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

Chanwoo Choi
2020-06-03T03:57:11Z

Hi Andrew-sh.Cheng,

Do you know that why cannot show the patches sent from you on mailing list?

Even if you sent them to linux-pm mailing list, I cannot find
your patches on linux-pm's patchwork[1] and others.
[1] https://patchwork.kernel.org/project/linux-pm/list/

Could you find you patch on mailing list?
Do you use git send-email when you send these patches?

I used the thunderbird tool and gmail for reading the patches.
When I tried to read the original source of this patch,
it looks like that the body of patch is encoded.
I cannot read the plain text of patch body.
- When gmail, use 'Show original'
- When thunderbird, use 'More -> View Source'

If I'm missing something to check this patch,
please let me know. I'll fix my environment.
It is strange situation on my case.

On 6/2/20 8:43 PM, andrew-sh.cheng wrote:
> On Thu, 2020-05-28 at 15:14 +0900, 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'
> Get it.

If you add the blank line before/after of your reply,
it is better to catch your reply. Please add the blank line for me.

>> .
>>
>>> + 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.
> Get it.
> For cpu_freq, I separate it into "unsigned long cpu_curr_freq" and
> "unsigned int cpu_curr_freq_khz"
>>
>>
>>> + 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.
> Get it.
> Will modify them for readability.
>>
>>> +
>>> + 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.
> Get it.
>>
>>
>>> + } 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);
> Get it.
>>
>>> + }
>>> + 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.
> Get it.
>>
>>> +
>>> + 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.
> It is good to change current_freq to curr_freq, but why should it us
> 'unsigned long'?
> I think it is 'unsigned int'.

I think that 'curr_freq' is proper. Yes, it is 'unsigned int'.
When you changing the cpu frequency to device frequency,
recommend to handle them between unsigned int and unsigned long.

>>
>>> + 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'.
> Get it.
>>
>>> + struct cpufreq_policy *policy;
>>> + struct device *cpu_dev;
>>> + unsigned int cpu;
>>> + int ret;
>>> +
>>> + get_online_cpus();
>>
>> Add blank line.
> Get it.
>>
>>> + 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.
>>
>>
> Get it.
>>
>>> + 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.
> Get it.
>>> +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;
>>
> Get it.
>>>
>>> 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;
>> }
> Not fully understanding.
> Do you mean expanding cpufreq_passive_register()?

Yes and rename it for both cpufreq and devfreq.

> I think leave it in function will be with clean for this code segment.

I want that one function handle the notifier register
for both cpufreq and devfreq so that we make it more simply as following:
On the step hanling the governor event, don't need to consider
the type of parent device of devfreq deivce with this style.

case DEVFREQ_GOV_START:
ret = register_notifier(...);
break;
case DEVFREQ_GOV_STOP:
ret = unregister_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)
> Get it.

ditto. As I aboved commented.

>>
>>> 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.
> Get it.
>>
>>> + unsigned int min_freq;
>>> + unsigned int max_freq;
>>> + unsigned int first_cpu;
>>> + struct device *dev;
>>
>> How about changing the name 'dev' to 'cpu_dev'?
> Okay.
>>
>>
>>> + 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;
> Get it.
>>
>>> +
>>> +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.
> Get it.
>>
>>> + * @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