[PATCH v3] arm64: dts: exynos7: add support for cpuidle core power down

[k.chander@samsung.com (Chander Kashyap)]

Exynos7 has core power down state where cores can be powered off independently.
This patch adds support for this state.

Entry latency for the core power down is calculated as follows:
1. Time difference is measured between cpuidle entry and exit.
2. WFI is skipped measuring the time.
3. The time is averaged out for 100000 cpuidle transactions with varying load.

Exit latency and target residency are supplied as per HW team

Signed-off-by: Chander Kashyap <k.chander@samsung.com>
---
This patch has following dependencies:
	- [PATCH v5 0/8] arch: arm64: Enable support for Samsung Exynos7 SoC
		http://www.spinics.net/lists/linux-samsung-soc/msg37047.html
Changes in v2:
	- Moved the cpu-idle-state property after reg property
	- removed the status property.

Changes in v3:
	- Added the Entry latency calculation in commit message.

 arch/arm64/boot/dts/exynos/exynos7.dtsi |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arch/arm64/boot/dts/exynos/exynos7.dtsi b/arch/arm64/boot/dts/exynos/exynos7.dtsi
index 50ae936..444dde1 100644
--- a/arch/arm64/boot/dts/exynos/exynos7.dtsi
+++ b/arch/arm64/boot/dts/exynos/exynos7.dtsi
@@ -37,6 +37,7 @@
 			compatible = "arm,cortex-a57", "arm,armv8";
 			enable-method = "psci";
 			reg = <0x0>;
+			cpu-idle-states = <&CPU_SLEEP>;
 		};
 
 		cpu at 1 {
@@ -44,6 +45,7 @@
 			compatible = "arm,cortex-a57", "arm,armv8";
 			enable-method = "psci";
 			reg = <0x1>;
+			cpu-idle-states = <&CPU_SLEEP>;
 		};
 
 		cpu at 2 {
@@ -51,6 +53,7 @@
 			compatible = "arm,cortex-a57", "arm,armv8";
 			enable-method = "psci";
 			reg = <0x2>;
+			cpu-idle-states = <&CPU_SLEEP>;
 		};
 
 		cpu at 3 {
@@ -58,6 +61,20 @@
 			compatible = "arm,cortex-a57", "arm,armv8";
 			enable-method = "psci";
 			reg = <0x3>;
+			cpu-idle-states = <&CPU_SLEEP>;
+		};
+
+		idle-states {
+			entry-method = "arm,psci";
+
+			CPU_SLEEP: cpu-sleep {
+				compatible = "arm,idle-state";
+				local-timer-stop;
+				arm,psci-suspend-param = <0x0010000>;
+				entry-latency-us = <20>;
+				exit-latency-us = <150>;
+				min-residency-us = <2100>;
+			};
 		};
 	};
 
-- 
1.7.9.5