ARC: [dts] Introduce Timer bindings

ARC Timers have historically been probed directly.
As precursor to start probing Timers thru DT introduce these bindings
Note that to keep series bisectable, these bindings are not yet used in
code.

Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: devicetree@vger.kernel.org
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

Documentation/devicetree/bindings/timer/snps,arc-timer.txt

+Synopsys ARC Local Timer with Interrupt Capabilities
+- Found on all ARC CPUs (ARC700/ARCHS)
+- Can be optionally programmed to interrupt on Limit
+- Two idential copies TIMER0 and TIMER1 exist in ARC cores and historically
+  TIMER0 used as clockevent provider (true for all ARC cores)
+  TIMER1 used for clocksource (mandatory for ARC700, optional for ARC HS)
+
+Required properties:
+
+- compatible : should be "snps,arc-timer"
+- interrupts : single Interrupt going into parent intc
+	       (16 for ARCHS cores, 3 for ARC700 cores)
+- clocks     : phandle to the source clock
+
+Optional properties:
+
+- interrupt-parent : phandle to parent intc
+
+Example:
+
+	timer0 {
+		compatible = "snps,arc-timer";
+		interrupts = <3>;
+		interrupt-parent = <&core_intc>;
+		clocks = <&core_clk>;
+	};
+
+	timer1 {
+		compatible = "snps,arc-timer";
+		clocks = <&core_clk>;
+	};

Documentation/devicetree/bindings/timer/snps,archs-gfrc.txt

+Synopsys ARC Free Running 64-bit Global Timer for ARC HS CPUs
+- clocksource provider for SMP SoC
+
+Required properties:
+
+- compatible : should be "snps,archs-gfrc"
+- clocks     : phandle to the source clock
+
+Example:
+
+	gfrc {
+		compatible = "snps,archs-gfrc";
+		clocks = <&core_clk>;
+	};

Documentation/devicetree/bindings/timer/snps,archs-rtc.txt

+Synopsys ARC Free Running 64-bit Local Timer for ARC HS CPUs
+- clocksource provider for UP SoC
+
+Required properties:
+
+- compatible : should be "snps,archs-rtc"
+- clocks     : phandle to the source clock
+
+Example:
+
+	rtc {
+		compatible = "snps,arc-rtc";
+		clocks = <&core_clk>;
+	};

arch/arc/boot/dts/abilis_tb10x.dtsi

@@ -35,6 +35,20 @@ cpu@0 {
 		};
 	};
 
+	/* TIMER0 with interrupt for clockevent */
+	timer0 {
+		compatible = "snps,arc-timer";
+		interrupts = <3>;
+		interrupt-parent = <&intc>;
+		clocks = <&cpu_clk>;
+	};
+
+	/* TIMER1 for free running clocksource */
+	timer1 {
+		compatible = "snps,arc-timer";
+		clocks = <&cpu_clk>;
+	};
+
 	soc100 {
 		#address-cells	= <1>;
 		#size-cells	= <1>;

arch/arc/boot/dts/skeleton.dtsi

@@ -30,6 +30,20 @@ cpu@0 {
 		};
 	};
 
+	/* TIMER0 with interrupt for clockevent */
+	timer0 {
+		compatible = "snps,arc-timer";
+		interrupts = <3>;
+		interrupt-parent = <&core_intc>;
+		clocks = <&core_clk>;
+	};
+
+	/* TIMER1 for free running clocksource */
+	timer1 {
+		compatible = "snps,arc-timer";
+		clocks = <&core_clk>;
+	};
+
 	memory {
 		device_type = "memory";
 		reg = <0x80000000 0x10000000>;	/* 256M */

arch/arc/boot/dts/skeleton_hs.dtsi

@@ -25,6 +25,26 @@ cpu@0 {
 		};
 	};
 
+	/* TIMER0 with interrupt for clockevent */
+	timer0 {
+		compatible = "snps,arc-timer";
+		interrupts = <16>;
+		interrupt-parent = <&core_intc>;
+		clocks = <&core_clk>;
+	};
+
+	/* 64-bit Local RTC: preferred clocksource for UP */
+	rtc {
+		compatible = "snps,archs-timer-rtc";
+		clocks = <&core_clk>;
+	};
+
+	/* TIMER1 for free running clocksource: Fallback if rtc not found */
+	timer1 {
+		compatible = "snps,arc-timer";
+		clocks = <&core_clk>;
+	};
+
 	memory {
 		device_type = "memory";
 		reg = <0x80000000 0x10000000>;	/* 256M */

arch/arc/boot/dts/skeleton_hs_idu.dtsi

@@ -25,6 +25,20 @@ cpu@0 {
 		};
 	};
 
+	/* TIMER0 with interrupt for clockevent */
+	timer0 {
+		compatible = "snps,arc-timer";
+		interrupts = <16>;
+		interrupt-parent = <&core_intc>;
+		clocks = <&core_clk>;
+	};
+
+	/* 64-bit Global Free Running Counter */
+	gfrc {
+		compatible = "snps,archs-timer-gfrc";
+		clocks = <&core_clk>;
+	};
+
 	memory {
 		device_type = "memory";
 		reg = <0x80000000 0x10000000>;	/* 256M */