/*
* 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
* @head: notifier head to notify the OPP availability changes.
* @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 srcu_notifier_head head;
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
* @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;
srcu_init_notifier_head(&dev_opp->head);
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);
/*
* Notify the changes in the availability of the operable
* frequency/voltage list.
*/
srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_ADD, new_opp);
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 = ERR_PTR(-ENODEV);
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();
/* Notify the change of the OPP availability */
if (availability_req)
srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_ENABLE,
new_opp);
else
srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_DISABLE,
new_opp);
/* 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;
}
/**
* opp_free_cpufreq_table() - free the cpufreq table
* @dev: device for which we do this operation
* @table: table to free
*
* Free up the table allocated by opp_init_cpufreq_table
*/
void opp_free_cpufreq_table(struct device *dev,
struct cpufreq_frequency_table **table)
{
if (!table)
return;
kfree(*table);
*table = NULL;
}
#endif /* CONFIG_CPU_FREQ */
/**
* opp_get_notifier() - find notifier_head of the device with opp
* @dev: device pointer used to lookup device OPPs.
*/
struct srcu_notifier_head *opp_get_notifier(struct device *dev)
{
struct device_opp *dev_opp = find_device_opp(dev);
if (IS_ERR(dev_opp))
return ERR_PTR(PTR_ERR(dev_opp)); /* matching type */
return &dev_opp->head;
}
