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SubjectRe: [PATCH 2/4] thermal: Add generic cpufreq cooling implementation
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Hi Durgadoss,

Thanks for the detailed review comments.

On 24 February 2012 16:34, R, Durgadoss <durgadoss.r@intel.com> wrote:
> Hi Amit,
>
>> -----Original Message-----
>> From: amit kachhap [mailto:amitdanielk@gmail.com] On Behalf Of Amit Daniel
>> Kachhap
>> Sent: Wednesday, February 22, 2012 3:44 PM
>> To: linux-pm@lists.linux-foundation.org
>> Cc: linux-kernel@vger.kernel.org; mjg59@srcf.ucam.org; linux-
>> acpi@vger.kernel.org; lenb@kernel.org; linaro-dev@lists.linaro.org;
>> amit.kachhap@linaro.org; R, Durgadoss; rob.lee@linaro.org; patches@linaro.org
>> Subject: [PATCH 2/4] thermal: Add generic cpufreq cooling implementation
>>
>> This patch adds support for generic cpu thermal cooling low level
>> implementations using frequency scaling up/down based on the request
>> from user. Different cpu related cooling devices can be registered by the
>
> I believe what you mean by 'user' is another Driver using this code.. right ??
Yes.
>
>> 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. The user of these api's are responsible for
>> passing clipping frequency in percentages.
>>
>> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org>
>> ---
>>  Documentation/thermal/cpu-cooling-api.txt |   40 ++++
>>  drivers/thermal/Kconfig                   |   11 +
>>  drivers/thermal/Makefile                  |    1 +
>>  drivers/thermal/cpu_cooling.c             |  310 +++++++++++++++++++++++++++++
>>  include/linux/cpu_cooling.h               |   54 +++++
>>  5 files changed, 416 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..04de67c
>> --- /dev/null
>> +++ b/Documentation/thermal/cpu-cooling-api.txt
>> @@ -0,0 +1,40 @@
>> +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 point 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-%x". This api can support multiple instance of cpufreq
>> cooling
>> +    devices.
>> +
>> +    tab_ptr: The table containing the percentage of frequency to be clipped
>> for
>> +    each cooling state.
>> +     .freq_clip_pctg: Percentage of frequency to be clipped for each allowed
>> +      cpus.
>> +     .polling_interval: polling interval for this cooling state.
>> +    tab_size: the total number of cooling state.
>
> Although I can understand that the table size is equal to
> the total number of cooling states, it is better to name it 'num_cooling_states'
> (or something) that means what it is..
Yes your idea makes more sense. Will accept it in the next version.
>
>> +    mask_val: all the allowed cpu's where frequency clipping can happen.
>> +
>> +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.
>> 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..298f550
>> --- /dev/null
>> +++ b/drivers/thermal/cpu_cooling.c
>> @@ -0,0 +1,310 @@
>> +/*
>> + *  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
>
> Except the _idr methods, all the code is inside this #ifdef.
> So, I think it is better to add this dependency in Kconfig,
> and leave this code clean w/o many #ifdef's.
ok
>
>> +struct cpufreq_cooling_device {
>> +     int id;
>> +     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;
>> +     struct list_head node;
>> +};
>> +
>> +static LIST_HEAD(cooling_cpufreq_list);
>> +static DEFINE_MUTEX(cooling_cpufreq_lock);
>> +static DEFINE_IDR(cpufreq_idr);
>> +static struct cpufreq_cooling_device *notify_cpufreq;
>
> Please move this after the DEFINE_PER_CPU.
> Hard to notice here..
ok
>
>> +static DEFINE_PER_CPU(unsigned int, max_policy_freq);
>> +#endif /*CONFIG_CPU_FREQ*/
>> +
>> +static int get_idr(struct idr *idr, struct mutex *lock, int *id)
>> +{
>> +     int err;
>> +again:
>> +     if (unlikely(idr_pre_get(idr, GFP_KERNEL) == 0))
>> +             return -ENOMEM;
>> +
>> +     if (lock)
>> +             mutex_lock(lock);
>> +     err = idr_get_new(idr, NULL, id);
>> +     if (lock)
>> +             mutex_unlock(lock);
>> +     if (unlikely(err == -EAGAIN))
>> +             goto again;
>> +     else if (unlikely(err))
>> +             return err;
>> +
>> +     *id = *id & MAX_ID_MASK;
>> +     return 0;
>> +}
>> +
>> +static void release_idr(struct idr *idr, struct mutex *lock, int id)
>> +{
>> +     if (lock)
>> +             mutex_lock(lock);
>> +     idr_remove(idr, id);
>> +     if (lock)
>> +             mutex_unlock(lock);
>> +}
>> +
>> +#ifdef CONFIG_CPU_FREQ
>> +/*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;
>
> Why not just do a return !cpufreq_get_policy(&policy, cpu);
ok
>
>> +}
>> +
>> +static int cpufreq_apply_cooling(struct cpufreq_cooling_device
>> *cpufreq_device,
>> +                             unsigned long cooling_state)
>> +{
>> +     int cpuid, this_cpu = smp_processor_id();
>> +
>> +     if (!is_cpufreq_valid(this_cpu))
>
> You are not using this_cpu anywhere else..so, directly use
> Smp_processor_id() here..
>
Ok agreed.
>> +             return 0;
>> +
>> +     if (cooling_state > cpufreq_device->tab_size)
>> +             return -EINVAL;
>> +
>> +     /*Check if last cooling level is same as current cooling level*/
>
> Use either 'state' or 'level' in comments as well as the variable name
> Makes it easy to read..

Ok, will use state.
>
>> +     if (cpufreq_device->cpufreq_state == cooling_state)
>> +             return 0;
>> +
>> +     cpufreq_device->cpufreq_state = cooling_state;
>> +
>> +     /*cpufreq thermal notifier uses this cpufreq device pointer*/
>> +     notify_cpufreq = cpufreq_device;
>> +
>> +     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 th_pctg = 0, level;
>> +
>> +     if (event != CPUFREQ_ADJUST)
>> +             return 0;
>> +
>> +     if (!notify_cpufreq)
>> +             return 0;
>
> Why not combine both if's with an || ?
Ok
>
>> +
>> +     level = notify_cpufreq->cpufreq_state;
>
> Yes..here it is..please use level/state..
Ok, will use state
>
>> +
>> +     if (level > 0) {
>> +             th_table =
>> +                     &(notify_cpufreq->tab_ptr[level - 1]);
>> +             th_pctg = th_table->freq_clip_pctg;
>> +             max_freq =
>> +             (policy->cpuinfo.max_freq * (100 - th_pctg)) / 100;
>> +
>> +             if (per_cpu(max_policy_freq, policy->cpu) == 0)
>> +                     per_cpu(max_policy_freq, policy->cpu) = policy->max;
>> +     } else {
>> +             if (per_cpu(max_policy_freq, policy->cpu) != 0) {
>> +                     max_freq = per_cpu(max_policy_freq, policy->cpu);
>> +                     per_cpu(max_policy_freq, policy->cpu) = 0;
>> +             } else {
>> +                     max_freq = policy->max;
>> +             }
>> +     }
>> +
>> +     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)
>> +{
>> +     struct cpufreq_cooling_device *cpufreq_device = NULL;
>
> Why assigning NULL ?
yes it is not needed.
>
>> +
>> +     mutex_lock(&cooling_cpufreq_lock);
>> +     list_for_each_entry(cpufreq_device, &cooling_cpufreq_list, node)
>> +             if (cpufreq_device && cpufreq_device->cool_dev == cdev)
>> +                     break;
>> +
>> +     mutex_unlock(&cooling_cpufreq_lock);
>> +     if (!cpufreq_device || cpufreq_device->cool_dev != cdev)
>> +             return -EINVAL;
>> +
>> +     *state = cpufreq_device->tab_size;
>> +     return 0;
>> +}
>
> The above can be simplified this way:
>        int ret = -EINVAL;
>        mutex_lock(&cooling_cpufreq_lock);
>        list_for_each_entry(cpufreq_device, &cooling_cpufreq_list, node)
>                if (cpufreq_device->cool_dev == cdev) {
>                        *state = cpufreq_device->tab_size;
>                        ret = 0;
>                        break;
>                }
>
>        mutex_unlock(&cooling_cpufreq_lock);
>        return ret;
>
> I think the same can be done for the get_ function below..and similar ones
> in the patch 3/4.

Ok accepted.
>
>> +
>> +static int cpufreq_get_cur_state(struct thermal_cooling_device *cdev,
>> +                              unsigned long *state)
>> +{
>> +     struct cpufreq_cooling_device *cpufreq_device = NULL;
>> +
>> +     mutex_lock(&cooling_cpufreq_lock);
>> +     list_for_each_entry(cpufreq_device, &cooling_cpufreq_list, node)
>> +             if (cpufreq_device && cpufreq_device->cool_dev == cdev)
>> +                     break;
>> +
>> +     mutex_unlock(&cooling_cpufreq_lock);
>> +     if (!cpufreq_device || cpufreq_device->cool_dev != cdev)
>> +             return -EINVAL;
>> +     *state = cpufreq_device->cpufreq_state;
>> +     return 0;
>> +}
>> +
>> +/*This cooling may be as PASSIVE/ACTIVE type*/
>> +static int cpufreq_set_cur_state(struct thermal_cooling_device *cdev,
>> +                              unsigned long state)
>> +{
>> +     struct cpufreq_cooling_device *cpufreq_device = NULL;
>> +
>> +     mutex_lock(&cooling_cpufreq_lock);
>> +     list_for_each_entry(cpufreq_device, &cooling_cpufreq_list, node)
>> +             if (cpufreq_device && cpufreq_device->cool_dev == cdev)
>> +                     break;
>> +
>> +     mutex_unlock(&cooling_cpufreq_lock);
>> +     if (!cpufreq_device || cpufreq_device->cool_dev != cdev)
>> +             return -EINVAL;
>> +
>> +     cpufreq_apply_cooling(cpufreq_device, 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;
>> +     struct cpufreq_cooling_device *cpufreq_dev = NULL;
>> +     unsigned int count = 0;
>> +     char dev_name[THERMAL_NAME_LENGTH];
>> +     int ret = 0, id = 0;
>> +
>> +     if (tab_ptr == NULL || tab_size == 0)
>> +             return ERR_PTR(-EINVAL);
>> +
>> +     list_for_each_entry(cpufreq_dev, &cooling_cpufreq_list, node)
>> +             count++;
>> +
>> +     cpufreq_dev =
>> +             kzalloc(sizeof(struct cpufreq_cooling_device), GFP_KERNEL);
>> +
>> +     if (!cpufreq_dev)
>> +             return ERR_PTR(-ENOMEM);
>> +
>> +     cpufreq_dev->tab_ptr = tab_ptr;
>> +     cpufreq_dev->tab_size = tab_size;
>> +     cpufreq_dev->allowed_cpus = mask_val;
>> +
>> +     ret = get_idr(&cpufreq_idr, &cooling_cpufreq_lock, &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, &cooling_cpufreq_lock,
>> +                                             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);
>> +     mutex_unlock(&cooling_cpufreq_lock);
>> +
>> +     if (count == 0)
>> +             cpufreq_register_notifier(&thermal_cpufreq_notifier_block,
>> +                                             CPUFREQ_POLICY_NOTIFIER);
>
> Why do we register only when count is 0 ?
> Or should this be 'if (count > 0)' ?
Count represents the number of cpufreq type cooling devices. So for
the first call of this API , cpufreq_register_notifier is called.
Other call to cpufreq_cooling_register will use the same notifier. May
be using bool flag instead of count variable is better.
>
>> +     return cool_dev;
>> +}
>> +EXPORT_SYMBOL(cpufreq_cooling_register);
>> +
>> +void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
>> +{
>> +     struct cpufreq_cooling_device *cpufreq_dev = NULL;
>> +     unsigned int 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;
>> +             count++;
>> +     }
>> +
>> +     if (!cpufreq_dev || cpufreq_dev->cool_dev != cdev) {
>> +             mutex_unlock(&cooling_cpufreq_lock);
>> +             return;
>> +     }
>> +
>> +     list_del(&cpufreq_dev->node);
>> +     mutex_unlock(&cooling_cpufreq_lock);
>> +
>> +     if (count == 1)
>
> Same here..I do not get the idea behind this..
> Shouldn't this be 'if (count > 0)' ?
Same as above.
>
> In general,
> I would like to see a real driver using these API's. This will help
> everybody to understand the working of these API's much better.
Actually RFC version of the driver is already posted which uses these
api's. (https://lkml.org/lkml/2011/12/21/169). I forgot to add this
link in this patchset.
I will post the new version of the driver shortly.
>
> Thanks,
> Durga
>
>> +             cpufreq_unregister_notifier(&thermal_cpufreq_notifier_block,
>> +                                     CPUFREQ_POLICY_NOTIFIER);
>> +
>> +     thermal_cooling_device_unregister(cpufreq_dev->cool_dev);
>> +     release_idr(&cpufreq_idr, &cooling_cpufreq_lock, cpufreq_dev->id);
>> +     kfree(cpufreq_dev);
>> +}
>> +EXPORT_SYMBOL(cpufreq_cooling_unregister);
>> +#endif /*CONFIG_CPU_FREQ*/
>> diff --git a/include/linux/cpu_cooling.h b/include/linux/cpu_cooling.h
>> new file mode 100644
>> index 0000000..5dc5632
>> --- /dev/null
>> +++ b/include/linux/cpu_cooling.h
>> @@ -0,0 +1,54 @@
>> +/*
>> + *  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;
>> +     unsigned int polling_interval;
>> +};
>> +
>> +#ifdef CONFIG_CPU_FREQ
>> +struct thermal_cooling_device *cpufreq_cooling_register(
>> +     struct freq_pctg_table *tab_ptr, unsigned int tab_size,
>> +     const struct cpumask *mask_val);
>> +
>> +void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev);
>> +#else /*!CONFIG_CPU_FREQ*/
>> +static inline struct thermal_cooling_device *cpufreq_cooling_register(
>> +     struct freq_pctg_table *tab_ptr, unsigned int tab_size,
>> +     const struct cpumask *mask_val)
>> +{
>> +     return NULL;
>> +}
>> +static inline void cpufreq_cooling_unregister(
>> +                             struct thermal_cooling_device *cdev)
>> +{
>> +     return;
>> +}
>> +#endif       /*CONFIG_CPU_FREQ*/
>> +
>> +#endif /* __CPU_COOLING_H__ */
>> --
>> 1.7.1
>
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