6 files changed, 1125 insertions, 0 deletions

diff --git a/Documentation/power/00-INDEX b/Documentation/power/00-INDEX
index fb742c213c9e..45e9d4a91284 100644
--- a/Documentation/power/00-INDEX
+++ b/Documentation/power/00-INDEX
@@ -14,6 +14,8 @@ interface.txt
         - Power management user interface in /sys/power
 notifiers.txt
         - Registering suspend notifiers in device drivers
+opp.txt
+        - Operating Performance Point library
 pci.txt
         - How the PCI Subsystem Does Power Management
 pm_qos_interface.txt
diff --git a/Documentation/power/opp.txt b/Documentation/power/opp.txt
new file mode 100644
index 000000000000..44d87ad3cea9
--- /dev/null
+++ b/Documentation/power/opp.txt
@@ -0,0 +1,375 @@
+*=============*
+* OPP Library *
+*=============*
+
+(C) 2009-2010 Nishanth Menon <nm@ti.com>, Texas Instruments Incorporated
+
+Contents
+--------
+1. Introduction
+2. Initial OPP List Registration
+3. OPP Search Functions
+4. OPP Availability Control Functions
+5. OPP Data Retrieval Functions
+6. Cpufreq Table Generation
+7. Data Structures
+
+1. Introduction
+===============
+Complex SoCs of today consists of a multiple sub-modules working in conjunction.
+In an operational system executing varied use cases, not all modules in the SoC
+need to function at their highest performing frequency all the time. To
+facilitate this, sub-modules in a SoC are grouped into domains, allowing some
+domains to run at lower voltage and frequency while other domains are loaded
+more. The set of discrete tuples consisting of frequency and voltage pairs that
+the device will support per domain are called Operating Performance Points or
+OPPs.
+
+OPP library provides a set of helper functions to organize and query the OPP
+information. The library is located in drivers/base/power/opp.c and the header
+is located in include/linux/opp.h. OPP library can be enabled by enabling
+CONFIG_PM_OPP from power management menuconfig menu. OPP library depends on
+CONFIG_PM as certain SoCs such as Texas Instrument's OMAP framework allows to
+optionally boot at a certain OPP without needing cpufreq.
+
+Typical usage of the OPP library is as follows:
+(users)         -> registers a set of default OPPs              -> (library)
+SoC framework   -> modifies on required cases certain OPPs      -> OPP layer
+                -> queries to search/retrieve information       ->
+
+OPP layer expects each domain to be represented by a unique device pointer. SoC
+framework registers a set of initial OPPs per device with the OPP layer. This
+list is expected to be an optimally small number typically around 5 per device.
+This initial list contains a set of OPPs that the framework expects to be safely
+enabled by default in the system.
+
+Note on OPP Availability:
+------------------------
+As the system proceeds to operate, SoC framework may choose to make certain
+OPPs available or not available on each device based on various external
+factors. Example usage: Thermal management or other exceptional situations where
+SoC framework might choose to disable a higher frequency OPP to safely continue
+operations until that OPP could be re-enabled if possible.
+
+OPP library facilitates this concept in it's implementation. The following
+operational functions operate only on available opps:
+opp_find_freq_{ceil, floor}, opp_get_voltage, opp_get_freq, opp_get_opp_count
+and opp_init_cpufreq_table
+
+opp_find_freq_exact is meant to be used to find the opp pointer which can then
+be used for opp_enable/disable functions to make an opp available as required.
+
+WARNING: Users of OPP library should refresh their availability count using
+get_opp_count if opp_enable/disable functions are invoked for a device, the
+exact mechanism to trigger these or the notification mechanism to other
+dependent subsystems such as cpufreq are left to the discretion of the SoC
+specific framework which uses the OPP library. Similar care needs to be taken
+care to refresh the cpufreq table in cases of these operations.
+
+WARNING on OPP List locking mechanism:
+-------------------------------------------------
+OPP library uses RCU for exclusivity. RCU allows the query functions to operate
+in multiple contexts and this synchronization mechanism is optimal for a read
+intensive operations on data structure as the OPP library caters to.
+
+To ensure that the data retrieved are sane, the users such as SoC framework
+should ensure that the section of code operating on OPP queries are locked
+using RCU read locks. The opp_find_freq_{exact,ceil,floor},
+opp_get_{voltage, freq, opp_count} fall into this category.
+
+opp_{add,enable,disable} are updaters which use mutex and implement it's own
+RCU locking mechanisms. opp_init_cpufreq_table acts as an updater and uses
+mutex to implment RCU updater strategy. These functions should *NOT* be called
+under RCU locks and other contexts that prevent blocking functions in RCU or
+mutex operations from working.
+
+2. Initial OPP List Registration
+================================
+The SoC implementation calls opp_add function iteratively to add OPPs per
+device. It is expected that the SoC framework will register the OPP entries
+optimally- typical numbers range to be less than 5. The list generated by
+registering the OPPs is maintained by OPP library throughout the device
+operation. The SoC framework can subsequently control the availability of the
+OPPs dynamically using the opp_enable / disable functions.
+
+opp_add - Add a new OPP for a specific domain represented by the device pointer.
+        The OPP is defined using the frequency and voltage. Once added, the OPP
+        is assumed to be available and control of it's availability can be done
+        with the opp_enable/disable functions. OPP library internally stores
+        and manages this information in the opp struct. This function may be
+        used by SoC framework to define a optimal list as per the demands of
+        SoC usage environment.
+
+        WARNING: Do not use this function in interrupt context.
+
+        Example:
+         soc_pm_init()
+         {
+                /* Do things */
+                r = opp_add(mpu_dev, 1000000, 900000);
+                if (!r) {
+                        pr_err("%s: unable to register mpu opp(%d)\n", r);
+                        goto no_cpufreq;
+                }
+                /* Do cpufreq things */
+         no_cpufreq:
+                /* Do remaining things */
+         }
+
+3. OPP Search Functions
+=======================
+High level framework such as cpufreq operates on frequencies. To map the
+frequency back to the corresponding OPP, OPP library provides handy functions
+to search the OPP list that OPP library internally manages. These search
+functions return the matching pointer representing the opp if a match is
+found, else returns error. These errors are expected to be handled by standard
+error checks such as IS_ERR() and appropriate actions taken by the caller.
+
+opp_find_freq_exact - Search for an OPP based on an *exact* frequency and
+        availability. This function is especially useful to enable an OPP which
+        is not available by default.
+        Example: In a case when SoC framework detects a situation where a
+        higher frequency could be made available, it can use this function to
+        find the OPP prior to call the opp_enable to actually make it available.
+         rcu_read_lock();
+         opp = opp_find_freq_exact(dev, 1000000000, false);
+         rcu_read_unlock();
+         /* dont operate on the pointer.. just do a sanity check.. */
+         if (IS_ERR(opp)) {
+                pr_err("frequency not disabled!\n");
+                /* trigger appropriate actions.. */
+         } else {
+                opp_enable(dev,1000000000);
+         }
+
+        NOTE: This is the only search function that operates on OPPs which are
+        not available.
+
+opp_find_freq_floor - Search for an available OPP which is *at most* the
+        provided frequency. This function is useful while searching for a lesser
+        match OR operating on OPP information in the order of decreasing
+        frequency.
+        Example: To find the highest opp for a device:
+         freq = ULONG_MAX;
+         rcu_read_lock();
+         opp_find_freq_floor(dev, &freq);
+         rcu_read_unlock();
+
+opp_find_freq_ceil - Search for an available OPP which is *at least* the
+        provided frequency. This function is useful while searching for a
+        higher match OR operating on OPP information in the order of increasing
+        frequency.
+        Example 1: To find the lowest opp for a device:
+         freq = 0;
+         rcu_read_lock();
+         opp_find_freq_ceil(dev, &freq);
+         rcu_read_unlock();
+        Example 2: A simplified implementation of a SoC cpufreq_driver->target:
+         soc_cpufreq_target(..)
+         {
+                /* Do stuff like policy checks etc. */
+                /* Find the best frequency match for the req */
+                rcu_read_lock();
+                opp = opp_find_freq_ceil(dev, &freq);
+                rcu_read_unlock();
+                if (!IS_ERR(opp))
+                        soc_switch_to_freq_voltage(freq);
+                else
+                        /* do something when we cant satisfy the req */
+                /* do other stuff */
+         }
+
+4. OPP Availability Control Functions
+=====================================
+A default OPP list registered with the OPP library may not cater to all possible
+situation. The OPP library provides a set of functions to modify the
+availability of a OPP within the OPP list. This allows SoC frameworks to have
+fine grained dynamic control of which sets of OPPs are operationally available.
+These functions are intended to *temporarily* remove an OPP in conditions such
+as thermal considerations (e.g. don't use OPPx until the temperature drops).
+
+WARNING: Do not use these functions in interrupt context.
+
+opp_enable - Make a OPP available for operation.
+        Example: Lets say that 1GHz OPP is to be made available only if the
+        SoC temperature is lower than a certain threshold. The SoC framework
+        implementation might choose to do something as follows:
+         if (cur_temp < temp_low_thresh) {
+                /* Enable 1GHz if it was disabled */
+                rcu_read_lock();
+                opp = opp_find_freq_exact(dev, 1000000000, false);
+                rcu_read_unlock();
+                /* just error check */
+                if (!IS_ERR(opp))
+                        ret = opp_enable(dev, 1000000000);
+                else
+                        goto try_something_else;
+         }
+
+opp_disable - Make an OPP to be not available for operation
+        Example: Lets say that 1GHz OPP is to be disabled if the temperature
+        exceeds a threshold value. The SoC framework implementation might
+        choose to do something as follows:
+         if (cur_temp > temp_high_thresh) {
+                /* Disable 1GHz if it was enabled */
+                rcu_read_lock();
+                opp = opp_find_freq_exact(dev, 1000000000, true);
+                rcu_read_unlock();
+                /* just error check */
+                if (!IS_ERR(opp))
+                        ret = opp_disable(dev, 1000000000);
+                else
+                        goto try_something_else;
+         }
+
+5. OPP Data Retrieval Functions
+===============================
+Since OPP library abstracts away the OPP information, a set of functions to pull
+information from the OPP structure is necessary. Once an OPP pointer is
+retrieved using the search functions, the following functions can be used by SoC
+framework to retrieve the information represented inside the OPP layer.
+
+opp_get_voltage - Retrieve the voltage represented by the opp pointer.
+        Example: At a cpufreq transition to a different frequency, SoC
+        framework requires to set the voltage represented by the OPP using
+        the regulator framework to the Power Management chip providing the
+        voltage.
+         soc_switch_to_freq_voltage(freq)
+         {
+                /* do things */
+                rcu_read_lock();
+                opp = opp_find_freq_ceil(dev, &freq);
+                v = opp_get_voltage(opp);
+                rcu_read_unlock();
+                if (v)
+                        regulator_set_voltage(.., v);
+                /* do other things */
+         }
+
+opp_get_freq - Retrieve the freq represented by the opp pointer.
+        Example: Lets say the SoC framework uses a couple of helper functions
+        we could pass opp pointers instead of doing additional parameters to
+        handle quiet a bit of data parameters.
+         soc_cpufreq_target(..)
+         {
+                /* do things.. */
+                 max_freq = ULONG_MAX;
+                 rcu_read_lock();
+                 max_opp = opp_find_freq_floor(dev,&max_freq);
+                 requested_opp = opp_find_freq_ceil(dev,&freq);
+                 if (!IS_ERR(max_opp) && !IS_ERR(requested_opp))
+                        r = soc_test_validity(max_opp, requested_opp);
+                 rcu_read_unlock();
+                /* do other things */
+         }
+         soc_test_validity(..)
+         {
+                 if(opp_get_voltage(max_opp) < opp_get_voltage(requested_opp))
+                         return -EINVAL;
+                 if(opp_get_freq(max_opp) < opp_get_freq(requested_opp))
+                         return -EINVAL;
+                /* do things.. */
+         }
+
+opp_get_opp_count - Retrieve the number of available opps for a device
+        Example: Lets say a co-processor in the SoC needs to know the available
+        frequencies in a table, the main processor can notify as following:
+         soc_notify_coproc_available_frequencies()
+         {
+                /* Do things */
+                rcu_read_lock();
+                num_available = opp_get_opp_count(dev);
+                speeds = kzalloc(sizeof(u32) * num_available, GFP_KERNEL);
+                /* populate the table in increasing order */
+                freq = 0;
+                while (!IS_ERR(opp = opp_find_freq_ceil(dev, &freq))) {
+                        speeds[i] = freq;
+                        freq++;
+                        i++;
+                }
+                rcu_read_unlock();
+
+                soc_notify_coproc(AVAILABLE_FREQs, speeds, num_available);
+                /* Do other things */
+         }
+
+6. Cpufreq Table Generation
+===========================
+opp_init_cpufreq_table - cpufreq framework typically is initialized with
+        cpufreq_frequency_table_cpuinfo which is provided with the list of
+        frequencies that are available for operation. This function provides
+        a ready to use conversion routine to translate the OPP layer's internal
+        information about the available frequencies into a format readily
+        providable to cpufreq.
+
+        WARNING: Do not use this function in interrupt context.
+
+        Example:
+         soc_pm_init()
+         {
+                /* Do things */
+                r = opp_init_cpufreq_table(dev, &freq_table);
+                if (!r)
+                        cpufreq_frequency_table_cpuinfo(policy, freq_table);
+                /* Do other things */
+         }
+
+        NOTE: This function is available only if CONFIG_CPU_FREQ is enabled in
+        addition to CONFIG_PM as power management feature is required to
+        dynamically scale voltage and frequency in a system.
+
+7. Data Structures
+==================
+Typically an SoC contains multiple voltage domains which are variable. Each
+domain is represented by a device pointer. The relationship to OPP can be
+represented as follows:
+SoC
+ |- device 1
+ |      |- opp 1 (availability, freq, voltage)
+ |      |- opp 2 ..
+ ...    ...
+ |      `- opp n ..
+ |- device 2
+ ...
+ `- device m
+
+OPP library maintains a internal list that the SoC framework populates and
+accessed by various functions as described above. However, the structures
+representing the actual OPPs and domains are internal to the OPP library itself
+to allow for suitable abstraction reusable across systems.
+
+struct opp - The internal data structure of OPP library which is used to
+        represent an OPP. In addition to the freq, voltage, availability
+        information, it also contains internal book keeping information required
+        for the OPP library to operate on.  Pointer to this structure is
+        provided back to the users such as SoC framework to be used as a
+        identifier for OPP in the interactions with OPP layer.
+
+        WARNING: The struct opp pointer should not be parsed or modified by the
+        users. The defaults of for an instance is populated by opp_add, but the
+        availability of the OPP can be modified by opp_enable/disable functions.
+
+struct device - This is used to identify a domain to the OPP layer. The
+        nature of the device and it's implementation is left to the user of
+        OPP library such as the SoC framework.
+
+Overall, in a simplistic view, the data structure operations is represented as
+following:
+
+Initialization / modification:
+            +-----+        /- opp_enable
+opp_add --> | opp | <-------
+  |         +-----+        \- opp_disable
+  \-------> domain_info(device)
+
+Search functions:
+             /-- opp_find_freq_ceil  ---\   +-----+
+domain_info<---- opp_find_freq_exact -----> | opp |
+             \-- opp_find_freq_floor ---/   +-----+
+
+Retrieval functions:
++-----+     /- opp_get_voltage
+| opp | <---
++-----+     \- opp_get_freq
+
+domain_info <- opp_get_opp_count
diff --git a/drivers/base/power/Makefile b/drivers/base/power/Makefile
index cbccf9a3cee4..abe46edfe5b4 100644
--- a/drivers/base/power/Makefile
+++ b/drivers/base/power/Makefile
@@ -3,6 +3,7 @@ obj-$(CONFIG_PM_SLEEP)	+= main.o wakeup.o
 obj-$(CONFIG_PM_RUNTIME)        += runtime.o
 obj-$(CONFIG_PM_OPS)    += generic_ops.o
 obj-$(CONFIG_PM_TRACE_RTC)      += trace.o
+obj-$(CONFIG_PM_OPP)    += opp.o
 
 ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
 ccflags-$(CONFIG_PM_VERBOSE)   += -DDEBUG
diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
new file mode 100644
index 000000000000..2bb9b4cf59d7
--- /dev/null
+++ b/drivers/base/power/opp.c
@@ -0,0 +1,628 @@
+/*
+ * Generic OPP Interface
+ *
+ * Copyright (C) 2009-2010 Texas Instruments Incorporated.
+ *      Nishanth Menon
+ *      Romit Dasgupta
+ *      Kevin Hilman
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/cpufreq.h>
+#include <linux/list.h>
+#include <linux/rculist.h>
+#include <linux/rcupdate.h>
+#include <linux/opp.h>
+
+/*
+ * Internal data structure organization with the OPP layer library is as
+ * follows:
+ * dev_opp_list (root)
+ *      |- device 1 (represents voltage domain 1)
+ *      |       |- opp 1 (availability, freq, voltage)
+ *      |       |- opp 2 ..
+ *      ...     ...
+ *      |       `- opp n ..
+ *      |- device 2 (represents the next voltage domain)
+ *      ...
+ *      `- device m (represents mth voltage domain)
+ * device 1, 2.. are represented by dev_opp structure while each opp
+ * is represented by the opp structure.
+ */
+
+/**
+ * struct opp - Generic OPP description structure
+ * @node:       opp list node. The nodes are maintained throughout the lifetime
+ *              of boot. It is expected only an optimal set of OPPs are
+ *              added to the library by the SoC framework.
+ *              RCU usage: opp list is traversed with RCU locks. node
+ *              modification is possible realtime, hence the modifications
+ *              are protected by the dev_opp_list_lock for integrity.
+ *              IMPORTANT: the opp nodes should be maintained in increasing
+ *              order.
+ * @available:  true/false - marks if this OPP as available or not
+ * @rate:       Frequency in hertz
+ * @u_volt:     Nominal voltage in microvolts corresponding to this OPP
+ * @dev_opp:    points back to the device_opp struct this opp belongs to
+ *
+ * This structure stores the OPP information for a given device.
+ */
+struct opp {
+        struct list_head node;
+
+        bool available;
+        unsigned long rate;
+        unsigned long u_volt;
+
+        struct device_opp *dev_opp;
+};
+
+/**
+ * struct device_opp - Device opp structure
+ * @node:       list node - contains the devices with OPPs that
+ *              have been registered. Nodes once added are not modified in this
+ *              list.
+ *              RCU usage: nodes are not modified in the list of device_opp,
+ *              however addition is possible and is secured by dev_opp_list_lock
+ * @dev:        device pointer
+ * @opp_list:   list of opps
+ *
+ * This is an internal data structure maintaining the link to opps attached to
+ * a device. This structure is not meant to be shared to users as it is
+ * meant for book keeping and private to OPP library
+ */
+struct device_opp {
+        struct list_head node;
+
+        struct device *dev;
+        struct list_head opp_list;
+};
+
+/*
+ * The root of the list of all devices. All device_opp structures branch off
+ * from here, with each device_opp containing the list of opp it supports in
+ * various states of availability.
+ */
+static LIST_HEAD(dev_opp_list);
+/* Lock to allow exclusive modification to the device and opp lists */
+static DEFINE_MUTEX(dev_opp_list_lock);
+
+/**
+ * find_device_opp() - find device_opp struct using device pointer
+ * @dev:        device pointer used to lookup device OPPs
+ *
+ * Search list of device OPPs for one containing matching device. Does a RCU
+ * reader operation to grab the pointer needed.
+ *
+ * Returns pointer to 'struct device_opp' if found, otherwise -ENODEV or
+ * -EINVAL based on type of error.
+ *
+ * Locking: This function must be called under rcu_read_lock(). device_opp
+ * is a RCU protected pointer. This means that device_opp is valid as long
+ * as we are under RCU lock.
+ */
+static struct device_opp *find_device_opp(struct device *dev)
+{
+        struct device_opp *tmp_dev_opp, *dev_opp = ERR_PTR(-ENODEV);
+
+        if (unlikely(IS_ERR_OR_NULL(dev))) {
+                pr_err("%s: Invalid parameters\n", __func__);
+                return ERR_PTR(-EINVAL);
+        }
+
+        list_for_each_entry_rcu(tmp_dev_opp, &dev_opp_list, node) {
+                if (tmp_dev_opp->dev == dev) {
+                        dev_opp = tmp_dev_opp;
+                        break;
+                }
+        }
+
+        return dev_opp;
+}
+
+/**
+ * opp_get_voltage() - Gets the voltage corresponding to an available opp
+ * @opp:        opp for which voltage has to be returned for
+ *
+ * Return voltage in micro volt corresponding to the opp, else
+ * return 0
+ *
+ * Locking: This function must be called under rcu_read_lock(). opp is a rcu
+ * protected pointer. This means that opp which could have been fetched by
+ * opp_find_freq_{exact,ceil,floor} functions is valid as long as we are
+ * under RCU lock. The pointer returned by the opp_find_freq family must be
+ * used in the same section as the usage of this function with the pointer
+ * prior to unlocking with rcu_read_unlock() to maintain the integrity of the
+ * pointer.
+ */
+unsigned long opp_get_voltage(struct opp *opp)
+{
+        struct opp *tmp_opp;
+        unsigned long v = 0;
+
+        tmp_opp = rcu_dereference(opp);
+        if (unlikely(IS_ERR_OR_NULL(tmp_opp)) || !tmp_opp->available)
+                pr_err("%s: Invalid parameters\n", __func__);
+        else
+                v = tmp_opp->u_volt;
+
+        return v;
+}
+
+/**
+ * opp_get_freq() - Gets the frequency corresponding to an available opp
+ * @opp:        opp for which frequency has to be returned for
+ *
+ * Return frequency in hertz corresponding to the opp, else
+ * return 0
+ *
+ * Locking: This function must be called under rcu_read_lock(). opp is a rcu
+ * protected pointer. This means that opp which could have been fetched by
+ * opp_find_freq_{exact,ceil,floor} functions is valid as long as we are
+ * under RCU lock. The pointer returned by the opp_find_freq family must be
+ * used in the same section as the usage of this function with the pointer
+ * prior to unlocking with rcu_read_unlock() to maintain the integrity of the
+ * pointer.
+ */
+unsigned long opp_get_freq(struct opp *opp)
+{
+        struct opp *tmp_opp;
+        unsigned long f = 0;
+
+        tmp_opp = rcu_dereference(opp);
+        if (unlikely(IS_ERR_OR_NULL(tmp_opp)) || !tmp_opp->available)
+                pr_err("%s: Invalid parameters\n", __func__);
+        else
+                f = tmp_opp->rate;
+
+        return f;
+}
+
+/**
+ * opp_get_opp_count() - Get number of opps available in the opp list
+ * @dev:        device for which we do this operation
+ *
+ * This function returns the number of available opps if there are any,
+ * else returns 0 if none or the corresponding error value.
+ *
+ * Locking: This function must be called under rcu_read_lock(). This function
+ * internally references two RCU protected structures: device_opp and opp which
+ * are safe as long as we are under a common RCU locked section.
+ */
+int opp_get_opp_count(struct device *dev)
+{
+        struct device_opp *dev_opp;
+        struct opp *temp_opp;
+        int count = 0;
+
+        dev_opp = find_device_opp(dev);
+        if (IS_ERR(dev_opp)) {
+                int r = PTR_ERR(dev_opp);
+                dev_err(dev, "%s: device OPP not found (%d)\n", __func__, r);
+                return r;
+        }
+
+        list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) {
+                if (temp_opp->available)
+                        count++;
+        }
+
+        return count;
+}
+
+/**
+ * opp_find_freq_exact() - search for an exact frequency
+ * @dev:                device for which we do this operation
+ * @freq:               frequency to search for
+ * @is_available:       true/false - match for available opp
+ *
+ * Searches for exact match in the opp list and returns pointer to the matching
+ * opp if found, else returns ERR_PTR in case of error and should be handled
+ * using IS_ERR.
+ *
+ * Note: available is a modifier for the search. if available=true, then the
+ * match is for exact matching frequency and is available in the stored OPP
+ * table. if false, the match is for exact frequency which is not available.
+ *
+ * This provides a mechanism to enable an opp which is not available currently
+ * or the opposite as well.
+ *
+ * Locking: This function must be called under rcu_read_lock(). opp is a rcu
+ * protected pointer. The reason for the same is that the opp pointer which is
+ * returned will remain valid for use with opp_get_{voltage, freq} only while
+ * under the locked area. The pointer returned must be used prior to unlocking
+ * with rcu_read_unlock() to maintain the integrity of the pointer.
+ */
+struct opp *opp_find_freq_exact(struct device *dev, unsigned long freq,
+                                bool available)
+{
+        struct device_opp *dev_opp;
+        struct opp *temp_opp, *opp = ERR_PTR(-ENODEV);
+
+        dev_opp = find_device_opp(dev);
+        if (IS_ERR(dev_opp)) {
+                int r = PTR_ERR(dev_opp);
+                dev_err(dev, "%s: device OPP not found (%d)\n", __func__, r);
+                return ERR_PTR(r);
+        }
+
+        list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) {
+                if (temp_opp->available == available &&
+                                temp_opp->rate == freq) {
+                        opp = temp_opp;
+                        break;
+                }
+        }
+
+        return opp;
+}
+
+/**
+ * opp_find_freq_ceil() - Search for an rounded ceil freq
+ * @dev:        device for which we do this operation
+ * @freq:       Start frequency
+ *
+ * Search for the matching ceil *available* OPP from a starting freq
+ * for a device.
+ *
+ * Returns matching *opp and refreshes *freq accordingly, else returns
+ * ERR_PTR in case of error and should be handled using IS_ERR.
+ *
+ * Locking: This function must be called under rcu_read_lock(). opp is a rcu
+ * protected pointer. The reason for the same is that the opp pointer which is
+ * returned will remain valid for use with opp_get_{voltage, freq} only while
+ * under the locked area. The pointer returned must be used prior to unlocking
+ * with rcu_read_unlock() to maintain the integrity of the pointer.
+ */
+struct opp *opp_find_freq_ceil(struct device *dev, unsigned long *freq)
+{
+        struct device_opp *dev_opp;
+        struct opp *temp_opp, *opp = ERR_PTR(-ENODEV);
+
+        if (!dev || !freq) {
+                dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq);
+                return ERR_PTR(-EINVAL);
+        }
+
+        dev_opp = find_device_opp(dev);
+        if (IS_ERR(dev_opp))
+                return opp;
+
+        list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) {
+                if (temp_opp->available && temp_opp->rate >= *freq) {
+                        opp = temp_opp;
+                        *freq = opp->rate;
+                        break;
+                }
+        }
+
+        return opp;
+}
+
+/**
+ * opp_find_freq_floor() - Search for a rounded floor freq
+ * @dev:        device for which we do this operation
+ * @freq:       Start frequency
+ *
+ * Search for the matching floor *available* OPP from a starting freq
+ * for a device.
+ *
+ * Returns matching *opp and refreshes *freq accordingly, else returns
+ * ERR_PTR in case of error and should be handled using IS_ERR.
+ *
+ * Locking: This function must be called under rcu_read_lock(). opp is a rcu
+ * protected pointer. The reason for the same is that the opp pointer which is
+ * returned will remain valid for use with opp_get_{voltage, freq} only while
+ * under the locked area. The pointer returned must be used prior to unlocking
+ * with rcu_read_unlock() to maintain the integrity of the pointer.
+ */
+struct opp *opp_find_freq_floor(struct device *dev, unsigned long *freq)
+{
+        struct device_opp *dev_opp;
+        struct opp *temp_opp, *opp = ERR_PTR(-ENODEV);
+
+        if (!dev || !freq) {
+                dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq);
+                return ERR_PTR(-EINVAL);
+        }
+
+        dev_opp = find_device_opp(dev);
+        if (IS_ERR(dev_opp))
+                return opp;
+
+        list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) {
+                if (temp_opp->available) {
+                        /* go to the next node, before choosing prev */
+                        if (temp_opp->rate > *freq)
+                                break;
+                        else
+                                opp = temp_opp;
+                }
+        }
+        if (!IS_ERR(opp))
+                *freq = opp->rate;
+
+        return opp;
+}
+
+/**
+ * opp_add()  - Add an OPP table from a table definitions
+ * @dev:        device for which we do this operation
+ * @freq:       Frequency in Hz for this OPP
+ * @u_volt:     Voltage in uVolts for this OPP
+ *
+ * This function adds an opp definition to the opp list and returns status.
+ * The opp is made available by default and it can be controlled using
+ * opp_enable/disable functions.
+ *
+ * Locking: The internal device_opp and opp structures are RCU protected.
+ * Hence this function internally uses RCU updater strategy with mutex locks
+ * to keep the integrity of the internal data structures. Callers should ensure
+ * that this function is *NOT* called under RCU protection or in contexts where
+ * mutex cannot be locked.
+ */
+int opp_add(struct device *dev, unsigned long freq, unsigned long u_volt)
+{
+        struct device_opp *dev_opp = NULL;
+        struct opp *opp, *new_opp;
+        struct list_head *head;
+
+        /* allocate new OPP node */
+        new_opp = kzalloc(sizeof(struct opp), GFP_KERNEL);
+        if (!new_opp) {
+                dev_warn(dev, "%s: Unable to create new OPP node\n", __func__);
+                return -ENOMEM;
+        }
+
+        /* Hold our list modification lock here */
+        mutex_lock(&dev_opp_list_lock);
+
+        /* Check for existing list for 'dev' */
+        dev_opp = find_device_opp(dev);
+        if (IS_ERR(dev_opp)) {
+                /*
+                 * Allocate a new device OPP table. In the infrequent case
+                 * where a new device is needed to be added, we pay this
+                 * penalty.
+                 */
+                dev_opp = kzalloc(sizeof(struct device_opp), GFP_KERNEL);
+                if (!dev_opp) {
+                        mutex_unlock(&dev_opp_list_lock);
+                        kfree(new_opp);
+                        dev_warn(dev,
+                                "%s: Unable to create device OPP structure\n",
+                                __func__);
+                        return -ENOMEM;
+                }
+
+                dev_opp->dev = dev;
+                INIT_LIST_HEAD(&dev_opp->opp_list);
+
+                /* Secure the device list modification */
+                list_add_rcu(&dev_opp->node, &dev_opp_list);
+        }
+
+        /* populate the opp table */
+        new_opp->dev_opp = dev_opp;
+        new_opp->rate = freq;
+        new_opp->u_volt = u_volt;
+        new_opp->available = true;
+
+        /* Insert new OPP in order of increasing frequency */
+        head = &dev_opp->opp_list;
+        list_for_each_entry_rcu(opp, &dev_opp->opp_list, node) {
+                if (new_opp->rate < opp->rate)
+                        break;
+                else
+                        head = &opp->node;
+        }
+
+        list_add_rcu(&new_opp->node, head);
+        mutex_unlock(&dev_opp_list_lock);
+
+        return 0;
+}
+
+/**
+ * opp_set_availability() - helper to set the availability of an opp
+ * @dev:                device for which we do this operation
+ * @freq:               OPP frequency to modify availability
+ * @availability_req:   availability status requested for this opp
+ *
+ * Set the availability of an OPP with an RCU operation, opp_{enable,disable}
+ * share a common logic which is isolated here.
+ *
+ * Returns -EINVAL for bad pointers, -ENOMEM if no memory available for the
+ * copy operation, returns 0 if no modifcation was done OR modification was
+ * successful.
+ *
+ * Locking: The internal device_opp and opp structures are RCU protected.
+ * Hence this function internally uses RCU updater strategy with mutex locks to
+ * keep the integrity of the internal data structures. Callers should ensure
+ * that this function is *NOT* called under RCU protection or in contexts where
+ * mutex locking or synchronize_rcu() blocking calls cannot be used.
+ */
+static int opp_set_availability(struct device *dev, unsigned long freq,
+                bool availability_req)
+{
+        struct device_opp *tmp_dev_opp, *dev_opp = NULL;
+        struct opp *new_opp, *tmp_opp, *opp = ERR_PTR(-ENODEV);
+        int r = 0;
+
+        /* keep the node allocated */
+        new_opp = kmalloc(sizeof(struct opp), GFP_KERNEL);
+        if (!new_opp) {
+                dev_warn(dev, "%s: Unable to create OPP\n", __func__);
+                return -ENOMEM;
+        }
+
+        mutex_lock(&dev_opp_list_lock);
+
+        /* Find the device_opp */
+        list_for_each_entry(tmp_dev_opp, &dev_opp_list, node) {
+                if (dev == tmp_dev_opp->dev) {
+                        dev_opp = tmp_dev_opp;
+                        break;
+                }
+        }
+        if (IS_ERR(dev_opp)) {
+                r = PTR_ERR(dev_opp);
+                dev_warn(dev, "%s: Device OPP not found (%d)\n", __func__, r);
+                goto unlock;
+        }
+
+        /* Do we have the frequency? */
+        list_for_each_entry(tmp_opp, &dev_opp->opp_list, node) {
+                if (tmp_opp->rate == freq) {
+                        opp = tmp_opp;
+                        break;
+                }
+        }
+        if (IS_ERR(opp)) {
+                r = PTR_ERR(opp);
+                goto unlock;
+        }
+
+        /* Is update really needed? */
+        if (opp->available == availability_req)
+                goto unlock;
+        /* copy the old data over */
+        *new_opp = *opp;
+
+        /* plug in new node */
+        new_opp->available = availability_req;
+
+        list_replace_rcu(&opp->node, &new_opp->node);
+        mutex_unlock(&dev_opp_list_lock);
+        synchronize_rcu();
+
+        /* clean up old opp */
+        new_opp = opp;
+        goto out;
+
+unlock:
+        mutex_unlock(&dev_opp_list_lock);
+out:
+        kfree(new_opp);
+        return r;
+}
+
+/**
+ * opp_enable() - Enable a specific OPP
+ * @dev:        device for which we do this operation
+ * @freq:       OPP frequency to enable
+ *
+ * Enables a provided opp. If the operation is valid, this returns 0, else the
+ * corresponding error value. It is meant to be used for users an OPP available
+ * after being temporarily made unavailable with opp_disable.
+ *
+ * Locking: The internal device_opp and opp structures are RCU protected.
+ * Hence this function indirectly uses RCU and mutex locks to keep the
+ * integrity of the internal data structures. Callers should ensure that
+ * this function is *NOT* called under RCU protection or in contexts where
+ * mutex locking or synchronize_rcu() blocking calls cannot be used.
+ */
+int opp_enable(struct device *dev, unsigned long freq)
+{
+        return opp_set_availability(dev, freq, true);
+}
+
+/**
+ * opp_disable() - Disable a specific OPP
+ * @dev:        device for which we do this operation
+ * @freq:       OPP frequency to disable
+ *
+ * Disables a provided opp. If the operation is valid, this returns
+ * 0, else the corresponding error value. It is meant to be a temporary
+ * control by users to make this OPP not available until the circumstances are
+ * right to make it available again (with a call to opp_enable).
+ *
+ * Locking: The internal device_opp and opp structures are RCU protected.
+ * Hence this function indirectly uses RCU and mutex locks to keep the
+ * integrity of the internal data structures. Callers should ensure that
+ * this function is *NOT* called under RCU protection or in contexts where
+ * mutex locking or synchronize_rcu() blocking calls cannot be used.
+ */
+int opp_disable(struct device *dev, unsigned long freq)
+{
+        return opp_set_availability(dev, freq, false);
+}
+
+#ifdef CONFIG_CPU_FREQ
+/**
+ * opp_init_cpufreq_table() - create a cpufreq table for a device
+ * @dev:        device for which we do this operation
+ * @table:      Cpufreq table returned back to caller
+ *
+ * Generate a cpufreq table for a provided device- this assumes that the
+ * opp list is already initialized and ready for usage.
+ *
+ * This function allocates required memory for the cpufreq table. It is
+ * expected that the caller does the required maintenance such as freeing
+ * the table as required.
+ *
+ * Returns -EINVAL for bad pointers, -ENODEV if the device is not found, -ENOMEM
+ * if no memory available for the operation (table is not populated), returns 0
+ * if successful and table is populated.
+ *
+ * WARNING: It is  important for the callers to ensure refreshing their copy of
+ * the table if any of the mentioned functions have been invoked in the interim.
+ *
+ * Locking: The internal device_opp and opp structures are RCU protected.
+ * To simplify the logic, we pretend we are updater and hold relevant mutex here
+ * Callers should ensure that this function is *NOT* called under RCU protection
+ * or in contexts where mutex locking cannot be used.
+ */
+int opp_init_cpufreq_table(struct device *dev,
+                            struct cpufreq_frequency_table **table)
+{
+        struct device_opp *dev_opp;
+        struct opp *opp;
+        struct cpufreq_frequency_table *freq_table;
+        int i = 0;
+
+        /* Pretend as if I am an updater */
+        mutex_lock(&dev_opp_list_lock);
+
+        dev_opp = find_device_opp(dev);
+        if (IS_ERR(dev_opp)) {
+                int r = PTR_ERR(dev_opp);
+                mutex_unlock(&dev_opp_list_lock);
+                dev_err(dev, "%s: Device OPP not found (%d)\n", __func__, r);
+                return r;
+        }
+
+        freq_table = kzalloc(sizeof(struct cpufreq_frequency_table) *
+                             (opp_get_opp_count(dev) + 1), GFP_KERNEL);
+        if (!freq_table) {
+                mutex_unlock(&dev_opp_list_lock);
+                dev_warn(dev, "%s: Unable to allocate frequency table\n",
+                        __func__);
+                return -ENOMEM;
+        }
+
+        list_for_each_entry(opp, &dev_opp->opp_list, node) {
+                if (opp->available) {
+                        freq_table[i].index = i;
+                        freq_table[i].frequency = opp->rate / 1000;
+                        i++;
+                }
+        }
+        mutex_unlock(&dev_opp_list_lock);
+
+        freq_table[i].index = i;
+        freq_table[i].frequency = CPUFREQ_TABLE_END;
+
+        *table = &freq_table[0];
+
+        return 0;
+}
+#endif          /* CONFIG_CPU_FREQ */
diff --git a/include/linux/opp.h b/include/linux/opp.h
new file mode 100644
index 000000000000..5449945d589f
--- /dev/null
+++ b/include/linux/opp.h
@@ -0,0 +1,105 @@
+/*
+ * Generic OPP Interface
+ *
+ * Copyright (C) 2009-2010 Texas Instruments Incorporated.
+ *      Nishanth Menon
+ *      Romit Dasgupta
+ *      Kevin Hilman
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __LINUX_OPP_H__
+#define __LINUX_OPP_H__
+
+#include <linux/err.h>
+#include <linux/cpufreq.h>
+
+struct opp;
+
+#if defined(CONFIG_PM_OPP)
+
+unsigned long opp_get_voltage(struct opp *opp);
+
+unsigned long opp_get_freq(struct opp *opp);
+
+int opp_get_opp_count(struct device *dev);
+
+struct opp *opp_find_freq_exact(struct device *dev, unsigned long freq,
+                                bool available);
+
+struct opp *opp_find_freq_floor(struct device *dev, unsigned long *freq);
+
+struct opp *opp_find_freq_ceil(struct device *dev, unsigned long *freq);
+
+int opp_add(struct device *dev, unsigned long freq, unsigned long u_volt);
+
+int opp_enable(struct device *dev, unsigned long freq);
+
+int opp_disable(struct device *dev, unsigned long freq);
+
+#else
+static inline unsigned long opp_get_voltage(struct opp *opp)
+{
+        return 0;
+}
+
+static inline unsigned long opp_get_freq(struct opp *opp)
+{
+        return 0;
+}
+
+static inline int opp_get_opp_count(struct device *dev)
+{
+        return 0;
+}
+
+static inline struct opp *opp_find_freq_exact(struct device *dev,
+                                        unsigned long freq, bool available)
+{
+        return ERR_PTR(-EINVAL);
+}
+
+static inline struct opp *opp_find_freq_floor(struct device *dev,
+                                        unsigned long *freq)
+{
+        return ERR_PTR(-EINVAL);
+}
+
+static inline struct opp *opp_find_freq_ceil(struct device *dev,
+                                        unsigned long *freq)
+{
+        return ERR_PTR(-EINVAL);
+}
+
+static inline int opp_add(struct device *dev, unsigned long freq,
+                                        unsigned long u_volt)
+{
+        return -EINVAL;
+}
+
+static inline int opp_enable(struct device *dev, unsigned long freq)
+{
+        return 0;
+}
+
+static inline int opp_disable(struct device *dev, unsigned long freq)
+{
+        return 0;
+}
+#endif          /* CONFIG_PM */
+
+#if defined(CONFIG_CPU_FREQ) && defined(CONFIG_PM_OPP)
+int opp_init_cpufreq_table(struct device *dev,
+                            struct cpufreq_frequency_table **table);
+#else
+static inline int opp_init_cpufreq_table(struct device *dev,
+                            struct cpufreq_frequency_table **table)
+{
+        return -EINVAL;
+}
+#endif          /* CONFIG_CPU_FREQ */
+
+#endif          /* __LINUX_OPP_H__ */
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index e45894c696ee..29bff6117abc 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -245,3 +245,17 @@ config PM_OPS
         bool
         depends on PM_SLEEP || PM_RUNTIME
         default y
+
+config PM_OPP
+        bool "Operating Performance Point (OPP) Layer library"
+        depends on PM
+        ---help---
+          SOCs have a standard set of tuples consisting of frequency and
+          voltage pairs that the device will support per voltage domain. This
+          is called Operating Performance Point or OPP. The actual definitions
+          of OPP varies over silicon within the same family of devices.
+
+          OPP layer organizes the data internally using device pointers
+          representing individual voltage domains and provides SOC
+          implementations a ready to use framework to manage OPPs.
+          For more information, read <file:Documentation/power/opp.txt>