Re: [PATCH 06/12] PM / devfreq: Add cpu based scaling support to passive_governor

Chanwoo Choi
2020-05-28T07:07:25Z

Hi Andrew-sh.Cheng,

The exynos-bus.c used the passive governor.
Even if don't make the problem because DEVFREQ_PARENT_DEV is zero,
you need to initialize the parent_type with DEVFREQ_PARENT_DEV as following:

diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
index 8fa8eb541373..1c71c47bc2ac 100644
--- a/drivers/devfreq/exynos-bus.c
+++ b/drivers/devfreq/exynos-bus.c
@@ -369,6 +369,7 @@ static int exynos_bus_profile_init_passive(struct exynos_bus *bus,
return -ENOMEM;

passive_data->parent = parent_devfreq;
+ passive_data->parent_type = DEVFREQ_PARENT_DEV;

/* Add devfreq device for exynos bus with passive governor */
bus->devfreq = devm_devfreq_add_device(dev, profile, DEVFREQ_GOV_PASSIVE,

On 5/28/20 3:14 PM, Chanwoo Choi wrote:
> Hi Andrew-sh.Cheng,
>
> Thanks for your posting. I like this approach absolutely.
> I think that it is necessary. When I developed the embedded product,
> I needed this feature always.
>
> I add the comments on below.
>
>
> And the following email is not valid. So, I dropped this email
> from Cc list.
> Saravana Kannan <skannan@codeaurora.org>
>
>
> On 5/20/20 12:43 PM, Andrew-sh.Cheng wrote:
>> From: Saravana Kannan <skannan@codeaurora.org>
>>
>> Many CPU architectures have caches that can scale independent of the
>> CPUs. Frequency scaling of the caches is necessary to make sure that the
>> cache is not a performance bottleneck that leads to poor performance and
>> power. The same idea applies for RAM/DDR.
>>
>> To achieve this, this patch adds support for cpu based scaling to the
>> passive governor. This is accomplished by taking the current frequency
>> of each CPU frequency domain and then adjust the frequency of the cache
>> (or any devfreq device) based on the frequency of the CPUs. It listens
>> to CPU frequency transition notifiers to keep itself up to date on the
>> current CPU frequency.
>>
>> To decide the frequency of the device, the governor does one of the
>> following:
>> * Derives the optimal devfreq device opp from required-opps property of
>> the parent cpu opp_table.
>>
>> * Scales the device frequency in proportion to the CPU frequency. So, if
>> the CPUs are running at their max frequency, the device runs at its
>> max frequency. If the CPUs are running at their min frequency, the
>> device runs at its min frequency. It is interpolated for frequencies
>> in between.
>>
>> Andrew-sh.Cheng change
>> dev_pm_opp_xlate_opp to dev_pm_opp_xlate_required_opp devfreq->max_freq
>> to devfreq->user_min_freq_req.data.freq.qos->min_freq.target_value
>> for kernel-5.7
>>
>> Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
>> [Sibi: Integrated cpu-freqmap governor into passive_governor]
>> Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
>> Signed-off-by: Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>
>> ---
>> drivers/devfreq/Kconfig | 2 +
>> drivers/devfreq/governor_passive.c | 278 ++++++++++++++++++++++++++++++++++---
>> include/linux/devfreq.h | 40 +++++-
>> 3 files changed, 299 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
>> index 0b1df12e0f21..d9067950af6a 100644
>> --- a/drivers/devfreq/Kconfig
>> +++ b/drivers/devfreq/Kconfig
>> @@ -73,6 +73,8 @@ config DEVFREQ_GOV_PASSIVE
>> device. This governor does not change the frequency by itself
>> through sysfs entries. The passive governor recommends that
>> devfreq device uses the OPP table to get the frequency/voltage.
>> + Alternatively the governor can also be chosen to scale based on
>> + the online CPUs current frequency.
>>
>> comment "DEVFREQ Drivers"
>>
>> diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
>> index 2d67d6c12dce..7dcda02a5bb7 100644
>> --- a/drivers/devfreq/governor_passive.c
>> +++ b/drivers/devfreq/governor_passive.c
>> @@ -8,11 +8,89 @@
>> */
>>
>> #include <linux/module.h>
>> +#include <linux/cpu.h>
>> +#include <linux/cpufreq.h>
>> +#include <linux/cpumask.h>
>> #include <linux/device.h>
>> #include <linux/devfreq.h>
>> +#include <linux/slab.h>
>> #include "governor.h"
>>
>> -static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
>> +static unsigned int xlate_cpufreq_to_devfreq(struct devfreq_passive_data *data,
>
> Need to change 'unsigned int' to 'unsigned long'.
>
>> + unsigned int cpu)
>> +{
>> + unsigned int cpu_min, cpu_max, dev_min, dev_max, cpu_percent, max_state;
>
> Better to define them separately as following and then need to rename
> the variable. Usually, use the 'min_freq' and 'max_freq' word for
> the minimum/maximum frequency.
>
> unsigned int cpu_min_freq, cpu_max_freq, cpu_curr_freq, cpu_percent;
> unsigned long dev_min_freq, dev_max_freq, dev_max_state,
>
> The devfreq used 'unsigned long'. The cpufreq used 'unsigned long'
> and 'unsigned int'. You need to handle them properly.
>
>
>> + struct devfreq_cpu_state *cpu_state = data->cpu_state[cpu];
>> + struct devfreq *devfreq = (struct devfreq *)data->this;
>> + unsigned long *freq_table = devfreq->profile->freq_table;
>
> In this function, use 'cpu' work for cpufreq and use 'dev' for devfreq.
> So, I think 'dev_freq_table' is proper name instead of 'freq_table'
> for the readability.
>
> freq_table -> dev_freq_table
>
>> + struct dev_pm_opp *opp = NULL, *cpu_opp = NULL;
>
> In the get_target_freq_with_devfreq(), use 'p_opp' indicating
> the OPP of parent device. For the consistency, I think that
> use 'p_opp' instead of 'cpu_opp'.
>
>> + unsigned long cpu_freq, freq;
>
> Define the 'cpu_freq' on above with cpu_min_freq/cpu_max_freq definition.
> cpu_freq -> cpu_curr_freq.
>
>> +
>> + if (!cpu_state || cpu_state->first_cpu != cpu ||
>> + !cpu_state->opp_table || !devfreq->opp_table)
>> + return 0;
>> +
>> + cpu_freq = cpu_state->freq * 1000;
>> + cpu_opp = devfreq_recommended_opp(cpu_state->dev, &cpu_freq, 0);
>> + if (IS_ERR(cpu_opp))
>> + return 0;
>> +
>> + opp = dev_pm_opp_xlate_required_opp(cpu_state->opp_table,
>> + devfreq->opp_table, cpu_opp);
>> + dev_pm_opp_put(cpu_opp);
>> +
>> + if (!IS_ERR(opp)) {
>> + freq = dev_pm_opp_get_freq(opp);
>> + dev_pm_opp_put(opp);
>
> Better to add the 'out' goto statement.
> If you use 'goto out', you can reduce the one indentation
> without 'else' statement.
>
>
>> + } else {
>
> As I commented, when dev_pm_opp_xlate_required_opp() return successfully
> , use 'goto out'. We can remove 'else' and then reduce the unneeded indentation.
>
>
>> + /* Use Interpolation if required opps is not available */
>> + cpu_min = cpu_state->min_freq;
>> + cpu_max = cpu_state->max_freq;
>> + cpu_freq = cpu_state->freq;
>> +
>> + if (freq_table) {
>> + /* Get minimum frequency according to sorting order */
>> + max_state = freq_table[devfreq->profile->max_state - 1];
>> + if (freq_table[0] < max_state) {
>> + dev_min = freq_table[0];
>> + dev_max = max_state;
>> + } else {
>> + dev_min = max_state;
>> + dev_max = freq_table[0];
>> + }
>> + } else {
>> + if (devfreq->user_max_freq_req.data.freq.qos->max_freq.target_value
>> + <= devfreq->user_min_freq_req.data.freq.qos->min_freq.target_value)
>> + return 0;
>> + dev_min =
>> + devfreq->user_min_freq_req.data.freq.qos->min_freq.target_value;
>> + dev_max =
>> + devfreq->user_max_freq_req.data.freq.qos->max_freq.target_value;
>
> I think it is not proper to access the variable of pm_qos structure directly.
> Instead of direct access, you have to use the exported PM QoS function such as
> - pm_qos_read_value(devfreq->dev.parent, DEV_PM_QOS_MIN_FREQUENCY);
> - pm_qos_read_value(devfreq->dev.parent, DEV_PM_QOS_MAX_FREQUENCY);
>
>> + }
>> + cpu_percent = ((cpu_freq - cpu_min) * 100) / cpu_max - cpu_min;
>> + freq = dev_min + mult_frac(dev_max - dev_min, cpu_percent, 100);
>> + }
>
>
> I think that you better to add 'out' jump label as following:
>
> out:
>
>> +
>> + return freq;
>> +}
>> +
>> +static int get_target_freq_with_cpufreq(struct devfreq *devfreq,
>> + unsigned long *freq)
>> +{
>> + struct devfreq_passive_data *p_data =
>> + (struct devfreq_passive_data *)devfreq->data;
>> + unsigned int cpu, target_freq = 0;
>
> Need to define 'target_freq' with 'unsigned long' type.
>
>> +
>> + for_each_online_cpu(cpu)
>> + target_freq = max(target_freq,
>> + xlate_cpufreq_to_devfreq(p_data, cpu));
>> +
>> + *freq = target_freq;
>> +
>> + return 0;
>> +}
>> +
>> +static int get_target_freq_with_devfreq(struct devfreq *devfreq,
>> unsigned long *freq)
>> {
>> struct devfreq_passive_data *p_data
>> @@ -23,16 +101,6 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
>> int i, count, ret = 0;
>>
>> /*
>> - * If the devfreq device with passive governor has the specific method
>> - * to determine the next frequency, should use the get_target_freq()
>> - * of struct devfreq_passive_data.
>> - */
>> - if (p_data->get_target_freq) {
>> - ret = p_data->get_target_freq(devfreq, freq);
>> - goto out;
>> - }
>> -
>> - /*
>> * If the parent and passive devfreq device uses the OPP table,
>> * get the next frequency by using the OPP table.
>> */
>> @@ -102,6 +170,37 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
>> return ret;
>> }
>>
>> +static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
>> + unsigned long *freq)
>> +{
>> + struct devfreq_passive_data *p_data =
>> + (struct devfreq_passive_data *)devfreq->data;
>> + int ret;
>> +
>> + /*
>> + * If the devfreq device with passive governor has the specific method
>> + * to determine the next frequency, should use the get_target_freq()
>> + * of struct devfreq_passive_data.
>> + */
>> + if (p_data->get_target_freq)
>> + return p_data->get_target_freq(devfreq, freq);
>> +
>> + switch (p_data->parent_type) {
>> + case DEVFREQ_PARENT_DEV:
>> + ret = get_target_freq_with_devfreq(devfreq, freq);
>> + break;
>> + case CPUFREQ_PARENT_DEV:
>> + ret = get_target_freq_with_cpufreq(devfreq, freq);
>> + break;
>> + default:
>> + ret = -EINVAL;
>> + dev_err(&devfreq->dev, "Invalid parent type\n");
>> + break;
>> + }
>> +
>> + return ret;
>> +}
>> +
>> static int update_devfreq_passive(struct devfreq *devfreq, unsigned long freq)
>> {
>> int ret;
>> @@ -156,6 +255,140 @@ static int devfreq_passive_notifier_call(struct notifier_block *nb,
>> return NOTIFY_DONE;
>> }
>>
>> +static int cpufreq_passive_notifier_call(struct notifier_block *nb,
>> + unsigned long event, void *ptr)
>> +{
>> + struct devfreq_passive_data *data =
>> + container_of(nb, struct devfreq_passive_data, nb);
>> + struct devfreq *devfreq = (struct devfreq *)data->this;
>> + struct devfreq_cpu_state *cpu_state;
>> + struct cpufreq_freqs *freq = ptr;
>
> How about changing 'freq' to 'cpu_freqs'?
>
> In the drivers/cpufreq/cpufreq.c, use 'freqs' name indicating
> the instance of 'struct cpufreq_freqs'. And in order to
> identfy, how about adding 'cpu_' prefix for variable name?
>
>> + unsigned int current_freq;
>
> Need to define curr_freq with 'unsigned long' type
> and better to use 'curr_freq' variable name.
>
>> + int ret;
>> +
>> + if (event != CPUFREQ_POSTCHANGE || !freq ||
>> + !data->cpu_state[freq->policy->cpu])
>> + return 0;
>> +
>> + cpu_state = data->cpu_state[freq->policy->cpu];
>> + if (cpu_state->freq == freq->new)
>> + return 0;
>> +
>> + /* Backup current freq and pre-update cpu state freq*/
>> + current_freq = cpu_state->freq;
>> + cpu_state->freq = freq->new;
>> +
>> + mutex_lock(&devfreq->lock);
>> + ret = update_devfreq(devfreq);
>> + mutex_unlock(&devfreq->lock);
>> + if (ret) {
>> + cpu_state->freq = current_freq;
>> + dev_err(&devfreq->dev, "Couldn't update the frequency.\n");
>> + return ret;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int cpufreq_passive_register(struct devfreq_passive_data **p_data)
>> +{
>> + struct devfreq_passive_data *data = *p_data;
>> + struct devfreq *devfreq = (struct devfreq *)data->this;
>> + struct device *dev = devfreq->dev.parent;
>> + struct opp_table *opp_table = NULL;
>> + struct devfreq_cpu_state *state;
>
> For the readability, I thinkt 'cpu_state' is proper instead of 'state'.
>
>> + struct cpufreq_policy *policy;
>> + struct device *cpu_dev;
>> + unsigned int cpu;
>> + int ret;
>> +
>> + get_online_cpus();
>
> Add blank line.
>
>> + data->nb.notifier_call = cpufreq_passive_notifier_call;
>> + ret = cpufreq_register_notifier(&data->nb,
>> + CPUFREQ_TRANSITION_NOTIFIER);
>> + if (ret) {
>> + dev_err(dev, "Couldn't register cpufreq notifier.\n");
>> + data->nb.notifier_call = NULL;
>> + goto out;
>> + }
>> +
>> + /* Populate devfreq_cpu_state */
>> + for_each_online_cpu(cpu) {
>> + if (data->cpu_state[cpu])
>> + continue;
>> +
>> + policy = cpufreq_cpu_get(cpu);
>
> cpufreq_cpu_get() might return 'NULL'. I think you need to handle
> return value as following:
>
> if (!policy) {
> ret = -EINVAL;
> goto out;
> } else if (PTR_ERR(policy) == -EPROBE_DEFER) {
> goto out;
> } else if (IS_ERR(policy) {
> ret = PTR_ERR(policy);
> dev_err(dev, "Couldn't get the cpufreq_poliy.\n");
> goto out;
> }
>
> If cpufreq_cpu_get() return successfully, to do next.
> It reduces the one indentaion.
>
>
>
>> + if (policy) {
>> + state = kzalloc(sizeof(*state), GFP_KERNEL);
>> + if (!state) {
>> + ret = -ENOMEM;
>> + goto out;
>> + }
>> +
>> + cpu_dev = get_cpu_device(cpu);
>> + if (!cpu_dev) {
>> + dev_err(dev, "Couldn't get cpu device.\n");
>> + ret = -ENODEV;
>> + goto out;
>> + }
>> +
>> + opp_table = dev_pm_opp_get_opp_table(cpu_dev);
>> + if (IS_ERR(devfreq->opp_table)) {
>> + ret = PTR_ERR(opp_table);
>> + goto out;
>> + }
>> +
>> + state->dev = cpu_dev;
>> + state->opp_table = opp_table;
>> + state->first_cpu = cpumask_first(policy->related_cpus);
>> + state->freq = policy->cur;
>> + state->min_freq = policy->cpuinfo.min_freq;
>> + state->max_freq = policy->cpuinfo.max_freq;
>> + data->cpu_state[cpu] = state;
>
> Add blank line.
>
>> + cpufreq_cpu_put(policy);
>> + } else {
>> + ret = -EPROBE_DEFER;
>> + goto out;
>> + }
>> + }
>
> Add blank line.
>
>> +out:
>> + put_online_cpus();
>> + if (ret)
>> + return ret;
>> +
>> + /* Update devfreq */
>> + mutex_lock(&devfreq->lock);
>> + ret = update_devfreq(devfreq);
>> + mutex_unlock(&devfreq->lock);
>> + if (ret)
>> + dev_err(dev, "Couldn't update the frequency.\n");
>> +
>> + return ret;
>> +}
>> +
>> +static int cpufreq_passive_unregister(struct devfreq_passive_data **p_data)
>> +{
>> + struct devfreq_passive_data *data = *p_data;
>> + struct devfreq_cpu_state *cpu_state;
>> + int cpu;
>> +
>> + if (data->nb.notifier_call)
>> + cpufreq_unregister_notifier(&data->nb,
>> + CPUFREQ_TRANSITION_NOTIFIER);
>> +
>> + for_each_possible_cpu(cpu) {
>> + cpu_state = data->cpu_state[cpu];
>> + if (cpu_state) {
>> + if (cpu_state->opp_table)
>> + dev_pm_opp_put_opp_table(cpu_state->opp_table);
>> + kfree(cpu_state);
>> + cpu_state = NULL;
>> + }
>> + }
>> +
>> + return 0;
>> +}
>> +
>> static int devfreq_passive_event_handler(struct devfreq *devfreq,
>> unsigned int event, void *data)
>> {
>> @@ -165,7 +398,7 @@ static int devfreq_passive_event_handler(struct devfreq *devfreq,
>> struct notifier_block *nb = &p_data->nb;
>> int ret = 0;
>>
>> - if (!parent)
>> + if (p_data->parent_type == DEVFREQ_PARENT_DEV && !parent)
>> return -EPROBE_DEFER;
>
> If you modify the devfreq_passive_event_handler() as following,
> you can move this condition for DEVFREQ_PARENT_DEV into
> (register|unregister)_parent_dev_notifier.
>
> switch (event) {
> case DEVFREQ_GOV_START:
> ret = register_parent_dev_notifier(p_data);
> break;
> case DEVFREQ_GOV_STOP:
> ret = unregister_parent_dev_notifier(p_data);
> break;
> default:
> ret = -EINVAL;
> break;
> }
>
> return ret;
>
>>
>> switch (event) {
>> @@ -173,13 +406,24 @@ static int devfreq_passive_event_handler(struct devfreq *devfreq,
>> if (!p_data->this)
>> p_data->this = devfreq;
>>
>> - nb->notifier_call = devfreq_passive_notifier_call;
>> - ret = devfreq_register_notifier(parent, nb,
>> - DEVFREQ_TRANSITION_NOTIFIER);
>> + if (p_data->parent_type == DEVFREQ_PARENT_DEV) {
>> + nb->notifier_call = devfreq_passive_notifier_call;
>> + ret = devfreq_register_notifier(parent, nb,
>> + DEVFREQ_TRANSITION_NOTIFIER);
>> + } else if (p_data->parent_type == CPUFREQ_PARENT_DEV) {
>> + ret = cpufreq_passive_register(&p_data);
>
> I think that we better to collect the code related to notifier registration
> into one function like devfreq_pass_register_notifier() instead of
> cpufreq_passive_register() as following: I think it is more simple and readable.
>
> If you have more proper function name of register_parent_dev_notifier,
> please give your opinion.
>
>
> int register_parent_dev_notifier(struct devfreq_passive_data **p_data)
> switch (p_data->parent_type) {
> case DEVFREQ_PARENT_DEV:
> nb->notifier_call = devfreq_passive_notifier_call;
> ret = devfreq_register_notifier(parent, nb,
> break;
> case CPUFREQ_PARENT_DEV:
> cpufreq_register_notifier(...)
> ...
> break;
> }
>
>
>> + } else {
>> + ret = -EINVAL;
>> + }
>> break;
>> case DEVFREQ_GOV_STOP:
>> - WARN_ON(devfreq_unregister_notifier(parent, nb,
>> - DEVFREQ_TRANSITION_NOTIFIER));
>> + if (p_data->parent_type == DEVFREQ_PARENT_DEV)
>> + WARN_ON(devfreq_unregister_notifier(parent, nb,
>> + DEVFREQ_TRANSITION_NOTIFIER));
>> + else if (p_data->parent_type == CPUFREQ_PARENT_DEV)
>> + cpufreq_passive_unregister(&p_data);
>> + else
>> + ret = -EINVAL;
>
> ditto. unregister_parent_dev_notifier(struct devfreq_passive_data **p_data)
>
>> break;
>> default:
>> break;
>> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
>> index a4b19d593151..04ce576fd6f1 100644
>> --- a/include/linux/devfreq.h
>> +++ b/include/linux/devfreq.h
>> @@ -278,6 +278,32 @@ struct devfreq_simple_ondemand_data {
>>
>> #if IS_ENABLED(CONFIG_DEVFREQ_GOV_PASSIVE)
>> /**
>> + * struct devfreq_cpu_state - holds the per-cpu state
>> + * @freq: the current frequency of the cpu.
>> + * @min_freq: the min frequency of the cpu.
>> + * @max_freq: the max frequency of the cpu.
>> + * @first_cpu: the cpumask of the first cpu of a policy.
>> + * @dev: reference to cpu device.
>> + * @opp_table: reference to cpu opp table.
>> + *
>> + * This structure stores the required cpu_state of a cpu.
>> + * This is auto-populated by the governor.
>> + */
>> +struct devfreq_cpu_state {> + unsigned int freq;
>
> It is better to change from 'freq' to 'curr_freq'
> for more correct expression.
>
>> + unsigned int min_freq;
>> + unsigned int max_freq;
>> + unsigned int first_cpu;
>> + struct device *dev;
>
> How about changing the name 'dev' to 'cpu_dev'?
>
>
>> + struct opp_table *opp_table;
>> +};
>
> devfreq_cpu_state is only handled by within driver/devfreq/governor_passive.c.
>
> So, you can move it into drivers/devfreq/governor_passive.c
> and just add the definition into include/linux/devfreq.h as following:
> It is able to prevent the access of variable of 'struct devfreq_cpu_state'
> outside.
>
> struct devfreq_cpu_state;
>
>> +
>> +enum devfreq_parent_dev_type {
>> + DEVFREQ_PARENT_DEV,
>> + CPUFREQ_PARENT_DEV,
>> +};
>> +
>> +/**
>> * struct devfreq_passive_data - ``void *data`` fed to struct devfreq
>> * and devfreq_add_device
>> * @parent: the devfreq instance of parent device.
>> @@ -288,13 +314,15 @@ struct devfreq_simple_ondemand_data {
>> * using governors except for passive governor.
>> * If the devfreq device has the specific method to decide
>> * the next frequency, should use this callback.
>> - * @this: the devfreq instance of own device.
>> - * @nb: the notifier block for DEVFREQ_TRANSITION_NOTIFIER list
>> + * @parent_type parent type of the device
>
> Need to add ':' at the end of word. -> "parent_type:".
>
>> + * @this: the devfreq instance of own device.
>> + * @nb: the notifier block for DEVFREQ_TRANSITION_NOTIFIER list
>
> I knew that you make them with same indentation.
> But, actually, it is not related to this patch like clean-up code.
> Even if it is not pretty, you better to don't touch 'this' and 'nb' indentaion.
>
>> + * @cpu_state: the state min/max/current frequency of all online cpu's
>> *
>> * The devfreq_passive_data have to set the devfreq instance of parent
>> * device with governors except for the passive governor. But, don't need to
>> - * initialize the 'this' and 'nb' field because the devfreq core will handle
>> - * them.
>> + * initialize the 'this', 'nb' and 'cpu_state' field because the devfreq core
>> + * will handle them.
>> */
>> struct devfreq_passive_data {
>> /* Should set the devfreq instance of parent device */
>> @@ -303,9 +331,13 @@ struct devfreq_passive_data {
>> /* Optional callback to decide the next frequency of passvice device */
>> int (*get_target_freq)(struct devfreq *this, unsigned long *freq);
>>
>> + /* Should set the type of parent device */
>> + enum devfreq_parent_dev_type parent_type;
>> +
>> /* For passive governor's internal use. Don't need to set them */
>> struct devfreq *this;
>> struct notifier_block nb;
>> + struct devfreq_cpu_state *cpu_state[NR_CPUS];
>> };
>> #endif
>>
>>
>
>

--
Best Regards,
Chanwoo Choi
Samsung Electronics