dt-bindings: Document the ARM System timer bindings

This adds documentation of device tree bindings for the
ARM System timer.

Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

diff --git a/Documentation/devicetree/bindings/arm/armv7m_systick.txt b/Documentation/devicetree/bindings/arm/armv7m_systick.txt
new file mode 100644 (file)
index 0000000..7cf4a24
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/armv7m_systick.txt
@@ -0,0 +1,26 @@
+* ARMv7M System Timer
+
+ARMv7-M includes a system timer, known as SysTick. Current driver only
+implements the clocksource feature.
+
+Required properties:
+- compatible     : Should be "arm,armv7m-systick"
+- reg            : The address range of the timer
+
+Required clocking property, have to be one of:
+- clocks         : The input clock of the timer
+- clock-frequency : The rate in HZ in input of the ARM SysTick
+
+Examples:
+
+systick: timer@e000e010 {
+       compatible = "arm,armv7m-systick";
+       reg = <0xe000e010 0x10>;
+       clocks = <&clk_systick>;
+};
+
+systick: timer@e000e010 {
+       compatible = "arm,armv7m-systick";
+       reg = <0xe000e010 0x10>;
+       clock-frequency = <90000000>;
+};