drivers/base/power/opp/opp.h

/*
 * 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 __DRIVER_OPP_H__
#define __DRIVER_OPP_H__

#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/pm_opp.h>
#include <linux/rculist.h>
#include <linux/rcupdate.h>

/* Lock to allow exclusive modification to the device and opp lists */
extern struct mutex dev_opp_list_lock;

/*
 * 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 dev_pm_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.
 * @dynamic:	not-created from static DT entries.
 * @available:	true/false - marks if this OPP as available or not
 * @turbo:	true if turbo (boost) OPP
 * @rate:	Frequency in hertz
 * @u_volt:	Target voltage in microvolts corresponding to this OPP
 * @u_volt_min:	Minimum voltage in microvolts corresponding to this OPP
 * @u_volt_max:	Maximum voltage in microvolts corresponding to this OPP
 * @u_amp:	Maximum current drawn by the device in microamperes
 * @clock_latency_ns: Latency (in nanoseconds) of switching to this OPP's
 *		frequency from any other OPP's frequency.
 * @dev_opp:	points back to the device_opp struct this opp belongs to
 * @rcu_head:	RCU callback head used for deferred freeing
 * @np:		OPP's device node.
 *
 * This structure stores the OPP information for a given device.
 */
struct dev_pm_opp {
	struct list_head node;

	bool available;
	bool dynamic;
	bool turbo;
	unsigned long rate;

	unsigned long u_volt;
	unsigned long u_volt_min;
	unsigned long u_volt_max;
	unsigned long u_amp;
	unsigned long clock_latency_ns;

	struct device_opp *dev_opp;
	struct rcu_head rcu_head;

	struct device_node *np;
};

/**
 * struct device_list_opp - devices managed by 'struct device_opp'
 * @node:	list node
 * @dev:	device to which the struct object belongs
 * @rcu_head:	RCU callback head used for deferred freeing
 *
 * This is an internal data structure maintaining the list of devices that are
 * managed by 'struct device_opp'.
 */
struct device_list_opp {
	struct list_head node;
	const struct device *dev;
	struct rcu_head rcu_head;
};

/**
 * 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
 * @srcu_head:	notifier head to notify the OPP availability changes.
 * @rcu_head:	RCU callback head used for deferred freeing
 * @dev_list:	list of devices that share these OPPs
 * @opp_list:	list of opps
 * @np:		struct device_node pointer for opp's DT node.
 * @shared_opp: OPP is shared between multiple devices.
 *
 * 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.
 *
 * Because the opp structures can be used from both rcu and srcu readers, we
 * need to wait for the grace period of both of them before freeing any
 * resources. And so we have used kfree_rcu() from within call_srcu() handlers.
 */
struct device_opp {
	struct list_head node;

	struct srcu_notifier_head srcu_head;
	struct rcu_head rcu_head;
	struct list_head dev_list;
	struct list_head opp_list;

	struct device_node *np;
	unsigned long clock_latency_ns_max;
	bool shared_opp;
	struct dev_pm_opp *suspend_opp;
};

/* Routines internal to opp core */
struct device_opp *_find_device_opp(struct device *dev);
struct device_list_opp *_add_list_dev(const struct device *dev,
				      struct device_opp *dev_opp);
struct device_node *_of_get_opp_desc_node(struct device *dev);

#endif		/* __DRIVER_OPP_H__ */