/*
   *  linux/drivers/thermal/cpu_cooling.c
   *
   *  Copyright (C) 2012	Samsung Electronics Co., Ltd(http://www.samsung.com)
   *  Copyright (C) 2012  Amit Daniel <amit.kachhap@linaro.org>
   *
   * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   *  This program is free software; you can redistribute it and/or modify
   *  it under the terms of the GNU General Public License as published by
   *  the Free Software Foundation; version 2 of the License.
   *
   *  This program is distributed in the hope that it will be useful, but
   *  WITHOUT ANY WARRANTY; without even the implied warranty of
   *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   *  General Public License for more details.
   *
   *  You should have received a copy of the GNU General Public License along
   *  with this program; if not, write to the Free Software Foundation, Inc.,
   *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
   *
   * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   */
  #include <linux/module.h>
  #include <linux/thermal.h>
  #include <linux/cpufreq.h>
  #include <linux/err.h>
  #include <linux/slab.h>
  #include <linux/cpu.h>
  #include <linux/cpu_cooling.h>
  
  /**
   * struct cpufreq_cooling_device - data for cooling device with cpufreq
   * @id: unique integer value corresponding to each cpufreq_cooling_device
   *	registered.
   * @cool_dev: thermal_cooling_device pointer to keep track of the
   *	registered cooling device.
   * @cpufreq_state: integer value representing the current state of cpufreq
   *	cooling	devices.
   * @cpufreq_val: integer value representing the absolute value of the clipped
   *	frequency.
   * @allowed_cpus: all the cpus involved for this cpufreq_cooling_device.
   *
   * This structure is required for keeping information of each
   * cpufreq_cooling_device registered. In order to prevent corruption of this a
   * mutex lock cooling_cpufreq_lock is used.
   */
  struct cpufreq_cooling_device {
  	int id;
  	struct thermal_cooling_device *cool_dev;
  	unsigned int cpufreq_state;
  	unsigned int cpufreq_val;
  	struct cpumask allowed_cpus;
  };
  static DEFINE_IDR(cpufreq_idr);
  static DEFINE_MUTEX(cooling_cpufreq_lock);
  
  static unsigned int cpufreq_dev_count;
  
  /* notify_table passes value to the CPUFREQ_ADJUST callback function. */
  #define NOTIFY_INVALID NULL
  static struct cpufreq_cooling_device *notify_device;
  
  /**
   * get_idr - function to get a unique id.
   * @idr: struct idr * handle used to create a id.
   * @id: int * value generated by this function.
   *
   * This function will populate @id with an unique
   * id, using the idr API.
   *
   * Return: 0 on success, an error code on failure.
   */
  static int get_idr(struct idr *idr, int *id)
  {
  	int ret;
  
  	mutex_lock(&cooling_cpufreq_lock);
  	ret = idr_alloc(idr, NULL, 0, 0, GFP_KERNEL);
  	mutex_unlock(&cooling_cpufreq_lock);
  	if (unlikely(ret < 0))
  		return ret;
  	*id = ret;
  
  	return 0;
  }
  
  /**
   * release_idr - function to free the unique id.
   * @idr: struct idr * handle used for creating the id.
   * @id: int value representing the unique id.
   */
  static void release_idr(struct idr *idr, int id)
  {
  	mutex_lock(&cooling_cpufreq_lock);
  	idr_remove(idr, id);
  	mutex_unlock(&cooling_cpufreq_lock);
  }
  
  /* Below code defines functions to be used for cpufreq as cooling device */
  
  /**
   * is_cpufreq_valid - function to check frequency transitioning capability.
   * @cpu: cpu for which check is needed.
   *
   * This function will check the current state of the system if
   * it is capable of changing the frequency for a given @cpu.
   *
   * Return: 0 if the system is not currently capable of changing
   * the frequency of given cpu. !0 in case the frequency is changeable.
   */
  static int is_cpufreq_valid(int cpu)
  {
  	struct cpufreq_policy policy;
  
  	return !cpufreq_get_policy(&policy, cpu);
  }
  
  enum cpufreq_cooling_property {
  	GET_LEVEL,
  	GET_FREQ,
  	GET_MAXL,
  };
  
  /**
   * get_property - fetch a property of interest for a give cpu.
   * @cpu: cpu for which the property is required
   * @input: query parameter
   * @output: query return
   * @property: type of query (frequency, level, max level)
   *
   * This is the common function to
   * 1. get maximum cpu cooling states
   * 2. translate frequency to cooling state
   * 3. translate cooling state to frequency
   * Note that the code may be not in good shape
   * but it is written in this way in order to:
   * a) reduce duplicate code as most of the code can be shared.
   * b) make sure the logic is consistent when translating between
   *    cooling states and frequencies.
   *
   * Return: 0 on success, -EINVAL when invalid parameters are passed.
   */
  static int get_property(unsigned int cpu, unsigned long input,
  			unsigned int *output,
  			enum cpufreq_cooling_property property)
  {
  	int i, j;
  	unsigned long max_level = 0, level = 0;
  	unsigned int freq = CPUFREQ_ENTRY_INVALID;
  	int descend = -1;
  	struct cpufreq_frequency_table *table =
  					cpufreq_frequency_get_table(cpu);
  
  	if (!output)
  		return -EINVAL;
  
  	if (!table)
  		return -EINVAL;
  
  	for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
  		/* ignore invalid entries */
  		if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
  			continue;
  
  		/* ignore duplicate entry */
  		if (freq == table[i].frequency)
  			continue;
  
  		/* get the frequency order */
  		if (freq != CPUFREQ_ENTRY_INVALID && descend == -1)
  			descend = !!(freq > table[i].frequency);
  
  		freq = table[i].frequency;
  		max_level++;
  	}
  
  	/* No valid cpu frequency entry */
  	if (max_level == 0)
  		return -EINVAL;
  
  	/* max_level is an index, not a counter */
  	max_level--;
  
  	/* get max level */
  	if (property == GET_MAXL) {
  		*output = (unsigned int)max_level;
  		return 0;
  	}
  
  	if (property == GET_FREQ)
  		level = descend ? input : (max_level - input);
  
  	for (i = 0, j = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
  		/* ignore invalid entry */
  		if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
  			continue;
  
  		/* ignore duplicate entry */
  		if (freq == table[i].frequency)
  			continue;
  
  		/* now we have a valid frequency entry */
  		freq = table[i].frequency;
  
  		if (property == GET_LEVEL && (unsigned int)input == freq) {
  			/* get level by frequency */
  			*output = descend ? j : (max_level - j);
  			return 0;
  		}
  		if (property == GET_FREQ && level == j) {
  			/* get frequency by level */
  			*output = freq;
  			return 0;
  		}
  		j++;
  	}
  
  	return -EINVAL;
  }
  
  /**
   * cpufreq_cooling_get_level - for a give cpu, return the cooling level.
   * @cpu: cpu for which the level is required
   * @freq: the frequency of interest
   *
   * This function will match the cooling level corresponding to the
   * requested @freq and return it.
   *
   * Return: The matched cooling level on success or THERMAL_CSTATE_INVALID
   * otherwise.
   */
  unsigned long cpufreq_cooling_get_level(unsigned int cpu, unsigned int freq)
  {
  	unsigned int val;
  
  	if (get_property(cpu, (unsigned long)freq, &val, GET_LEVEL))
  		return THERMAL_CSTATE_INVALID;
  
  	return (unsigned long)val;
  }
  EXPORT_SYMBOL_GPL(cpufreq_cooling_get_level);
  
  /**
   * get_cpu_frequency - get the absolute value of frequency from level.
   * @cpu: cpu for which frequency is fetched.
   * @level: cooling level
   *
   * This function matches cooling level with frequency. Based on a cooling level
   * of frequency, equals cooling state of cpu cooling device, it will return
   * the corresponding frequency.
   *	e.g level=0 --> 1st MAX FREQ, level=1 ---> 2nd MAX FREQ, .... etc
   *
   * Return: 0 on error, the corresponding frequency otherwise.
   */
  static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
  {
  	int ret = 0;
  	unsigned int freq;
  
  	ret = get_property(cpu, level, &freq, GET_FREQ);
  	if (ret)
  		return 0;
  
  	return freq;
  }
  
  /**
   * cpufreq_apply_cooling - function to apply frequency clipping.
   * @cpufreq_device: cpufreq_cooling_device pointer containing frequency
   *	clipping data.
   * @cooling_state: value of the cooling state.
   *
   * Function used to make sure the cpufreq layer is aware of current thermal
   * limits. The limits are applied by updating the cpufreq policy.
   *
   * Return: 0 on success, an error code otherwise (-EINVAL in case wrong
   * cooling state).
   */
  static int cpufreq_apply_cooling(struct cpufreq_cooling_device *cpufreq_device,
  				 unsigned long cooling_state)
  {
  	unsigned int cpuid, clip_freq;
  	struct cpumask *mask = &cpufreq_device->allowed_cpus;
  	unsigned int cpu = cpumask_any(mask);
  
  
  	/* Check if the old cooling action is same as new cooling action */
  	if (cpufreq_device->cpufreq_state == cooling_state)
  		return 0;
  
  	clip_freq = get_cpu_frequency(cpu, cooling_state);
  	if (!clip_freq)
  		return -EINVAL;
  
  	cpufreq_device->cpufreq_state = cooling_state;
  	cpufreq_device->cpufreq_val = clip_freq;
  	notify_device = cpufreq_device;
  
  	for_each_cpu(cpuid, mask) {
  		if (is_cpufreq_valid(cpuid))
  			cpufreq_update_policy(cpuid);
  	}
  
  	notify_device = NOTIFY_INVALID;
  
  	return 0;
  }
  
  /**
   * cpufreq_thermal_notifier - notifier callback for cpufreq policy change.
   * @nb:	struct notifier_block * with callback info.
   * @event: value showing cpufreq event for which this function invoked.
   * @data: callback-specific data
   *
   * Callback to highjack the notification on cpufreq policy transition.
   * Every time there is a change in policy, we will intercept and
   * update the cpufreq policy with thermal constraints.
   *
   * Return: 0 (success)
   */
  static int cpufreq_thermal_notifier(struct notifier_block *nb,
  				    unsigned long event, void *data)
  {
  	struct cpufreq_policy *policy = data;
  	unsigned long max_freq = 0;
  
  	if (event != CPUFREQ_ADJUST || notify_device == NOTIFY_INVALID)
  		return 0;
  
  	if (cpumask_test_cpu(policy->cpu, &notify_device->allowed_cpus))
  		max_freq = notify_device->cpufreq_val;
  	else
  		return 0;
  
  	/* Never exceed user_policy.max */
  	if (max_freq > policy->user_policy.max)
  		max_freq = policy->user_policy.max;
  
  	if (policy->max != max_freq)
  		cpufreq_verify_within_limits(policy, 0, max_freq);
  
  	return 0;
  }
  
  /* cpufreq cooling device callback functions are defined below */
  
  /**
   * cpufreq_get_max_state - callback function to get the max cooling state.
   * @cdev: thermal cooling device pointer.
   * @state: fill this variable with the max cooling state.
   *
   * Callback for the thermal cooling device to return the cpufreq
   * max cooling state.
   *
   * Return: 0 on success, an error code otherwise.
   */
  static int cpufreq_get_max_state(struct thermal_cooling_device *cdev,
  				 unsigned long *state)
  {
  	struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;
  	struct cpumask *mask = &cpufreq_device->allowed_cpus;
  	unsigned int cpu;
  	unsigned int count = 0;
  	int ret;
  
  	cpu = cpumask_any(mask);
  
  	ret = get_property(cpu, 0, &count, GET_MAXL);
  
  	if (count > 0)
  		*state = count;
  
  	return ret;
  }
  
  /**
   * cpufreq_get_cur_state - callback function to get the current cooling state.
   * @cdev: thermal cooling device pointer.
   * @state: fill this variable with the current cooling state.
   *
   * Callback for the thermal cooling device to return the cpufreq
   * current cooling state.
   *
   * Return: 0 on success, an error code otherwise.
   */
  static int cpufreq_get_cur_state(struct thermal_cooling_device *cdev,
  				 unsigned long *state)
  {
  	struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;
  
  	*state = cpufreq_device->cpufreq_state;
  
  	return 0;
  }
  
  /**
   * cpufreq_set_cur_state - callback function to set the current cooling state.
   * @cdev: thermal cooling device pointer.
   * @state: set this variable to the current cooling state.
   *
   * Callback for the thermal cooling device to change the cpufreq
   * current cooling state.
   *
   * Return: 0 on success, an error code otherwise.
   */
  static int cpufreq_set_cur_state(struct thermal_cooling_device *cdev,
  				 unsigned long state)
  {
  	struct cpufreq_cooling_device *cpufreq_device = cdev->devdata;
  
  	return cpufreq_apply_cooling(cpufreq_device, state);
  }
  
  /* Bind cpufreq callbacks to thermal cooling device ops */
  static struct thermal_cooling_device_ops const cpufreq_cooling_ops = {
  	.get_max_state = cpufreq_get_max_state,
  	.get_cur_state = cpufreq_get_cur_state,
  	.set_cur_state = cpufreq_set_cur_state,
  };
  
  /* Notifier for cpufreq policy change */
  static struct notifier_block thermal_cpufreq_notifier_block = {
  	.notifier_call = cpufreq_thermal_notifier,
  };
  
  /**
   * __cpufreq_cooling_register - helper function to create cpufreq cooling device
   * @np: a valid struct device_node to the cooling device device tree node
   * @clip_cpus: cpumask of cpus where the frequency constraints will happen.
   *
   * This interface function registers the cpufreq cooling device with the name
   * "thermal-cpufreq-%x". This api can support multiple instances of cpufreq
   * cooling devices. It also gives the opportunity to link the cooling device
   * with a device tree node, in order to bind it via the thermal DT code.
   *
   * Return: a valid struct thermal_cooling_device pointer on success,
   * on failure, it returns a corresponding ERR_PTR().
   */
  static struct thermal_cooling_device *
  __cpufreq_cooling_register(struct device_node *np,
  			   const struct cpumask *clip_cpus)
  {
  	struct thermal_cooling_device *cool_dev;
  	struct cpufreq_cooling_device *cpufreq_dev = NULL;
  	unsigned int min = 0, max = 0;
  	char dev_name[THERMAL_NAME_LENGTH];
  	int ret = 0, i;
  	struct cpufreq_policy policy;
  
  	/* Verify that all the clip cpus have same freq_min, freq_max limit */
  	for_each_cpu(i, clip_cpus) {
  		/* continue if cpufreq policy not found and not return error */
  		if (!cpufreq_get_policy(&policy, i))
  			continue;
  		if (min == 0 && max == 0) {
  			min = policy.cpuinfo.min_freq;
  			max = policy.cpuinfo.max_freq;
  		} else {
  			if (min != policy.cpuinfo.min_freq ||
  			    max != policy.cpuinfo.max_freq)
  				return ERR_PTR(-EINVAL);
  		}
  	}
  	cpufreq_dev = kzalloc(sizeof(struct cpufreq_cooling_device),
  			      GFP_KERNEL);
  	if (!cpufreq_dev)
  		return ERR_PTR(-ENOMEM);
  
  	cpumask_copy(&cpufreq_dev->allowed_cpus, clip_cpus);
  
  	ret = get_idr(&cpufreq_idr, &cpufreq_dev->id);
  	if (ret) {
  		kfree(cpufreq_dev);
  		return ERR_PTR(-EINVAL);
  	}
  
  	snprintf(dev_name, sizeof(dev_name), "thermal-cpufreq-%d",
  		 cpufreq_dev->id);
  
  	cool_dev = thermal_of_cooling_device_register(np, dev_name, cpufreq_dev,
  						      &cpufreq_cooling_ops);
  	if (IS_ERR(cool_dev)) {
  		release_idr(&cpufreq_idr, cpufreq_dev->id);
  		kfree(cpufreq_dev);
  		return cool_dev;
  	}
  	cpufreq_dev->cool_dev = cool_dev;
  	cpufreq_dev->cpufreq_state = 0;
  	mutex_lock(&cooling_cpufreq_lock);
  
  	/* Register the notifier for first cpufreq cooling device */
  	if (cpufreq_dev_count == 0)
  		cpufreq_register_notifier(&thermal_cpufreq_notifier_block,
  					  CPUFREQ_POLICY_NOTIFIER);
  	cpufreq_dev_count++;
  
  	mutex_unlock(&cooling_cpufreq_lock);
  
  	return cool_dev;
  }
  
  /**
   * cpufreq_cooling_register - function to create cpufreq cooling device.
   * @clip_cpus: cpumask of cpus where the frequency constraints will happen.
   *
   * This interface function registers the cpufreq cooling device with the name
   * "thermal-cpufreq-%x". This api can support multiple instances of cpufreq
   * cooling devices.
   *
   * Return: a valid struct thermal_cooling_device pointer on success,
   * on failure, it returns a corresponding ERR_PTR().
   */
  struct thermal_cooling_device *
  cpufreq_cooling_register(const struct cpumask *clip_cpus)
  {
  	return __cpufreq_cooling_register(NULL, clip_cpus);
  }
  EXPORT_SYMBOL_GPL(cpufreq_cooling_register);
  
  /**
   * of_cpufreq_cooling_register - function to create cpufreq cooling device.
   * @np: a valid struct device_node to the cooling device device tree node
   * @clip_cpus: cpumask of cpus where the frequency constraints will happen.
   *
   * This interface function registers the cpufreq cooling device with the name
   * "thermal-cpufreq-%x". This api can support multiple instances of cpufreq
   * cooling devices. Using this API, the cpufreq cooling device will be
   * linked to the device tree node provided.
   *
   * Return: a valid struct thermal_cooling_device pointer on success,
   * on failure, it returns a corresponding ERR_PTR().
   */
  struct thermal_cooling_device *
  of_cpufreq_cooling_register(struct device_node *np,
  			    const struct cpumask *clip_cpus)
  {
  	if (!np)
  		return ERR_PTR(-EINVAL);
  
  	return __cpufreq_cooling_register(np, clip_cpus);
  }
  EXPORT_SYMBOL_GPL(of_cpufreq_cooling_register);
  
  /**
   * cpufreq_cooling_unregister - function to remove cpufreq cooling device.
   * @cdev: thermal cooling device pointer.
   *
   * This interface function unregisters the "thermal-cpufreq-%x" cooling device.
   */
  void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
  {
  	struct cpufreq_cooling_device *cpufreq_dev;
  
  	if (!cdev)
  		return;
  
  	cpufreq_dev = cdev->devdata;
  	mutex_lock(&cooling_cpufreq_lock);
  	cpufreq_dev_count--;
  
  	/* Unregister the notifier for the last cpufreq cooling device */
  	if (cpufreq_dev_count == 0)
  		cpufreq_unregister_notifier(&thermal_cpufreq_notifier_block,
  					    CPUFREQ_POLICY_NOTIFIER);
  	mutex_unlock(&cooling_cpufreq_lock);
  
  	thermal_cooling_device_unregister(cpufreq_dev->cool_dev);
  	release_idr(&cpufreq_idr, cpufreq_dev->id);
  	kfree(cpufreq_dev);
  }
  EXPORT_SYMBOL_GPL(cpufreq_cooling_unregister);