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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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