/devicetree/bindings/misc/allwinner,sunxi-sid.txt
@@ -0,0 +1,17 @@
+Allwinner sunxi-sid
+
+Required properties:
+- compatible: "allwinner,sun4i-sid" or "allwinner,sun7i-a20-sid".
+- reg: Should contain registers location and length
+
+Example for sun4i:
+	sid@01c23800 {
+		compatible = "allwinner,sun4i-sid";
+		reg = <0x01c23800 0x10>
+	};
+
+Example for sun7i:
+	sid@01c23800 {
+		compatible = "allwinner,sun7i-a20-sid";
+		reg = <0x01c23800 0x200>
+	};