thermal: Add generic cpufreq cooling implementation

This patch adds support for generic cpu thermal cooling low level
implementations using frequency scaling up/down based on the registration
parameters. Different cpu related cooling devices can be registered by the
user and the binding of these cooling devices to the corresponding
trip points can be easily done as the registration APIs return the
cooling device pointer. The user of these APIs are responsible for
passing clipping frequency . The drivers can also register to recieve
notification about any cooling action called. Even the driver can effect
the cooling action by modifying the default data such as freq_clip_max if
needed.

Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org>

1 files changed, 60 insertions, 0 deletions

diff --git a/Documentation/thermal/cpu-cooling-api.txt b/Documentation/thermal/cpu-cooling-api.txt
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+CPU cooling APIs How To
+===================================
+
+Written by Amit Daniel Kachhap <amit.kachhap@linaro.org>
+
+Updated: 9 March 2012
+
+Copyright (c)  2011 Samsung Electronics Co., Ltd(http://www.samsung.com)
+
+0. Introduction
+
+The generic cpu cooling(freq clipping, cpuhotplug) provides
+registration/unregistration APIs to the caller. The binding of the cooling
+devices to the trip point is left for the user. The registration APIs returns
+the cooling device pointer.
+
+1. cpu cooling APIs
+
+1.1 cpufreq registration/unregistration APIs
+1.1.1 struct thermal_cooling_device *cpufreq_cooling_register(
+	struct freq_clip_table *tab_ptr, unsigned int tab_size,
+	const struct cpumask *mask_val)
+
+    This interface function registers the cpufreq cooling device with the name
+    "thermal-cpufreq-%x". This api can support multiple instances of cpufreq
+    cooling devices.
+
+    tab_ptr: The table containing the maximum value of frequency to be clipped
+    for each cooling state.
+	.freq_clip_max: Value of frequency to be clipped for each allowed
+	 cpus.
+    tab_size: the total number of cpufreq cooling states.
+    mask_val: all the allowed cpu's where frequency clipping can happen.
+
+1.1.2 void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
+
+    This interface function unregisters the "thermal-cpufreq-%x" cooling device.
+
+    cdev: Cooling device pointer which has to be unregistered.
+
+
+2. CPU cooling action notifier interface
+
+2.1 int cputherm_register_notifier(struct notifier_block *nb,
+	unsigned int list)
+
+    This interface registers a driver with cpu cooling layer. The driver will
+    be notified when any cpu cooling action is called.
+
+    nb: notifier function to register
+    list: CPUFREQ_COOLING_TYPE or CPUHOTPLUG_COOLING_TYPE
+
+2.2 int cputherm_unregister_notifier(struct notifier_block *nb,
+	unsigned int list)
+
+    This interface registers a driver with cpu cooling layer. The driver will
+    be notified when any cpu cooling action is called.
+
+    nb: notifier function to register
+    list: CPUFREQ_COOLING_TYPE or CPUHOTPLUG_COOLING_TYPE