Linux Power Management development

* Re: [PATCH v4 1/5] thermal: Add generic cpufreq cooling implementation
From: Rob Lee @ 2012-06-26  3:12 UTC (permalink / raw)
  To: Amit Daniel Kachhap
  Cc: linux-samsung-soc-u79uwXL29TY76Z2rM5mHXA,
	durgadoss.r-ral2JQCrhuEAvxtiuMwx3w,
	patches-QSEj5FYQhm4dnm+yROfE0A,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA,
	lm-sensors-GZX6beZjE8VD60Wz+7aTrA,
	linux-acpi-u79uwXL29TY76Z2rM5mHXA,
	rui.zhang-ral2JQCrhuEAvxtiuMwx3w, khali-PUYAD+kWke1g9hUCZPvPmw,
	linaro-dev-cunTk1MwBs8s++Sfvej+rw,
	linux-pm-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA,
	lenb-DgEjT+Ai2ygdnm+yROfE0A,
	akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b,
	guenter.roeck-IzeFyvvaP7pWk0Htik3J/w
In-Reply-To: <1336815645-29625-2-git-send-email-amit.kachhap-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>

Hey Amit,

I was just re-organizing the imx thermal driver that uses this cpu
cooling interface and noticed a couple of small issues here.   If
these suggestions are agreed upon and if it's too late for these
issues be changed with this patchset, I can submit them separately
unless you'd prefer to.

On Sat, May 12, 2012 at 4:40 AM, Amit Daniel Kachhap
<amit.kachhap-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:
> 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.
>
> Signed-off-by: Amit Daniel Kachhap <amit.kachhap-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> ---
>  Documentation/thermal/cpu-cooling-api.txt |   60 ++++
>  drivers/thermal/Kconfig                   |   11 +
>  drivers/thermal/Makefile                  |    3 +-
>  drivers/thermal/cpu_cooling.c             |  483 +++++++++++++++++++++++++++++
>  include/linux/cpu_cooling.h               |   99 ++++++
>  5 files changed, 655 insertions(+), 1 deletions(-)
>  create mode 100644 Documentation/thermal/cpu-cooling-api.txt
>  create mode 100644 drivers/thermal/cpu_cooling.c
>  create mode 100644 include/linux/cpu_cooling.h
>
> diff --git a/Documentation/thermal/cpu-cooling-api.txt b/Documentation/thermal/cpu-cooling-api.txt
> new file mode 100644
> index 0000000..557adb8
> --- /dev/null
> +++ b/Documentation/thermal/cpu-cooling-api.txt
> @@ -0,0 +1,60 @@
> +CPU cooling APIs How To
> +===================================
> +
> +Written by Amit Daniel Kachhap <amit.kachhap-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> +
> +Updated: 12 May 2012
> +
> +Copyright (c)  2012 Samsung Electronics Co., Ltd(http://www.samsung.com)
> +
> +0. Introduction
> +
> +The generic cpu cooling(freq clipping, cpuhotplug etc) 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)
> +
> +    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.
> +       .temp_level: Temperature level at which the frequency clamping will
> +       happen.
> +       .mask_val: cpumask of the allowed cpu's
> +    tab_size: the total number of cpufreq cooling states.
> +
> +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.
> +
> +
> +1.2 CPU cooling action notifier register/unregister interface
> +1.2.1 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_START or CPUFREQ_COOLING_STOP
> +
> +1.2.2 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_START or CPUFREQ_COOLING_STOP
> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> index 514a691..d9c529f 100644
> --- a/drivers/thermal/Kconfig
> +++ b/drivers/thermal/Kconfig
> @@ -19,6 +19,17 @@ config THERMAL_HWMON
>        depends on HWMON=y || HWMON=THERMAL
>        default y
>
> +config CPU_THERMAL

Perhaps the name CPU_COOLING or CPUFREQ_COOLING would more accurately
describe this functionality?  I like the latter since now this
mechanism only supports cooling by using cpufreq.

> +       bool "generic cpu cooling support"

If we use CPUFREQ_COOLING, then perhaps this could say:

bool "cpu cooling through cpufreq frequency limiting"

> +       depends on THERMAL && CPU_FREQ
> +       help
> +         This implements the generic cpu cooling mechanism through frequency
> +         reduction, cpu hotplug and any other ways of reducing temperature. An
> +         ACPI version of this already exists(drivers/acpi/processor_thermal.c).
> +         This will be useful for platforms using the generic thermal interface
> +         and not the ACPI interface.
> +         If you want this support, you should say Y or M here.
> +

Currently, only the "frequency reduction" method exists so perhaps
it's best to remove mention of "cpu hotplug and any other ways of
reducing temperature"?  Here'as a version for cpufreq only:

config CPUFREQ_COOLING
	bool "cpu cooling through cpufreq frequency limiting"
	depends on THERMAL && CPU_FREQ
	help
	  This implements a generic cpu cooling mechanism through cpufreq
	  frequency limiting. An ACPI version of this already exists
	  (drivers/acpi/processor_thermal.c).  This will be useful for
	  platforms using the generic thermal interface and not the ACPI
	  interface.
	  If you want this support, you should say Y or M here.

>  config SPEAR_THERMAL
>        bool "SPEAr thermal sensor driver"
>        depends on THERMAL
> diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
> index a9fff0b..30c456c 100644
> --- a/drivers/thermal/Makefile
> +++ b/drivers/thermal/Makefile
> @@ -3,4 +3,5 @@
>  #
>
>  obj-$(CONFIG_THERMAL)          += thermal_sys.o
> -obj-$(CONFIG_SPEAR_THERMAL)            += spear_thermal.o
> \ No newline at end of file
> +obj-$(CONFIG_CPU_THERMAL)       += cpu_cooling.o
> +obj-$(CONFIG_SPEAR_THERMAL)            += spear_thermal.o
> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
> new file mode 100644
> index 0000000..c40d9a0
> --- /dev/null
> +++ b/drivers/thermal/cpu_cooling.c
> @@ -0,0 +1,483 @@
> +/*
> + *  linux/drivers/thermal/cpu_cooling.c
> + *
> + *  Copyright (C) 2012 Samsung Electronics Co., Ltd(http://www.samsung.com)
> + *  Copyright (C) 2012  Amit Daniel <amit.kachhap-QSEj5FYQhm4dnm+yROfE0A@public.gmane.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/kernel.h>
> +#include <linux/module.h>
> +#include <linux/thermal.h>
> +#include <linux/platform_device.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
> + * @id: unique integer value corresponding to each cpufreq_cooling_device
> + *     registered.
> + * @cool_dev: thermal_cooling_device pointer to keep track of the the
> + *     egistered cooling device.
> + * @tab_ptr: freq_clip_table table containing the maximum value of frequency to
> + *     be set for different cooling state.
> + * @tab_size: integer value representing a count of the above table.
> + * @cpufreq_state: integer value representing the current state of cpufreq
> + *     cooling devices.
> + * @allowed_cpus: all the cpus involved for this cpufreq_cooling_device.
> + * @node: list_head to link all cpufreq_cooling_device together.
> + *
> + * This structure is required for keeping information of each
> + * cpufreq_cooling_device registered as a list whose head is represented by
> + * cooling_cpufreq_list. In order to prevent corruption of this list a
> + * mutex lock cooling_cpufreq_lock is used.
> + */
> +struct cpufreq_cooling_device {
> +       int id;
> +       struct thermal_cooling_device *cool_dev;
> +       struct freq_clip_table *tab_ptr;
> +       unsigned int tab_size;
> +       unsigned int cpufreq_state;
> +       struct cpumask allowed_cpus;
> +       struct list_head node;
> +};
> +static LIST_HEAD(cooling_cpufreq_list);
> +static DEFINE_MUTEX(cooling_cpufreq_lock);
> +static DEFINE_IDR(cpufreq_idr);
> +
> +/*per cpu variable to store the previous max frequency allowed*/
> +static DEFINE_PER_CPU(unsigned int, max_policy_freq);
> +
> +/*notify_table passes value to the CPUFREQ_ADJUST callback function.*/
> +#define NOTIFY_INVALID NULL
> +static struct freq_clip_table *notify_table;
> +
> +/*Head of the blocking notifier chain to inform about frequency clamping*/
> +static BLOCKING_NOTIFIER_HEAD(cputherm_state_notifier_list);
> +
> +/**
> + * get_idr - function to get a unique id.
> + * @idr: struct idr * handle used to create a id.
> + * @id: int * value generated by this function.
> + */
> +static int get_idr(struct idr *idr, int *id)
> +{
> +       int err;
> +again:
> +       if (unlikely(idr_pre_get(idr, GFP_KERNEL) == 0))
> +               return -ENOMEM;
> +
> +       mutex_lock(&cooling_cpufreq_lock);
> +       err = idr_get_new(idr, NULL, id);
> +       mutex_unlock(&cooling_cpufreq_lock);
> +
> +       if (unlikely(err == -EAGAIN))
> +               goto again;
> +       else if (unlikely(err))
> +               return err;
> +
> +       *id = *id & MAX_ID_MASK;
> +       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);
> +}
> +
> +/**
> + * cputherm_register_notifier - Register a notifier with cpu cooling interface.
> + * @nb:        struct notifier_block * with callback info.
> + * @list: integer value for which notification is needed. possible values are
> + *     CPUFREQ_COOLING_START and CPUFREQ_COOLING_STOP.
> + *
> + * This exported function registers a driver with cpu cooling layer. The driver
> + * will be notified when any cpu cooling action is called.
> + */
> +int cputherm_register_notifier(struct notifier_block *nb, unsigned int list)
> +{
> +       int ret = 0;
> +
> +       switch (list) {
> +       case CPUFREQ_COOLING_START:
> +       case CPUFREQ_COOLING_STOP:
> +               ret = blocking_notifier_chain_register(
> +                               &cputherm_state_notifier_list, nb);
> +               break;
> +       default:
> +               ret = -EINVAL;
> +       }
> +       return ret;
> +}
> +EXPORT_SYMBOL(cputherm_register_notifier);
> +
> +/**
> + * cputherm_unregister_notifier - Un-register a notifier.
> + * @nb:        struct notifier_block * with callback info.
> + * @list: integer value for which notification is needed. values possible are
> + *     CPUFREQ_COOLING_START or CPUFREQ_COOLING_STOP.
> + *
> + * This exported function un-registers a driver with cpu cooling layer.
> + */
> +int cputherm_unregister_notifier(struct notifier_block *nb, unsigned int list)
> +{
> +       int ret = 0;
> +
> +       switch (list) {
> +       case CPUFREQ_COOLING_START:
> +       case CPUFREQ_COOLING_STOP:
> +               ret = blocking_notifier_chain_unregister(
> +                               &cputherm_state_notifier_list, nb);
> +               break;
> +       default:
> +               ret = -EINVAL;
> +       }
> +       return ret;
> +}
> +EXPORT_SYMBOL(cputherm_unregister_notifier);
> +
> +/*Below codes defines functions to be used for cpufreq as cooling device*/
> +
> +/**
> + * is_cpufreq_valid - function to check if a cpu has frequency transition policy.
> + * @cpu: cpu for which check is needed.
> + */
> +static int is_cpufreq_valid(int cpu)
> +{
> +       struct cpufreq_policy policy;
> +       return !cpufreq_get_policy(&policy, cpu);
> +}
> +
> +/**
> + * 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.
> + */
> +static int cpufreq_apply_cooling(struct cpufreq_cooling_device *cpufreq_device,
> +                               unsigned long cooling_state)
> +{
> +       unsigned int event, cpuid, state;
> +       struct freq_clip_table *th_table, *table_ptr;
> +       const struct cpumask *maskPtr = &cpufreq_device->allowed_cpus;
> +       struct cpufreq_cooling_device *cpufreq_ptr;
> +
> +       if (cooling_state > cpufreq_device->tab_size)
> +               return -EINVAL;
> +
> +       /*Check if the old cooling action is same as new cooling action*/
> +       if (cpufreq_device->cpufreq_state == cooling_state)
> +               return 0;
> +
> +       /*pass cooling table info to the cpufreq_thermal_notifier callback*/
> +       notify_table = NOTIFY_INVALID;
> +
> +       if (cooling_state > 0) {
> +               th_table = &(cpufreq_device->tab_ptr[cooling_state - 1]);
> +               notify_table = th_table;
> +       }
> +
> +       /*check if any lower clip frequency active in other cpufreq_device's*/
> +       list_for_each_entry(cpufreq_ptr, &cooling_cpufreq_list, node) {
> +
> +               state = cpufreq_ptr->cpufreq_state;
> +               if (state == 0 || cpufreq_ptr == cpufreq_device)
> +                       continue;
> +
> +               if (!cpumask_equal(&cpufreq_ptr->allowed_cpus,
> +                               &cpufreq_device->allowed_cpus))
> +                       continue;
> +
> +               table_ptr = &(cpufreq_ptr->tab_ptr[state - 1]);
> +               if (notify_table == NULL ||
> +                               (table_ptr->freq_clip_max <
> +                               notify_table->freq_clip_max))
> +                       notify_table =  table_ptr;
> +       }
> +
> +       cpufreq_device->cpufreq_state = cooling_state;
> +
> +       if (notify_table != NOTIFY_INVALID) {
> +               event = CPUFREQ_COOLING_START;
> +               maskPtr = notify_table->mask_val;
> +       } else {
> +               event = CPUFREQ_COOLING_STOP;
> +       }
> +
> +       blocking_notifier_call_chain(&cputherm_state_notifier_list,
> +                                               event, notify_table);
> +
> +       for_each_cpu(cpuid, maskPtr) {
> +               if (is_cpufreq_valid(cpuid))
> +                       cpufreq_update_policy(cpuid);
> +       }
> +
> +       notify_table = 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
> + */
> +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)
> +               return 0;
> +
> +       if (notify_table != NOTIFY_INVALID) {
> +               max_freq = notify_table->freq_clip_max;
> +
> +               if (!per_cpu(max_policy_freq, policy->cpu))
> +                       per_cpu(max_policy_freq, policy->cpu) = policy->max;
> +       } else {
> +               if (per_cpu(max_policy_freq, policy->cpu)) {
> +                       max_freq = per_cpu(max_policy_freq, policy->cpu);
> +                       per_cpu(max_policy_freq, policy->cpu) = 0;
> +               } else {
> +                       max_freq = policy->max;
> +               }
> +       }
> +
> +       /* 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.
> + */
> +static int cpufreq_get_max_state(struct thermal_cooling_device *cdev,
> +                                unsigned long *state)
> +{
> +       int ret = -EINVAL;
> +       struct cpufreq_cooling_device *cpufreq_device;
> +
> +       mutex_lock(&cooling_cpufreq_lock);
> +       list_for_each_entry(cpufreq_device, &cooling_cpufreq_list, node) {
> +               if (cpufreq_device && cpufreq_device->cool_dev == cdev) {
> +                       *state = cpufreq_device->tab_size;
> +                       ret = 0;
> +                       break;
> +               }
> +       }
> +       mutex_unlock(&cooling_cpufreq_lock);
> +       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.
> + */
> +static int cpufreq_get_cur_state(struct thermal_cooling_device *cdev,
> +                                unsigned long *state)
> +{
> +       int ret = -EINVAL;
> +       struct cpufreq_cooling_device *cpufreq_device;
> +
> +       mutex_lock(&cooling_cpufreq_lock);
> +       list_for_each_entry(cpufreq_device, &cooling_cpufreq_list, node) {
> +               if (cpufreq_device && cpufreq_device->cool_dev == cdev) {
> +                       *state = cpufreq_device->cpufreq_state;
> +                       ret = 0;
> +                       break;
> +               }
> +       }
> +       mutex_unlock(&cooling_cpufreq_lock);
> +       return ret;
> +}
> +
> +/**
> + * 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.
> + */
> +static int cpufreq_set_cur_state(struct thermal_cooling_device *cdev,
> +                                unsigned long state)
> +{
> +       int ret = -EINVAL;
> +       struct cpufreq_cooling_device *cpufreq_device;
> +
> +       mutex_lock(&cooling_cpufreq_lock);
> +       list_for_each_entry(cpufreq_device, &cooling_cpufreq_list, node) {
> +               if (cpufreq_device && cpufreq_device->cool_dev == cdev) {
> +                       ret = 0;
> +                       break;
> +               }
> +       }
> +       if (!ret)
> +               ret = cpufreq_apply_cooling(cpufreq_device, state);
> +
> +       mutex_unlock(&cooling_cpufreq_lock);
> +
> +       return ret;
> +}
> +
> +/*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 - function to create cpufreq cooling device.
> + * @tab_ptr: table ptr containing the maximum value of frequency to be clipped
> + *     for each cooling state.
> + * @tab_size: count of entries in the above table.
> + *     happen.
> + */
> +struct thermal_cooling_device *cpufreq_cooling_register(
> +       struct freq_clip_table *tab_ptr, unsigned int tab_size)
> +{
> +       struct thermal_cooling_device *cool_dev;
> +       struct cpufreq_cooling_device *cpufreq_dev = NULL;
> +       struct freq_clip_table *clip_tab;
> +       unsigned int cpufreq_dev_count = 0;
> +       char dev_name[THERMAL_NAME_LENGTH];
> +       int ret = 0, id = 0, i;
> +
> +       if (tab_ptr == NULL || tab_size == 0)
> +               return ERR_PTR(-EINVAL);
> +
> +       list_for_each_entry(cpufreq_dev, &cooling_cpufreq_list, node)
> +               cpufreq_dev_count++;
> +
> +       cpufreq_dev = kzalloc(sizeof(struct cpufreq_cooling_device),
> +                       GFP_KERNEL);
> +       if (!cpufreq_dev)
> +               return ERR_PTR(-ENOMEM);
> +
> +       /*Verify that all the entries of freq_clip_table are present*/
> +       for (i = 0; i < tab_size; i++) {
> +               clip_tab = ((struct freq_clip_table *)&tab_ptr[i]);
> +               if (!clip_tab->freq_clip_max || !clip_tab->mask_val
> +                                       || !clip_tab->temp_level) {
> +                       kfree(cpufreq_dev);
> +                       return ERR_PTR(-EINVAL);
> +               }
> +               /*
> +                *Consolidate all the cpumask for all the individual entries
> +                *of the trip table. This is useful in resetting all the
> +                *clipped frequencies to the normal level for each cpufreq
> +                *cooling device.
> +                */
> +               cpumask_or(&cpufreq_dev->allowed_cpus,
> +                       &cpufreq_dev->allowed_cpus, clip_tab->mask_val);
> +       }
> +
> +       cpufreq_dev->tab_ptr = tab_ptr;
> +       cpufreq_dev->tab_size = tab_size;
> +
> +       ret = get_idr(&cpufreq_idr, &cpufreq_dev->id);
> +       if (ret) {
> +               kfree(cpufreq_dev);
> +               return ERR_PTR(-EINVAL);
> +       }
> +
> +       sprintf(dev_name, "thermal-cpufreq-%d", cpufreq_dev->id);
> +
> +       cool_dev = thermal_cooling_device_register(dev_name, cpufreq_dev,
> +                                               &cpufreq_cooling_ops);
> +       if (!cool_dev) {
> +               release_idr(&cpufreq_idr, cpufreq_dev->id);
> +               kfree(cpufreq_dev);
> +               return ERR_PTR(-EINVAL);
> +       }
> +       cpufreq_dev->id = id;
> +       cpufreq_dev->cool_dev = cool_dev;
> +       mutex_lock(&cooling_cpufreq_lock);
> +       list_add_tail(&cpufreq_dev->node, &cooling_cpufreq_list);
> +
> +       /*Register the notifier for first cpufreq cooling device*/
> +       if (cpufreq_dev_count == 0)
> +               cpufreq_register_notifier(&thermal_cpufreq_notifier_block,
> +                                               CPUFREQ_POLICY_NOTIFIER);
> +
> +       mutex_unlock(&cooling_cpufreq_lock);
> +       return cool_dev;
> +}
> +EXPORT_SYMBOL(cpufreq_cooling_register);
> +
> +/**
> + * cpufreq_cooling_unregister - function to remove cpufreq cooling device.
> + * @cdev: thermal cooling device pointer.
> + */
> +void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
> +{
> +       struct cpufreq_cooling_device *cpufreq_dev = NULL;
> +       unsigned int cpufreq_dev_count = 0;
> +
> +       mutex_lock(&cooling_cpufreq_lock);
> +       list_for_each_entry(cpufreq_dev, &cooling_cpufreq_list, node) {
> +               if (cpufreq_dev && cpufreq_dev->cool_dev == cdev)
> +                       break;
> +               cpufreq_dev_count++;
> +       }
> +
> +       if (!cpufreq_dev || cpufreq_dev->cool_dev != cdev) {
> +               mutex_unlock(&cooling_cpufreq_lock);
> +               return;
> +       }
> +
> +       list_del(&cpufreq_dev->node);
> +
> +       /*Unregister the notifier for the last cpufreq cooling device*/
> +       if (cpufreq_dev_count == 1) {
> +               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(cpufreq_cooling_unregister);
> diff --git a/include/linux/cpu_cooling.h b/include/linux/cpu_cooling.h
> new file mode 100644
> index 0000000..ed6c096
> --- /dev/null
> +++ b/include/linux/cpu_cooling.h
> @@ -0,0 +1,99 @@
> +/*
> + *  linux/include/linux/cpu_cooling.h
> + *
> + *  Copyright (C) 2012 Samsung Electronics Co., Ltd(http://www.samsung.com)
> + *  Copyright (C) 2012  Amit Daniel <amit.kachhap-QSEj5FYQhm4dnm+yROfE0A@public.gmane.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.
> + *
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + */
> +
> +#ifndef __CPU_COOLING_H__
> +#define __CPU_COOLING_H__
> +
> +#include <linux/thermal.h>
> +
> +#define CPUFREQ_COOLING_START          0
> +#define CPUFREQ_COOLING_STOP           1
> +
> +/**
> + * struct freq_clip_table
> + * @freq_clip_max: maximum frequency allowed for this cooling state.
> + * @temp_level: Temperature level at which the temperature clipping will
> + *     happen.
> + * @mask_val: cpumask of the allowed cpu's where the clipping will take place.
> + *
> + * This structure is required to be filled and passed to the
> + * cpufreq_cooling_unregister function.
> + */
> +struct freq_clip_table {
> +       unsigned int freq_clip_max;
> +       unsigned int temp_level;
> +       const struct cpumask *mask_val;
> +};
> +
> +/**
> + * cputherm_register_notifier - Register a notifier with cpu cooling interface.
> + * @nb:        struct notifier_block * with callback info.
> + * @list: integer value for which notification is needed. possible values are
> + *     CPUFREQ_COOLING_TYPE and CPUHOTPLUG_COOLING_TYPE.

CPUFREQ_COOLING_TYPE and CPUHOTPLUG_COOLING_TYPE should be changed to
CPUFREQ_COOLING_START CPUFREQ_COOLING_STOP, right?

> + *
> + * This exported function registers a driver with cpu cooling layer. The driver
> + * will be notified when any cpu cooling action is called.
> + */
> +int cputherm_register_notifier(struct notifier_block *nb, unsigned int list);
> +
> +/**
> + * cputherm_unregister_notifier - Un-register a notifier.
> + * @nb:        struct notifier_block * with callback info.
> + * @list: integer value for which notification is needed. values possible are
> + *     CPUFREQ_COOLING_TYPE.

Should be changed to CPUFREQ_COOLING_START, CPUFREQ_COOLING_STOP, right?

> + *
> + * This exported function un-registers a driver with cpu cooling layer.
> + */
> +int cputherm_unregister_notifier(struct notifier_block *nb, unsigned int list);
> +
> +#ifdef CONFIG_CPU_FREQ

Consider changing this to "#ifdef CPU_THERMAL"  A platform thermal
driver may want to always call this function as its cpu cooling
mechanism but it should still function without the cpu_cooling being
enabled.  In this case, the platform thermal driver would only provide
temperature readings and critical trip point handling.  But if the
platform happened may have CONFIG_CPU_FREQ enabled, a build error
would occur in the current implementation.

(the CONFIG_CPU_FREQ requirement will be met by CPU_THERMAL being
enabled since it also implies CONFIG_CPU_FREQ being enabled per the
Kconfig dependency)

> +/**
> + * cpufreq_cooling_register - function to create cpufreq cooling device.
> + * @tab_ptr: table ptr containing the maximum value of frequency to be clipped
> + *     for each cooling state.
> + * @tab_size: count of entries in the above table.
> + * @mask_val: cpumask containing the allowed cpu's where frequency clipping can
> + *     happen.
> + */
> +struct thermal_cooling_device *cpufreq_cooling_register(
> +       struct freq_clip_table *tab_ptr, unsigned int tab_size);
> +
> +/**
> + * cpufreq_cooling_unregister - function to remove cpufreq cooling device.
> + * @cdev: thermal cooling device pointer.
> + */
> +void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev);
> +#else /*!CONFIG_CPU_FREQ*/

Modify comment if above suggestion is taken.

> +static inline struct thermal_cooling_device *cpufreq_cooling_register(
> +       struct freq_clip_table *tab_ptr, unsigned int tab_size);
> +{
> +       return NULL;
> +}
> +static inline void cpufreq_cooling_unregister(
> +               struct thermal_cooling_device *cdev)
> +{
> +       return;
> +}
> +#endif /*CONFIG_CPU_FREQ*/

Modify comment if above suggestion is taken.

> +
> +#endif /* __CPU_COOLING_H__ */
> --
> 1.7.1
>
>
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