[PATCH V8 1/8] PM / devfreq: Add cpu based scaling support to passive_governor
Hsin-Yi Wang
hsinyi at chromium.org
Wed Mar 31 11:46:11 BST 2021
On Thu, Mar 25, 2021 at 3:58 PM Chanwoo Choi <cw00.choi at samsung.com> wrote:
>
> Hi,
>
> You are missing to add these patches to linux-pm mailing list.
> Need to send them to linu-pm ML.
>
> Also, before received this series, I tried to clean-up these patches
> on testing branch[1]. So that I add my comment with my clean-up case.
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/chanwoo/linux.git/log/?h=devfreq-testing-passive-gov
>
> And 'Saravana Kannan <skannan at codeaurora.org>' is wrong email address.
> Please update the email or drop this email.
>
>
> On 3/23/21 8:33 PM, Andrew-sh.Cheng wrote:
> > From: Saravana Kannan <skannan at 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
> > after kernel-5.7
> > Don't return -EINVAL in devfreq_passive_event_handler()
> > since it doesn't handle DEVFREQ_GOV_SUSPEND DEVFREQ_GOV_RESUME cases.
> >
> > Signed-off-by: Saravana Kannan <skannan at codeaurora.org>
> > [Sibi: Integrated cpu-freqmap governor into passive_governor]
> > Signed-off-by: Sibi Sankar <sibis at codeaurora.org>
> > Signed-off-by: Andrew-sh.Cheng <andrew-sh.cheng at mediatek.com>
> > ---
> > drivers/devfreq/Kconfig | 2 +
> > drivers/devfreq/governor_passive.c | 329 +++++++++++++++++++++++++++++++++++--
> > include/linux/devfreq.h | 29 +++-
> > 3 files changed, 342 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> > index 00704efe6398..f56132b0ae64 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 b094132bd20b..9cc57b083839 100644
> > --- a/drivers/devfreq/governor_passive.c
> > +++ b/drivers/devfreq/governor_passive.c
> > @@ -8,11 +8,103 @@
> > */
> >
> > #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,
> > +struct devfreq_cpu_state {
> > + unsigned int curr_freq;
> > + unsigned int min_freq;
> > + unsigned int max_freq;
> > + unsigned int first_cpu;
> > + struct device *cpu_dev;
> > + struct opp_table *opp_table;
> > +};
>
> As I knew, the previous version has the description of structure
> as following: I wan to add the description like below.
>
> And if you have no any objection, I'd like you to order
> the variables as following and use 'dev' instead of 'cpu_dev'
> because this patch use the 'cpu_state->cpu_dev' at the multiple points.
> I think that 'cpu_state->dev' is better than 'cpu_state->cpu_dev'.
> Also, I prefer to use 'cur_freq' instead of 'curr_freq'
> because devfreq subsystem uses 'cur_freq' for expressing the 'current frequency'.
>
> /**
> * struct devfreq_cpu_state - Hold the per-cpu data
> * @dev: reference to cpu device.
> * @first_cpu: the cpumask of the first cpu of a policy.
> * @opp_table: reference to cpu opp table.
> * @cur_freq: the current frequency of the cpu.
> * @min_freq: the min frequency of the cpu.
> * @max_freq: the max frequency of the cpu.
> *
> * This structure stores the required cpu_data of a cpu.
> * This is auto-populated by the governor.
> */
> struct devfreq_cpu_state {
> struct device *dev;
> unsigned int first_cpu;
>
> struct opp_table *opp_table;
> unsigned int cur_freq;
> unsigned int min_freq;
> unsigned int max_freq;
> };
>
>
> > +
> > +static unsigned long xlate_cpufreq_to_devfreq(struct devfreq_passive_data *data,
> > + unsigned int cpu)
> > +{
> > + unsigned int cpu_min_freq, cpu_max_freq, cpu_curr_freq_khz, cpu_percent;
> > + unsigned long dev_min_freq, dev_max_freq, dev_max_state;
> > +
> > + struct devfreq_cpu_state *cpu_state = data->cpu_state[cpu];
> > + struct devfreq *devfreq = (struct devfreq *)data->this;
> > + unsigned long *dev_freq_table = devfreq->profile->freq_table;
> > + struct dev_pm_opp *opp = NULL, *p_opp = NULL;
> > + unsigned long cpu_curr_freq, freq;
> > +
> > + if (!cpu_state || cpu_state->first_cpu != cpu ||
> > + !cpu_state->opp_table || !devfreq->opp_table)
> > + return 0;
> > +
> > + cpu_curr_freq = cpu_state->curr_freq * 1000;
> > + p_opp = devfreq_recommended_opp(cpu_state->cpu_dev, &cpu_curr_freq, 0);
> > + if (IS_ERR(p_opp))
> > + return 0;
> > +
> > + opp = dev_pm_opp_xlate_required_opp(cpu_state->opp_table,
> > + devfreq->opp_table, p_opp);
> > + dev_pm_opp_put(p_opp);
> > +
> > + if (!IS_ERR(opp)) {
> > + freq = dev_pm_opp_get_freq(opp);
> > + dev_pm_opp_put(opp);
> > + goto out;
> > + }
> > +
> > + /* Use Interpolation if required opps is not available */
> > + cpu_min_freq = cpu_state->min_freq;
> > + cpu_max_freq = cpu_state->max_freq;
> > + cpu_curr_freq_khz = cpu_state->curr_freq;
> > +
> > + if (dev_freq_table) {
> > + /* Get minimum frequency according to sorting order */
> > + dev_max_state = dev_freq_table[devfreq->profile->max_state - 1];
> > + if (dev_freq_table[0] < dev_max_state) {
> > + dev_min_freq = dev_freq_table[0];
> > + dev_max_freq = dev_max_state;
> > + } else {
> > + dev_min_freq = dev_max_state;
> > + dev_max_freq = dev_freq_table[0];
> > + }
> > + } else {
> > + dev_min_freq = dev_pm_qos_read_value(devfreq->dev.parent,
> > + DEV_PM_QOS_MIN_FREQUENCY);
> > + dev_max_freq = dev_pm_qos_read_value(devfreq->dev.parent,
> > + DEV_PM_QOS_MAX_FREQUENCY);
> > +
> > + if (dev_max_freq <= dev_min_freq)
> > + return 0;
> > + }
> > + cpu_percent = ((cpu_curr_freq_khz - cpu_min_freq) * 100) / cpu_max_freq - cpu_min_freq;
() is missing for denominator?
cpu_percent = ((cpu_curr_freq_khz - cpu_min_freq) * 100) /
(cpu_max_freq - cpu_min_freq);
> > + freq = dev_min_freq + mult_frac(dev_max_freq - dev_min_freq, cpu_percent, 100);
> > +
> > +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;
> > + unsigned long target_freq = 0;
> > +
> > + for_each_online_cpu(cpu)
> > + target_freq = max(target_freq,
> > + xlate_cpufreq_to_devfreq(p_data, cpu));
> > +
> > + *freq = target_freq;
> > +
> > + return 0;
> > +}
>
> As you knew, governor_passive.c was already used
> both 'dev_pm_opp_xlate_required_opp' and 'devfreq_recommended_opp'
> to get the target from OPP. So, I wan to make the common function
> like 'get_taget_freq_by_required_opp' as following:
> If define 'get_taget_freq_by_required_opp' as following,
> it will be used for get_target_freq_with_devfreq().
> After finisied the review of this patch, I'll send the patch[2].
> [2] https://git.kernel.org/pub/scm/linux/kernel/git/chanwoo/linux.git/commit/?h=devfreq-testing-passive-gov&id=101c5a087586ab2b5cf3370166a7e39227ca83cf
>
> For example but this code is not tested,
> static unsigned long get_taget_freq_by_required_opp(struct device *p_dev,
> struct opp_table *p_opp_table,
> struct opp_table *opp_table,
> unsigned long freq)
> {
> struct dev_pm_opp *opp = NULL, *p_opp = NULL;
>
> if (!p_dev || !p_opp_table || !opp_table || !freq)
> return 0;
>
> p_opp = devfreq_recommended_opp(p_dev, &freq, 0);
> if (IS_ERR(p_opp))
> return 0;
>
> opp = dev_pm_opp_xlate_required_opp(p_opp_table, opp_table, p_opp);
> dev_pm_opp_put(p_opp);
>
> if (IS_ERR(opp))
> return 0;
>
> freq = dev_pm_opp_get_freq(opp);
> dev_pm_opp_put(opp);
>
> return freq;
> }
>
> static int get_target_freq_with_cpufreq(struct devfreq *devfreq,
> unsigned long *target_freq)
> {
> struct devfreq_passive_data *p_data =
> (struct devfreq_passive_data *)devfreq->data;
> struct devfreq_cpu_data *cpu_data;
> unsigned long cpu, cpu_cur, cpu_min, cpu_max, cpu_percent;
> unsigned long dev_min, dev_max;
> unsigned long freq = 0;
>
> for_each_online_cpu(cpu) {
> cpu_data = p_data->cpu_data[cpu];
> if (!cpu_data || cpu_data->first_cpu != cpu)
> continue;
>
> /* Get target freq via required opps */
> cpu_cur = cpu_data->cur_freq * HZ_PER_KHZ;
> freq = get_taget_freq_by_required_opp(cpu_data->dev,
> cpu_data->opp_table,
> devfreq->opp_table, cpu_cur);
> if (freq) {
> *target_freq = max(freq, *target_freq);
> continue;
> }
>
> /* Use Interpolation if required opps is not available */
> devfreq_get_freq_range(devfreq, &dev_min, &dev_max);
>
> cpu_min = cpu_data->min_freq;
> cpu_max = cpu_data->max_freq;
> cpu_cur = cpu_data->cur_freq;
>
> cpu_percent = ((cpu_cur - cpu_min) * 100) / cpu_max - cpu_min;
> freq = dev_min + mult_frac(dev_max - dev_min, cpu_percent, 100);
>
> *target_freq = max(freq, *target_freq);
> }
>
> return 0;
> }
>
> > +
> > +static int get_target_freq_with_devfreq(struct devfreq *devfreq,
> > unsigned long *freq)
> > {
> > struct devfreq_passive_data *p_data
> > @@ -23,14 +115,6 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
> > int i, count;
> >
> > /*
> > - * 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);
> > -
> > - /*
> > * If the parent and passive devfreq device uses the OPP table,
> > * get the next frequency by using the OPP table.
> > */
> > @@ -98,6 +182,37 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
> > return 0;
> > }
> >
> > +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 devfreq_passive_notifier_call(struct notifier_block *nb,
> > unsigned long event, void *ptr)
> > {
> > @@ -130,16 +245,200 @@ 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 *cpu_freq = ptr;
>
> Use 'freqs' variable name. I prefer to use the same variable name
> for both devfreq_freqs and cpufreq_freqs instance.
>
> > + unsigned int curr_freq;
>
> As I commented above, better to use 'cur_frq' instead of 'curr_freq'
> if there is no any special reason.
>
> > + int ret;
> > +
> > + if (event != CPUFREQ_POSTCHANGE || !cpu_freq ||
> > + !data->cpu_state[cpu_freq->policy->cpu])
> > + return 0;
> > +
> > + cpu_state = data->cpu_state[cpu_freq->policy->cpu];
> > + if (cpu_state->curr_freq == cpu_freq->new)
> > + return 0;
> > +
> > + /* Backup current freq and pre-update cpu state freq*/
>
> I think that this commnet is not critial. So, please drop this comment.
>
> > + curr_freq = cpu_state->curr_freq;
> > + cpu_state->curr_freq = cpu_freq->new;
> > +
> > + mutex_lock(&devfreq->lock);
> > + ret = update_devfreq(devfreq);
>
> I recommend to use 'devfreq_update_target' instead of 'update_devfreq'
> as following:
> devfreq_update_target(devfreq, freqs->new);
>
> > + mutex_unlock(&devfreq->lock);
> > + if (ret) {
> > + cpu_state->curr_freq = curr_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)
>
> In order to keep the consistent style of function name,
> please change the name as following because devfreq defines
> the function name as 'devfreq_regiter_notifier'
> - cpufreq_passive_register -> cpufreq_passive_register_notifier
>
> > +{
> > + 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 *cpu_state;
> > + struct cpufreq_policy *policy;
> > + struct device *cpu_dev;
> > + unsigned int cpu;
> > + int ret;
> > +
> > + get_online_cpus();
> > +
> > + 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 */
>
> Don't need this comment. Please drop it.
>
> > + for_each_online_cpu(cpu) {
> > + if (data->cpu_state[cpu])
> > + continue;
> > +
> > + policy = cpufreq_cpu_get(cpu);
> > + if (!policy) {
> > + ret = -EINVAL;
> > + goto out;
> > + } else if (PTR_ERR(policy) == -EPROBE_DEFER) {
> > + ret = -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;
> > + }
>
> Use dev_err_probe() funciotn to handle hte EPROBE_DEFER.
> It make code more simple.
>
> > +
> > + cpu_state = kzalloc(sizeof(*cpu_state), GFP_KERNEL);
> > + if (!cpu_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;
> > + }
> > +
> > + cpu_state->cpu_dev = cpu_dev;
> > + cpu_state->opp_table = opp_table;
> > + cpu_state->first_cpu = cpumask_first(policy->related_cpus);
> > + cpu_state->curr_freq = policy->cur;
> > + cpu_state->min_freq = policy->cpuinfo.min_freq;
> > + cpu_state->max_freq = policy->cpuinfo.max_freq;
> > + data->cpu_state[cpu] = cpu_state;
> > +
> > + cpufreq_cpu_put(policy);
> > + }
> > +
> > +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)
>
> As I commented above, please change the name as following:
> - cpufreq_passive_unregister -> cpufreq_passive_unregister_notifier
>
> > +{
> > + 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;
> > +}
> > +
> > +int register_parent_dev_notifier(struct devfreq_passive_data **p_data)
> > +{
> > + struct notifier_block *nb = &(*p_data)->nb;
> > + int ret = 0;
> > +
> > + switch ((*p_data)->parent_type) {
> > + case DEVFREQ_PARENT_DEV:
> > + nb->notifier_call = devfreq_passive_notifier_call;
> > + ret = devfreq_register_notifier((struct devfreq *)(*p_data)->parent, nb,
> > + DEVFREQ_TRANSITION_NOTIFIER);
> > + break;
> > + case CPUFREQ_PARENT_DEV:
> > + ret = cpufreq_passive_register(p_data);
> > + break;
> > + default:
> > + ret = -EINVAL;
> > + break;
> > + }
> > + return ret;
> > +}
> > +
> > +int unregister_parent_dev_notifier(struct devfreq_passive_data **p_data)
> > +{
> > + int ret = 0;
> > +
> > + switch ((*p_data)->parent_type) {
> > + case DEVFREQ_PARENT_DEV:
> > + WARN_ON(devfreq_unregister_notifier((struct devfreq *)(*p_data)->parent,
> > + &(*p_data)->nb,
> > + DEVFREQ_TRANSITION_NOTIFIER));
> > + break;
> > + case CPUFREQ_PARENT_DEV:
> > + cpufreq_passive_unregister(p_data);
> > + break;
> > + default:
> > + ret = -EINVAL;
> > + break;
> > + }
> > + return ret;
> > +}
>
> I think that you don't need to define register_parent_dev_notifier
> and unregister_parent_dev_notifier as the separate functions.
>
> Instead of the separate functions, just add the code
> into devfreq_passive_event_handler.
>
>
> > +
> > static int devfreq_passive_event_handler(struct devfreq *devfreq,
> > unsigned int event, void *data)
> > {
> > struct devfreq_passive_data *p_data
> > = (struct devfreq_passive_data *)devfreq->data;
> > struct devfreq *parent = (struct devfreq *)p_data->parent;
> > - struct notifier_block *nb = &p_data->nb;
> > int ret = 0;
> >
> > - if (!parent)
> > + if (p_data->parent_type == DEVFREQ_PARENT_DEV && !parent)
> > return -EPROBE_DEFER;
> >
> > switch (event) {
> > @@ -147,13 +446,11 @@ 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);
> > + ret = register_parent_dev_notifier(&p_data);
> > break;
> > +
> > case DEVFREQ_GOV_STOP:
> > - WARN_ON(devfreq_unregister_notifier(parent, nb,
> > - DEVFREQ_TRANSITION_NOTIFIER));
> > + ret = unregister_parent_dev_notifier(&p_data);
> > break;
> > default:
> > break;
> > diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> > index 26ea0850be9b..e0093b7c805c 100644
> > --- a/include/linux/devfreq.h
> > +++ b/include/linux/devfreq.h
> > @@ -280,6 +280,25 @@ 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;
> > +
> > +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.
> > @@ -290,13 +309,15 @@ 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.
> > + * @parent_type: parent type of the device
> > * @this: the devfreq instance of own device.
> > * @nb: the notifier block for DEVFREQ_TRANSITION_NOTIFIER list
> > + * @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 */
> > @@ -305,9 +326,13 @@ 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
> >
> >
>
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