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    SubjectRe: [RFC PATCH 2/2] thermal: Add generic cpu cooling implementation
    From
    Hey Amit, I was able to use your code on an i.MX6Q thermal
    implementation and it seemed to work pretty well. Thanks for adding
    this. A couple of comments below.

    On Tue, Dec 13, 2011 at 9:13 AM, Amit Daniel Kachhap
    <amit.kachhap@linaro.org> wrote:
    > This patch adds support for generic cpu thermal cooling low level
    > implementations using frequency scaling and cpuhotplugg currently.
    > 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 API's return the
    > cooling device pointer.
    >
    > Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org>
    > ---
    >  Documentation/thermal/cpu-cooling-api.txt |   52 +++++
    >  drivers/thermal/Kconfig                   |   11 +
    >  drivers/thermal/Makefile                  |    1 +
    >  drivers/thermal/cpu_cooling.c             |  302 +++++++++++++++++++++++++++++
    >  include/linux/cpu_cooling.h               |   45 +++++
    >  5 files changed, 411 insertions(+), 0 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..d30b4f2
    > --- /dev/null
    > +++ b/Documentation/thermal/cpu-cooling-api.txt
    > @@ -0,0 +1,52 @@
    > +CPU cooling api's How To
    > +===================================
    > +
    > +Written by Amit Daniel Kachhap <amit.kachhap@linaro.org>
    > +
    > +Updated: 13 Dec 2011
    > +
    > +Copyright (c)  2011 Samsung Electronics Co., Ltd(http://www.samsung.com)
    > +
    > +0. Introduction
    > +
    > +The generic cpu cooling(freq clipping, cpuhotplug) provides
    > +registration/unregistration api's to the user. The binding of the cooling
    > +devices to the trip types is left for the user. The registration api's returns
    > +the cooling device pointer.
    > +
    > +1. cpufreq cooling api's
    > +
    > +1.1 cpufreq registration api's
    > +1.1.1 struct thermal_cooling_device *cpufreq_cooling_register(
    > +       struct freq_pctg_table *tab_ptr, unsigned int tab_size,
    > +       const struct cpumask *mask_val)
    > +
    > +    This interface function registers the cpufreq cooling device with the name
    > +       "thermal-cpufreq".
    > +
    > +    tab_ptr: The table containing the percentage of frequency to be clipped for
    > +    each cooling state.
    > +       .freq_clip_pctg[NR_CPUS]:Percentage of frequency to be clipped for each
    > +        cpu.
    > +       .polling_interval: polling interval for this cooling state.
    > +    tab_size: the total number of cooling state.
    > +    mask_val: all the allowed cpu's where frequency clipping can happen.
    > +
    > +1.1.2 void cpufreq_cooling_unregister(void)
    > +
    > +    This interface function unregisters the "thermal-cpufreq" cooling device.
    > +
    > +
    > +1.2 cpuhotplug registration api's
    > +
    > +1.2.1 struct thermal_cooling_device *cpuhotplug_cooling_register(
    > +       const struct cpumask *mask_val)
    > +
    > +    This interface function registers the cpuhotplug cooling device with the name
    > +       "thermal-cpuhotplug".
    > +
    > +    mask_val: all the allowed cpu's which can be hotplugged out.
    > +
    > +1.1.2 void cpuhotplug_cooling_unregister(void)
    > +
    > +    This interface function unregisters the "thermal-cpuhotplug" cooling device.
    > diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
    > index f7f71b2..298c1cd 100644
    > --- a/drivers/thermal/Kconfig
    > +++ b/drivers/thermal/Kconfig
    > @@ -18,3 +18,14 @@ config THERMAL_HWMON
    >        depends on THERMAL
    >        depends on HWMON=y || HWMON=THERMAL
    >        default y
    > +
    > +config CPU_THERMAL
    > +       bool "generic cpu cooling support"
    > +       depends on THERMAL
    > +       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.
    > diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
    > index 31108a0..655cbc4 100644
    > --- a/drivers/thermal/Makefile
    > +++ b/drivers/thermal/Makefile
    > @@ -3,3 +3,4 @@
    >  #
    >
    >  obj-$(CONFIG_THERMAL)          += thermal_sys.o
    > +obj-$(CONFIG_CPU_THERMAL)      += cpu_cooling.o
    > diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
    > new file mode 100644
    > index 0000000..cdd148c
    > --- /dev/null
    > +++ b/drivers/thermal/cpu_cooling.c
    > @@ -0,0 +1,302 @@
    > +/*
    > + *  linux/drivers/thermal/cpu_cooling.c
    > + *
    > + *  Copyright (C) 2011 Samsung Electronics Co., Ltd(http://www.samsung.com)
    > + *  Copyright (C) 2011  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/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>
    > +
    > +#ifdef CONFIG_CPU_FREQ
    > +struct cpufreq_cooling_device {
    > +       struct thermal_cooling_device *cool_dev;
    > +       struct freq_pctg_table *tab_ptr;
    > +       unsigned int tab_size;
    > +       unsigned int cpufreq_state;
    > +       const struct cpumask *allowed_cpus;
    > +};
    > +
    > +static struct cpufreq_cooling_device *cpufreq_device;
    > +
    > +/*Below codes defines functions to be used for cpufreq as cooling device*/
    > +static bool is_cpufreq_valid(int cpu)
    > +{
    > +       struct cpufreq_policy policy;
    > +       if (!cpufreq_get_policy(&policy, cpu))
    > +               return true;
    > +       return false;
    > +}
    > +
    > +static int cpufreq_apply_cooling(int cooling_state)
    > +{
    > +       int cpuid, this_cpu = smp_processor_id();
    > +
    > +       if (!is_cpufreq_valid(this_cpu))
    > +               return 0;
    > +
    > +       if (cooling_state > cpufreq_device->tab_size)
    > +               return -EINVAL;
    > +
    > +       /*Check if last cooling level is same as current cooling level*/
    > +       if (cpufreq_device->cpufreq_state == cooling_state)
    > +               return 0;
    > +
    > +       cpufreq_device->cpufreq_state = cooling_state;
    > +
    > +       for_each_cpu(cpuid, cpufreq_device->allowed_cpus) {
    > +               if (is_cpufreq_valid(cpuid))
    > +                       cpufreq_update_policy(cpuid);
    > +       }
    > +
    > +       return 0;
    > +}
    > +
    > +static int thermal_cpufreq_notifier(struct notifier_block *nb,
    > +                                       unsigned long event, void *data)
    > +{
    > +       struct cpufreq_policy *policy = data;
    > +       struct freq_pctg_table *th_table;
    > +       unsigned long max_freq = 0;
    > +       unsigned int cpu = policy->cpu, th_pctg = 0, level;
    > +
    > +       if (event != CPUFREQ_ADJUST)
    > +               return 0;
    > +
    > +       level = cpufreq_device->cpufreq_state;
    > +
    > +       if (level > 0) {
    > +               th_table =
    > +                       &(cpufreq_device->tab_ptr[level - 1]);
    > +               th_pctg = th_table->freq_clip_pctg[cpu];
    > +       }
    > +
    > +       max_freq =
    > +               (policy->cpuinfo.max_freq * (100 - th_pctg)) / 100;
    > +
    > +       cpufreq_verify_within_limits(policy, 0, max_freq);
    > +
    > +       return 0;
    > +}
    > +
    > +/*
    > + * cpufreq cooling device callback functions
    > + */
    > +static int cpufreq_get_max_state(struct thermal_cooling_device *cdev,
    > +                                unsigned long *state)
    > +{
    > +       *state = cpufreq_device->tab_size;
    > +       return 0;
    > +}
    > +
    > +static int cpufreq_get_cur_state(struct thermal_cooling_device *cdev,
    > +                                unsigned long *state)
    > +{
    > +       *state = cpufreq_device->cpufreq_state;
    > +       return 0;
    > +}
    > +
    > +/*This cooling may be as PASSIVE/STATE_ACTIVE type*/
    > +static int cpufreq_set_cur_state(struct thermal_cooling_device *cdev,
    > +                                unsigned long state)
    > +{
    > +       cpufreq_apply_cooling(state);
    > +       return 0;
    > +}
    > +
    > +/* bind cpufreq callbacks to cpufreq cooling device */
    > +static struct thermal_cooling_device_ops cpufreq_cooling_ops = {
    > +       .get_max_state = cpufreq_get_max_state,
    > +       .get_cur_state = cpufreq_get_cur_state,
    > +       .set_cur_state = cpufreq_set_cur_state,
    > +};
    > +
    > +static struct notifier_block thermal_cpufreq_notifier_block = {
    > +       .notifier_call = thermal_cpufreq_notifier,
    > +};
    > +
    > +struct thermal_cooling_device *cpufreq_cooling_register(
    > +       struct freq_pctg_table *tab_ptr, unsigned int tab_size,
    > +       const struct cpumask *mask_val)
    > +{
    > +       struct thermal_cooling_device *cool_dev;
    > +
    > +       if (tab_ptr == NULL || tab_size == 0)
    > +               return ERR_PTR(-EINVAL);
    > +
    > +       cpufreq_device =
    > +               kzalloc(sizeof(struct cpufreq_cooling_device), GFP_KERNEL);
    > +
    > +       if (!cpufreq_device)
    > +               return ERR_PTR(-ENOMEM);
    > +
    > +       cool_dev = thermal_cooling_device_register("thermal-cpufreq", NULL,
    > +                                               &cpufreq_cooling_ops);
    > +       if (!cool_dev) {
    > +               kfree(cpufreq_device);
    > +               return ERR_PTR(-EINVAL);
    > +       }
    > +
    > +       cpufreq_device->tab_ptr = tab_ptr;
    > +       cpufreq_device->tab_size = tab_size;
    > +       cpufreq_device->cool_dev = cool_dev;
    > +       cpufreq_device->allowed_cpus = mask_val;
    > +
    > +       cpufreq_register_notifier(&thermal_cpufreq_notifier_block,
    > +                                               CPUFREQ_POLICY_NOTIFIER);
    > +       return cool_dev;
    > +}
    > +EXPORT_SYMBOL(cpufreq_cooling_register);
    > +
    > +void cpufreq_cooling_unregister(void)
    > +{
    > +       cpufreq_unregister_notifier(&thermal_cpufreq_notifier_block,
    > +                                               CPUFREQ_POLICY_NOTIFIER);
    > +       thermal_cooling_device_unregister(cpufreq_device->cool_dev);
    > +       kfree(cpufreq_device);
    > +}
    > +EXPORT_SYMBOL(cpufreq_cooling_unregister);
    > +#else /*!CONFIG_CPU_FREQ*/
    > +struct thermal_cooling_device *cpufreq_cooling_register(
    > +       struct freq_pctg_table *tab_ptr, unsigned int tab_size)

    Need to add the "const struct cpumask *mask_val" parameter
    to this function like it's used above and prototyped in the heard
    or else it causes a build error when building
    without CONFIG_CPU_FREQ defined.

    > +{
    > +       return NULL;
    > +}
    > +EXPORT_SYMBOL(cpufreq_cooling_register);
    > +void cpufreq_cooling_unregister(void)
    > +{
    > +       return;
    > +}
    > +EXPORT_SYMBOL(cpufreq_cooling_unregister);
    > +#endif /*CONFIG_CPU_FREQ*/
    > +
    > +#ifdef CONFIG_HOTPLUG_CPU
    > +
    > +struct hotplug_cooling_device {
    > +       struct thermal_cooling_device *cool_dev;
    > +       unsigned int hotplug_state;
    > +       const struct cpumask *allowed_cpus;
    > +};
    > +static struct hotplug_cooling_device *hotplug_device;
    > +
    > +/*
    > + * cpu hotplug cooling device callback functions
    > + */
    > +static int cpuhotplug_get_max_state(struct thermal_cooling_device *cdev,
    > +                                unsigned long *state)
    > +{
    > +       *state = 1;
    > +       return 0;
    > +}
    > +
    > +static int cpuhotplug_get_cur_state(struct thermal_cooling_device *cdev,
    > +                                unsigned long *state)
    > +{
    > +       /*This cooling device may be of type ACTIVE, so state field
    > +       can be 0 or 1*/
    > +       *state = hotplug_device->hotplug_state;
    > +       return 0;
    > +}
    > +
    > +/*This cooling may be as PASSIVE/STATE_ACTIVE type*/
    > +static int cpuhotplug_set_cur_state(struct thermal_cooling_device *cdev,
    > +                                unsigned long state)
    > +{
    > +       int cpuid, this_cpu = smp_processor_id();
    > +
    > +       if (hotplug_device->hotplug_state == state)
    > +               return 0;
    > +
    > +       /*This cooling device may be of type ACTIVE, so state field
    > +       can be 0 or 1*/
    > +       if (state == 1) {
    > +               for_each_cpu(cpuid, hotplug_device->allowed_cpus) {
    > +                       if (cpu_online(cpuid) && (cpuid != this_cpu))
    > +                               cpu_down(cpuid);
    > +               }
    > +       } else if (state == 0) {
    > +               for_each_cpu(cpuid, hotplug_device->allowed_cpus) {
    > +                       if (!cpu_online(cpuid) && (cpuid != this_cpu))
    > +                               cpu_up(cpuid);
    > +               }
    > +       } else
    > +               return -EINVAL;
    > +

    I don't like how ACTIVE does not have available notification callbacks
    like HOT and CRITICAL do. Perhaps I fail to grasp why they aren't there
    but besides just applying a cooling device, one might want to do something
    else as well upon hitting these trip points. So that said, it might be nice
    to add a notification to STATE_ACTIVE as well.

    > +       hotplug_device->hotplug_state = state;
    > +
    > +       return 0;
    > +}
    > +/* bind hotplug callbacks to cpu hotplug cooling device */
    > +static struct thermal_cooling_device_ops cpuhotplug_cooling_ops = {
    > +       .get_max_state = cpuhotplug_get_max_state,
    > +       .get_cur_state = cpuhotplug_get_cur_state,
    > +       .set_cur_state = cpuhotplug_set_cur_state,
    > +};
    > +
    > +struct thermal_cooling_device *cpuhotplug_cooling_register(
    > +       const struct cpumask *mask_val)
    > +{
    > +       struct thermal_cooling_device *cool_dev;
    > +
    > +       hotplug_device =
    > +               kzalloc(sizeof(struct hotplug_cooling_device), GFP_KERNEL);
    > +
    > +       if (!hotplug_device)
    > +               return ERR_PTR(-ENOMEM);
    > +
    > +       cool_dev = thermal_cooling_device_register("thermal-cpuhotplug", NULL,
    > +                                               &cpuhotplug_cooling_ops);
    > +       if (!cool_dev) {
    > +               kfree(hotplug_device);
    > +               return ERR_PTR(-EINVAL);
    > +       }
    > +
    > +       hotplug_device->cool_dev = cool_dev;
    > +       hotplug_device->hotplug_state = 0;
    > +       hotplug_device->allowed_cpus = mask_val;
    > +
    > +       return cool_dev;
    > +}
    > +EXPORT_SYMBOL(cpuhotplug_cooling_register);
    > +
    > +void cpuhotplug_cooling_unregister(void)
    > +{
    > +       thermal_cooling_device_unregister(hotplug_device->cool_dev);
    > +       kfree(hotplug_device);
    > +}
    > +EXPORT_SYMBOL(cpuhotplug_cooling_unregister);
    > +#else /*!CONFIG_HOTPLUG_CPU*/
    > +struct thermal_cooling_device *cpuhotplug_cooling_register(
    > +       const struct cpumask *mask_val)
    > +{
    > +       return NULL;
    > +}
    > +EXPORT_SYMBOL(cpuhotplug_cooling_register);
    > +void cpuhotplug_cooling_unregister(void)
    > +{
    > +       return;
    > +}
    > +EXPORT_SYMBOL(cpuhotplug_cooling_unregister);
    > +#endif /*CONFIG_HOTPLUG_CPU*/
    > diff --git a/include/linux/cpu_cooling.h b/include/linux/cpu_cooling.h
    > new file mode 100644
    > index 0000000..0c57375
    > --- /dev/null
    > +++ b/include/linux/cpu_cooling.h
    > @@ -0,0 +1,45 @@
    > +/*
    > + *  linux/include/linux/cpu_cooling.h
    > + *
    > + *  Copyright (C) 2011 Samsung Electronics Co., Ltd(http://www.samsung.com)
    > + *  Copyright (C) 2011  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.
    > + *
    > + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    > + */
    > +
    > +#ifndef __CPU_COOLING_H__
    > +#define __CPU_COOLING_H__
    > +
    > +#include <linux/thermal.h>
    > +
    > +struct freq_pctg_table {
    > +       unsigned int freq_clip_pctg[NR_CPUS];
    > +       unsigned int polling_interval;
    > +};
    > +
    > +extern struct thermal_cooling_device *cpufreq_cooling_register(
    > +       struct freq_pctg_table *tab_ptr, unsigned int tab_size,
    > +       const struct cpumask *mask_val);
    > +
    > +extern void cpufreq_cooling_unregister(void);
    > +
    > +extern struct thermal_cooling_device *cpuhotplug_cooling_register(
    > +       const struct cpumask *mask_val);
    > +
    > +extern void cpuhotplug_cooling_unregister(void);
    > +
    > +#endif /* __CPU_COOLING_H__ */
    > --
    > 1.7.1
    >
    > --
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