Re: [PATCH v6 1/6] thermal: add generic cpufreq cooling implementation

[Zhang Rui <rui.zhang@intel.com>]

On 五, 2012-08-17 at 11:56 +0300, Valentin, Eduardo wrote:
> Hello,

> >>> +
> >>> +
> >>> +1.2 CPU cooling action notifier register/unregister interface
> >>> +1.2.1 int cputherm_register_notifier(struct notifier_block *nb,
> >>> +     unsigned int list)
> >>> +
> >>> +    This interface registers a driver with cpu cooling layer. The driver will
> >>> +    be notified when any cpu cooling action is called.
> >>> +
> >>> +    nb: notifier function to register
> >>> +    list: CPUFREQ_COOLING_START or CPUFREQ_COOLING_STOP
> >>> +
> >>> +1.2.2 int cputherm_unregister_notifier(struct notifier_block *nb,
> >>> +     unsigned int list)
> >>> +
> >>> +    This interface registers a driver with cpu cooling layer. The driver will
> >>> +    be notified when any cpu cooling action is called.
> >>> +
> >>> +    nb: notifier function to register
> >>> +    list: CPUFREQ_COOLING_START or CPUFREQ_COOLING_STOP
> >>
> >> what are these two APIs used for?
> >> I did not see they are used in your patch set, do I miss something?
> > No currently they are not used by my patches. I added them on request
> > from Eduardo and others
> 
> Yeah, this was a suggestion as we didn't really know how the FW part
> would evolve by that time.
> 
> The reasoning is to allow any interested user (in kernel) to be
> notified when max frequency changes.

in this case, the cooling device should be updated.
Say all the target of the thermal_instances of a cooling devices is 0,
which means they want the cpu to run at maximum frequency, when the max
frequency changes, we should set the processor to the new max frequency
as well.
Using notification is not a good idea as user can not handle this
without interacting with the thermal framework.

IMO, we should introduce a new API to handle this, rather than just
notifications to users.

>  Actually, the use case behind
> this is to allow such users to perform some handshaking or stop their
> activities or even change some paramenters, in case the max frequency
> would change.

It is the cooling device driver that notice this change first, and it
should invoke something like thermal_cooling_device_update/rebind() to
tell the thermal framework this change.

>  Ideally it would be possible to nack the cooling
> transition. But that is yet a wider discussion. So far we don't have
> users for this.
> 
yep.
I thought about this before, but I'd prefer to do this when there is a
real user. Or else, we are kind of over-designing here.
how about removing this piece of code for now?

thanks,
rui

> >>
> >>> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> >>> index 7dd8c34..996003b 100644
> >>> --- a/drivers/thermal/Kconfig
> >>> +++ b/drivers/thermal/Kconfig
> >>> @@ -19,6 +19,17 @@ config THERMAL_HWMON
> >>>       depends on HWMON=y || HWMON=THERMAL
> >>>       default y
> >>>
> >>> +config CPU_THERMAL
> >>> +     bool "generic cpu cooling support"
> >>> +     depends on THERMAL && CPU_FREQ
> >>> +     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 here.
> >>> +
> >>>  config SPEAR_THERMAL
> >>>       bool "SPEAr thermal sensor driver"
> >>>       depends on THERMAL
> >>> diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
> >>> index fd9369a..aae59ad 100644
> >>> --- a/drivers/thermal/Makefile
> >>> +++ b/drivers/thermal/Makefile
> >>> @@ -3,5 +3,6 @@
> >>>  #
> >>>
> >>>  obj-$(CONFIG_THERMAL)                += thermal_sys.o
> >>> +obj-$(CONFIG_CPU_THERMAL)            += cpu_cooling.o
> >>>  obj-$(CONFIG_SPEAR_THERMAL)          += spear_thermal.o
> >>>  obj-$(CONFIG_RCAR_THERMAL)   += rcar_thermal.o
> >>> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
> >>> new file mode 100644
> >>> index 0000000..c42e557
> >>> --- /dev/null
> >>> +++ b/drivers/thermal/cpu_cooling.c
> >>> @@ -0,0 +1,512 @@
> >>> +/*
> >>> + *  linux/drivers/thermal/cpu_cooling.c
> >>> + *
> >>> + *  Copyright (C) 2012       Samsung Electronics Co., Ltd(http://www.samsung.com)
> >>> + *  Copyright (C) 2012  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>
> >>> +
> >>> +/**
> >>> + * struct cpufreq_cooling_device
> >>> + * @id: unique integer value corresponding to each cpufreq_cooling_device
> >>> + *   registered.
> >>> + * @cool_dev: thermal_cooling_device pointer to keep track of the the
> >>> + *   egistered cooling device.
> >>> + * @cpufreq_state: integer value representing the current state of cpufreq
> >>> + *   cooling devices.
> >>> + * @cpufreq_val: integer value representing the absolute value of the clipped
> >>> + *   frequency.
> >>> + * @allowed_cpus: all the cpus involved for this cpufreq_cooling_device.
> >>> + * @node: list_head to link all cpufreq_cooling_device together.
> >>> + *
> >>> + * This structure is required for keeping information of each
> >>> + * cpufreq_cooling_device registered as a list whose head is represented by
> >>> + * cooling_cpufreq_list. In order to prevent corruption of this list a
> >>> + * mutex lock cooling_cpufreq_lock is used.
> >>> + */
> >>> +struct cpufreq_cooling_device {
> >>> +     int id;
> >>> +     struct thermal_cooling_device *cool_dev;
> >>> +     unsigned int cpufreq_state;
> >>> +     unsigned int cpufreq_val;
> >>> +     struct cpumask allowed_cpus;
> >>> +     struct list_head node;
> >>> +};
> >>> +static LIST_HEAD(cooling_cpufreq_list);
> >>> +static DEFINE_IDR(cpufreq_idr);
> >>> +
> >>> +static struct mutex cooling_cpufreq_lock;
> >>> +
> >>> +/* notify_table passes value to the CPUFREQ_ADJUST callback function. */
> >>> +#define NOTIFY_INVALID NULL
> >>> +struct cpufreq_cooling_device *notify_device;
> >>> +
> >>> +/* Head of the blocking notifier chain to inform about frequency clamping */
> >>> +static BLOCKING_NOTIFIER_HEAD(cputherm_state_notifier_list);
> >>> +
> >>> +/**
> >>> + * get_idr - function to get a unique id.
> >>> + * @idr: struct idr * handle used to create a id.
> >>> + * @id: int * value generated by this function.
> >>> + */
> >>> +static int get_idr(struct idr *idr, int *id)
> >>> +{
> >>> +     int err;
> >>> +again:
> >>> +     if (unlikely(idr_pre_get(idr, GFP_KERNEL) == 0))
> >>> +             return -ENOMEM;
> >>> +
> >>> +     mutex_lock(&cooling_cpufreq_lock);
> >>> +     err = idr_get_new(idr, NULL, id);
> >>> +     mutex_unlock(&cooling_cpufreq_lock);
> >>> +
> >>> +     if (unlikely(err == -EAGAIN))
> >>> +             goto again;
> >>> +     else if (unlikely(err))
> >>> +             return err;
> >>> +
> >>> +     *id = *id & MAX_ID_MASK;
> >>> +     return 0;
> >>> +}
> >>> +
> >>> +/**
> >>> + * release_idr - function to free the unique id.
> >>> + * @idr: struct idr * handle used for creating the id.
> >>> + * @id: int value representing the unique id.
> >>> + */
> >>> +static void release_idr(struct idr *idr, int id)
> >>> +{
> >>> +     mutex_lock(&cooling_cpufreq_lock);
> >>> +     idr_remove(idr, id);
> >>> +     mutex_unlock(&cooling_cpufreq_lock);
> >>> +}
> >>> +
> >>> +/**
> >>> + * cputherm_register_notifier - Register a notifier with cpu cooling interface.
> >>> + * @nb:      struct notifier_block * with callback info.
> >>> + * @list: integer value for which notification is needed. possible values are
> >>> + *   CPUFREQ_COOLING_START and CPUFREQ_COOLING_STOP.
> >>> + *
> >>> + * This exported function registers a driver with cpu cooling layer. The driver
> >>> + * will be notified when any cpu cooling action is called.
> >>> + */
> >>> +int cputherm_register_notifier(struct notifier_block *nb, unsigned int list)
> >>> +{
> >>> +     int ret = 0;
> >>> +
> >>> +     switch (list) {
> >>> +     case CPUFREQ_COOLING_START:
> >>> +     case CPUFREQ_COOLING_STOP:
> >>> +             ret = blocking_notifier_chain_register(
> >>> +                             &cputherm_state_notifier_list, nb);
> >>> +             break;
> >>> +     default:
> >>> +             ret = -EINVAL;
> >>> +     }
> >>> +     return ret;
> >>> +}
> >>> +EXPORT_SYMBOL(cputherm_register_notifier);
> >>> +
> >>> +/**
> >>> + * cputherm_unregister_notifier - Un-register a notifier.
> >>> + * @nb:      struct notifier_block * with callback info.
> >>> + * @list: integer value for which notification is needed. values possible are
> >>> + *   CPUFREQ_COOLING_START or CPUFREQ_COOLING_STOP.
> >>> + *
> >>> + * This exported function un-registers a driver with cpu cooling layer.
> >>> + */
> >>> +int cputherm_unregister_notifier(struct notifier_block *nb, unsigned int list)
> >>> +{
> >>> +     int ret = 0;
> >>> +
> >>> +     switch (list) {
> >>> +     case CPUFREQ_COOLING_START:
> >>> +     case CPUFREQ_COOLING_STOP:
> >>> +             ret = blocking_notifier_chain_unregister(
> >>> +                             &cputherm_state_notifier_list, nb);
> >>> +             break;
> >>> +     default:
> >>> +             ret = -EINVAL;
> >>> +     }
> >>> +     return ret;
> >>> +}
> >>> +EXPORT_SYMBOL(cputherm_unregister_notifier);
> >>> +
> >>> +/* Below code defines functions to be used for cpufreq as cooling device */
> >>> +
> >>> +/**
> >>> + * is_cpufreq_valid - function to check if a cpu has frequency transition policy.
> >>> + * @cpu: cpu for which check is needed.
> >>> + */
> >>> +static int is_cpufreq_valid(int cpu)
> >>> +{
> >>> +     struct cpufreq_policy policy;
> >>> +     return !cpufreq_get_policy(&policy, cpu);
> >>> +}
> >>> +
> >>> +/**
> >>> + * get_cpu_frequency - get the absolute value of frequency from level.
> >>> + * @cpu: cpu for which frequency is fetched.
> >>> + * @level: level of frequency of the CPU
> >>> + *   e.g level=1 --> 1st MAX FREQ, LEVEL=2 ---> 2nd MAX FREQ, .... etc
> >>> + */
> >>> +static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
> >>> +{
> >>> +     int ret = 0, i = 0;
> >>> +     unsigned long level_index;
> >>> +     bool descend = false;
> >>> +     struct cpufreq_frequency_table *table =
> >>> +                                     cpufreq_frequency_get_table(cpu);
> >>> +     if (!table)
> >>> +             return ret;
> >>> +
> >>> +     while (table[i].frequency != CPUFREQ_TABLE_END) {
> >>> +             if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
> >>> +                     continue;
> >>> +
> >>> +             /*check if table in ascending or descending order*/
> >>> +             if ((table[i + 1].frequency != CPUFREQ_TABLE_END) &&
> >>> +                     (table[i + 1].frequency < table[i].frequency)
> >>> +                     && !descend) {
> >>> +                     descend = true;
> >>> +             }
> >>> +
> >>> +             /*return if level matched and table in descending order*/
> >>> +             if (descend && i == level)
> >>> +                     return table[i].frequency;
> >>> +             i++;
> >>> +     }
> >>> +     i--;
> >>> +
> >>> +     if (level > i || descend)
> >>> +             return ret;
> >>> +     level_index = i - level;
> >>> +
> >>> +     /*Scan the table in reverse order and match the level*/
> >>> +     while (i >= 0) {
> >>> +             if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
> >>> +                     continue;
> >>> +             /*return if level matched*/
> >>> +             if (i == level_index)
> >>> +                     return table[i].frequency;
> >>> +             i--;
> >>> +     }
> >>> +     return ret;
> >>> +}
> >>> +
> >>> +/**
> >>> + * cpufreq_apply_cooling - function to apply frequency clipping.
> >>> + * @cpufreq_device: cpufreq_cooling_device pointer containing frequency
> >>> + *   clipping data.
> >>> + * @cooling_state: value of the cooling state.
> >>> + */
> >>> +static int cpufreq_apply_cooling(struct cpufreq_cooling_device *cpufreq_device,
> >>> +                             unsigned long cooling_state)
> >>> +{
> >>> +     unsigned int event, cpuid, clip_freq;
> >>> +     struct cpumask *maskPtr = &cpufreq_device->allowed_cpus;
> >>> +     unsigned int cpu = cpumask_any(maskPtr);
> >>> +
> >>> +
> >>> +     /* Check if the old cooling action is same as new cooling action */
> >>> +     if (cpufreq_device->cpufreq_state == cooling_state)
> >>> +             return 0;
> >>> +
> >>> +     clip_freq = get_cpu_frequency(cpu, cooling_state);
> >>> +     if (!clip_freq)
> >>> +             return -EINVAL;
> >>> +
> >>> +     cpufreq_device->cpufreq_state = cooling_state;
> >>> +     cpufreq_device->cpufreq_val = clip_freq;
> >>> +     notify_device = cpufreq_device;
> >>> +
> >>> +     if (cooling_state != 0)
> >>> +             event = CPUFREQ_COOLING_START;
> >>> +     else
> >>> +             event = CPUFREQ_COOLING_STOP;
> >>> +
> >>> +     blocking_notifier_call_chain(&cputherm_state_notifier_list,
> >>> +                                             event, &clip_freq);
> >>> +
> >>> +     for_each_cpu(cpuid, maskPtr) {
> >>> +             if (is_cpufreq_valid(cpuid))
> >>> +                     cpufreq_update_policy(cpuid);
> >>> +     }
> >>> +
> >>> +     notify_device = NOTIFY_INVALID;
> >>> +
> >>> +     return 0;
> >>> +}
> >>> +
> >>> +/**
> >>> + * cpufreq_thermal_notifier - notifier callback for cpufreq policy change.
> >>> + * @nb:      struct notifier_block * with callback info.
> >>> + * @event: value showing cpufreq event for which this function invoked.
> >>> + * @data: callback-specific data
> >>> + */
> >>> +static int cpufreq_thermal_notifier(struct notifier_block *nb,
> >>> +                                     unsigned long event, void *data)
> >>> +{
> >>> +     struct cpufreq_policy *policy = data;
> >>> +     unsigned long max_freq = 0;
> >>> +
> >>> +     if (event != CPUFREQ_ADJUST || notify_device == NOTIFY_INVALID)
> >>> +             return 0;
> >>> +
> >>> +     if (cpumask_test_cpu(policy->cpu, &notify_device->allowed_cpus))
> >>> +             max_freq = notify_device->cpufreq_val;
> >>> +
> >>> +     /* Never exceed user_policy.max*/
> >>> +     if (max_freq > policy->user_policy.max)
> >>> +             max_freq = policy->user_policy.max;
> >>> +
> >>> +     if (policy->max != max_freq)
> >>> +             cpufreq_verify_within_limits(policy, 0, max_freq);
> >>> +
> >>> +     return 0;
> >>> +}
> >>> +
> >>> +/*
> >>> + * cpufreq cooling device callback functions are defined below
> >>> + */
> >>> +
> >>> +/**
> >>> + * cpufreq_get_max_state - callback function to get the max cooling state.
> >>> + * @cdev: thermal cooling device pointer.
> >>> + * @state: fill this variable with the max cooling state.
> >>> + */
> >>> +static int cpufreq_get_max_state(struct thermal_cooling_device *cdev,
> >>> +                              unsigned long *state)
> >>> +{
> >>> +     int ret = -EINVAL, i = 0;
> >>> +     struct cpufreq_cooling_device *cpufreq_device;
> >>> +     struct cpumask *maskPtr;
> >>> +     unsigned int cpu;
> >>> +     struct cpufreq_frequency_table *table;
> >>> +
> >>> +     mutex_lock(&cooling_cpufreq_lock);
> >>> +     list_for_each_entry(cpufreq_device, &cooling_cpufreq_list, node) {
> >>> +             if (cpufreq_device && cpufreq_device->cool_dev == cdev)
> >>> +                     break;
> >>> +     }
> >>> +     if (cpufreq_device == NULL)
> >>> +             goto return_get_max_state;
> >>> +
> >>> +     maskPtr = &cpufreq_device->allowed_cpus;
> >>> +     cpu = cpumask_any(maskPtr);
> >>> +     table = cpufreq_frequency_get_table(cpu);
> >>> +     if (!table) {
> >>> +             *state = 0;
> >>> +             ret = 0;
> >>> +             goto return_get_max_state;
> >>> +     }
> >>> +
> >>> +     while (table[i].frequency != CPUFREQ_TABLE_END) {
> >>> +             if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
> >>> +                     continue;
> >>> +             i++;
> >>> +     }
> >>> +     if (i > 0) {
> >>> +             *state = --i;
> >>> +             ret = 0;
> >>> +     }
> >>> +
> >>> +return_get_max_state:
> >>> +     mutex_unlock(&cooling_cpufreq_lock);
> >>> +     return ret;
> >>> +}
> >>> +
> >>> +/**
> >>> + * cpufreq_get_cur_state - callback function to get the current cooling state.
> >>> + * @cdev: thermal cooling device pointer.
> >>> + * @state: fill this variable with the current cooling state.
> >>> + */
> >>> +static int cpufreq_get_cur_state(struct thermal_cooling_device *cdev,
> >>> +                              unsigned long *state)
> >>> +{
> >>> +     int ret = -EINVAL;
> >>> +     struct cpufreq_cooling_device *cpufreq_device;
> >>> +
> >>> +     mutex_lock(&cooling_cpufreq_lock);
> >>> +     list_for_each_entry(cpufreq_device, &cooling_cpufreq_list, node) {
> >>> +             if (cpufreq_device && cpufreq_device->cool_dev == cdev) {
> >>> +                     *state = cpufreq_device->cpufreq_state;
> >>> +                     ret = 0;
> >>> +                     break;
> >>> +             }
> >>> +     }
> >>> +     mutex_unlock(&cooling_cpufreq_lock);
> >>> +
> >>
> >> as cpufreq may be changed in other places, e.g. via sysfs I/F, we should
> >> use the current cpu frequency to get the REAL cooling state, rather than
> >> using a cached value.
> >
> > Yes agreed , I will repost with your suggestion.
> >
> > Thanks,
> > Amit
> >>
> >> thanks,
> >> rui
> >>
> >>
> > --
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> 
> 
> 


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