thermal: Add generic devfreq cooling device

This patchset introduce the generic devfreq cooling device for generic thermal
framework. The devfreq devices are used ad cooling device to reduce the
overheating temperature. This patch is based on drivers/thermal/cpu_cooling.c.
The devfreq cooling device can change the ragne of the frequency table of
devfreq device according to cooling level in device tree file.

To verify the devfreq cooling device driver, I testd it with following platform:

For example,
- The Mali GPU of Exynos5433 SoC uses the devfreq framework to support the DVFS
feature and Exynos5433 contains the G3D (GPU) thermal sensor. Following example
explain the correlation between mali dt node and thermal sensor/zone.
: thermal sensor : G3D sensor of Samsung Exynos5433 [1][2]
: devfreq cooling device : Mali GPU [3]

According to the temperature of g3d thermal sensor inclued in Exynos5433,
devfreq cooling device can change the maximum frequency of Mali GPU.

1. In Exynos5433-based board dts file, Mali GPU dt node uses the devfreq
framework to suppot the DVFS feature. Following dt node includes the
both 'cooling-cells' and 'operating-points' which means the supported
frequency entries:

	mali: mali@14AC0000 {
		compatible = "arm,mali-midgard";
		reg = <0x14AC0000 0x5000>;
		interrupts = <0 282 0>, <0 283 0>, <0 281 0>;
		interrupt-names = "JOB", "MMU", "GPU";
		clocks = <&cmu_g3d CLK_ACLK_G3D>;
		clock-names = "clk_mali";
		power-domains = <&pd_g3d>;
		status = "disabled";

		#cooling-cells = <2>;

		operating-points = <
			700000 1150000
			600000 1150000
			550000 1125000
			500000 1075000
			420000 1025000
			350000 1025000
			266000 1000000
			160000 1000000
		>;
	};

2. In exynos5433.dtsi, G3D thermal sensor measure the temperature of Mali GPU:

	tmu_g3d: tmu@10070000 {
		compatible = "samsung,exynos5433-tmu";
		reg = <0x10070000 0x200>;
		interrupts = <0 99 0>;
		clocks = <&cmu_peris CLK_PCLK_TMU1_APBIF>,
			 <&cmu_peris CLK_SCLK_TMU1>;
		clock-names = "tmu_apbif", "tmu_sclk";
		#include "exynos5433-tmu-sensor-conf.dtsi"
		status = "disabled";
	};

3. In exynos5433-tmu.dtsi, thermal-zones includes both trip points and
cooling-maps of g3d thermal sensor. Following cooling-maps show the match
between each trip point and each cooling device (devfreq device of mali):

	thermal-zones {
		/* ...... */
		g3d_thermal: g3d-thermal {
			thermal-sensors = <&tmu_g3d>;
			polling-delay-passive = <0>;
			polling-delay = <0>;
			trips {
				g3d_alert_0: g3d-alert-0 {
					temperature = <30000>;	/* millicelsius */
					hysteresis = <10000>;	/* millicelsius */
					type = "active";
				};
				g3d_alert_1: g3d-alert-1 {
					temperature = <40000>;	/* millicelsius */
					hysteresis = <10000>;	/* millicelsius */
					type = "active";
				};

				/* ...... */
			};

			cooling-maps {
				map0 {
					/* Set maximum frequency as 550MHz  */
					trip = <&g3d_alert_0>;
					cooling-device = <&mali 2 2>;
				};
				map1 {
					/* Set maximum frequency as 420MHz  */
					trip = <&g3d_alert_1>;
					cooling-device = <&mali 4 4>;
				};

				/* ...... */
			};
		};

		......
	};

[1] https://git.kernel.org/cgit/linux/kernel/git/kgene/linux-...
[2] https://git.kernel.org/cgit/linux/kernel/git/kgene/linux-...
[3] malideveloper.arm.com/downloads/drivers/TX041/r5p0-06rel0/TX041-SW-99002-r5p0-06rel0.tgz

Chanwoo Choi (2):
  PM: devfreq: Add the prototype of update_devfreq() to export
  thermal: devfreq_cooling: Add generic devfreq cooling device implementaion

 .../devicetree/bindings/thermal/thermal.txt        |   8 +-
 drivers/devfreq/devfreq.c                          |  22 +-
 drivers/thermal/Kconfig                            |  11 +
 drivers/thermal/Makefile                           |   3 +
 drivers/thermal/devfreq-cooling.c                  | 309 +++++++++++++++++++++
 include/linux/devfreq-cooling.h                    |  80 ++++++
 include/linux/devfreq.h                            |   7 +
 7 files changed, 425 insertions(+), 15 deletions(-)
 create mode 100644 drivers/thermal/devfreq-cooling.c
 create mode 100644 include/linux/devfreq-cooling.h

-- 
1.8.5.5

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