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