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    SubjectRE: [PATCH 2/4] thermal: Add generic cpufreq cooling implementation
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    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 ??

    > 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..

    > + 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.

    > +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..

    > +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);

    > +}
    > +
    > +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..

    > + 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..

    > + 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 || ?
    > +
    > + level = notify_cpufreq->cpufreq_state;

    Yes..here it is..please use level/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 ?

    > +
    > + 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.

    > +
    > +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)' ?
    > + 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)' ?
    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.

    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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