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    SubjectRe: [linux-pm] [RFC PATCH 2/2] thermal: Add generic cpu cooling implementation
    From
    Hi eduardo,

    Again thanks for the review.

    On 7 February 2012 00:25, Eduardo Valentin <eduardo.valentin@ti.com> wrote:
    > Hello Amit,
    >
    > On Tue, Dec 13, 2011 at 08:43:16PM +0530, Amit Daniel Kachhap 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)
    >> +{
    >
    > Why do you need cooling_state to be signed? You used it always against
    > unsigned values. Besides, the thermal api imposes unsigned long.
    Yes, unsigned long is a better way.
    >
    >> +     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;
    >
    >
    > Might be interesting to extend this a bit. You could have the
    > above as default policy setup, but you could also allow people
    > to change this behavior. For instance, adding some callback option
    > while registering the cooling device (or a notifier), which would
    > determine the max_freq for the generic layer. The mechanism to
    > deploy max_freq into the system must be generic enough with cpufreq
    > APIs, but the decision to which max_freq to use, could be specific.
    > Don't you think?
    I agree that there will always some constraints on the system to cap
    the max frequency. But these thermal clippings is called for rare
    scenarios. Anyway, Your idea is worth considering. I will check if
    cpufreq has any generic way of achieving this.
    >
    >> +
    >> +     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)
    >> +{
    >> +     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*/
    >
    > /*
    >  * Small thing. Check the style for multi line comments.
    >  * This is also an example.
    >  */
    Ok.
    >
    >> +     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;
    >> +
    >> +     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);
    >
    > I suppose your original idea was to have this function called only once right?
    > I'd suggest to add some documentation on this header file to specify this.
    >
    > Besides, the fact that you receive a cpumask may suggest you could register
    > different cooling device for subsets of your system cpus.
    >
    > In any case, if you call this function more than once, you may end with memory leaks
    > and the last call will be the one acting in the system.
    >
    yes these api's are meant to be called once. I am working on a new
    version where all these function will be multi-instance and hence
    different cpus can support different frequency clipping.
    >
    >
    >> +
    >> +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__ */
    >
    > Another thing, I have the impression that solving the config selection in the
    > header file instead of in .c files is cleaner. If you want to solve the config
    > selection in .c files, better to do so with Makefiles.
    >
    > If you keep the ifdefery ( THERMAL vs. HOTPLUG_CPU vs. CPU_FREQ ) here in the
    > header file, it is easier to read.
    Ok will move them in .h
    >
    >> --
    >> 1.7.1
    >>
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