ARM: dts: imx7s: enable cpuidle driver

Enable cpuidle for i.MX7S/D using generic ARM cpuidle
driver, below 2 idle states enabled:

1. ARM WFI;
2. SoC WAIT mode.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx7d.dtsi

@@ -20,6 +20,7 @@ cpu1: cpu@1 {
 			reg = <1>;
 			clock-frequency = <996000000>;
 			operating-points-v2 = <&cpu0_opp_table>;
+			cpu-idle-states = <&cpu_sleep_wait>;
 		};
 	};
 

arch/arm/boot/dts/imx7s.dtsi

@@ -54,6 +54,19 @@ cpus {
 		#address-cells = <1>;
 		#size-cells = <0>;
 
+		idle-states {
+			entry-method = "psci";
+
+			cpu_sleep_wait: cpu-sleep-wait {
+				compatible = "arm,idle-state";
+				arm,psci-suspend-param = <0x0010000>;
+				local-timer-stop;
+				entry-latency-us = <100>;
+				exit-latency-us = <50>;
+				min-residency-us = <1000>;
+			};
+		};
+
 		cpu0: cpu@0 {
 			compatible = "arm,cortex-a7";
 			device_type = "cpu";
@@ -61,6 +74,7 @@ cpu0: cpu@0 {
 			clock-frequency = <792000000>;
 			clock-latency = <61036>; /* two CLK32 periods */
 			clocks = <&clks IMX7D_CLK_ARM>;
+			cpu-idle-states = <&cpu_sleep_wait>;
 		};
 	};