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Message-ID: <20120207193444.GB8589@besouro>
Date: Tue, 7 Feb 2012 21:34:44 +0200
From: Eduardo Valentin <eduardo.valentin@...com>
To: Amit Kachhap <amit.kachhap@...aro.org>
Cc: eduardo.valentin@...com, linux-pm@...ts.linux-foundation.org,
linaro-dev@...ts.linaro.org, patches@...aro.org,
linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [linux-pm] [RFC PATCH 2/2] thermal: Add generic cpu cooling
implementation
Hello Amit,
On Tue, Feb 07, 2012 at 10:21:15AM -0800, Amit Kachhap wrote:
> Hi eduardo,
>
> Again thanks for the review.
>
> On 7 February 2012 00:25, Eduardo Valentin <eduardo.valentin@...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@...aro.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@...aro.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@...aro.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.
Yeah, well, the idea was to have the max_freq value coming from some
registered callback in your code, not really on cpufreq.
> >
> >> +
> >> + 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@...aro.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.
OK.
Another point, is about the fact that this implementation is clipping the frequency silently.
I mean, by changing the policy.max_freq, we may conflict with what the user defines as max freq.
> >
> >
> >> +
> >> +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
> >>
> >> _______________________________________________
> >> linux-pm mailing list
> >> linux-pm@...ts.linux-foundation.org
> >> https://lists.linuxfoundation.org/mailman/listinfo/linux-pm
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