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SubjectRe: [PATCH 1/4] PM / devfreq: Track overall load monitor state instead of 'stop_polling'
Hi Matthias,

2019년 2월 14일 (목) 오후 7:16, Matthias Kaehlcke <mka@chromium.org>님이 작성:
>
> The field ->stop_polling indicates whether load monitoring should be/is
> stopped, it is set in devfreq_monitor_suspend(). Change the variable to
> hold the general state of load monitoring (stopped, running, suspended).
> Besides improving readability of conditions involving the field and this
> prepares the terrain for moving some duplicated code from the governors
> into the devfreq core.
>
> Hold the devfreq lock in devfreq_monitor_start/stop() to ensure proper
> synchronization.

IMHO, I'm not sure that there are any benefits changing
from 'stop_polling' to 'monitor_state'. I have no objections
if Myungjoo confirms it.

And I agree to move the initialization of work under if statement
according to the value of polling_ms variable in devfreq_monitor_start().

>
> Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
> ---
> drivers/devfreq/devfreq.c | 34 +++++++++++++++++++++++++---------
> include/linux/devfreq.h | 4 ++--
> 2 files changed, 27 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 0ae3de76833b7..1d3a43f8b3a10 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -29,6 +29,10 @@
> #include <linux/of.h>
> #include "governor.h"
>
> +#define DEVFREQ_MONITOR_STOPPED 0
> +#define DEVFREQ_MONITOR_RUNNING 1
> +#define DEVFREQ_MONITOR_SUSPENDED 2
> +
> static struct class *devfreq_class;
>
> /*
> @@ -407,10 +411,17 @@ static void devfreq_monitor(struct work_struct *work)
> */
> void devfreq_monitor_start(struct devfreq *devfreq)
> {
> - INIT_DEFERRABLE_WORK(&devfreq->work, devfreq_monitor);
> - if (devfreq->profile->polling_ms)
> + mutex_lock(&devfreq->lock);
> +
> + if (devfreq->profile->polling_ms) {
> + INIT_DEFERRABLE_WORK(&devfreq->work, devfreq_monitor);
> queue_delayed_work(devfreq_wq, &devfreq->work,
> msecs_to_jiffies(devfreq->profile->polling_ms));
> +
> + devfreq->monitor_state = DEVFREQ_MONITOR_RUNNING;
> + }
> +
> + mutex_unlock(&devfreq->lock);
> }
> EXPORT_SYMBOL(devfreq_monitor_start);
>
> @@ -425,6 +436,10 @@ EXPORT_SYMBOL(devfreq_monitor_start);
> void devfreq_monitor_stop(struct devfreq *devfreq)
> {
> cancel_delayed_work_sync(&devfreq->work);
> +
> + mutex_lock(&devfreq->lock);
> + devfreq->monitor_state = DEVFREQ_MONITOR_STOPPED;
> + mutex_unlock(&devfreq->lock);
> }
> EXPORT_SYMBOL(devfreq_monitor_stop);
>
> @@ -443,13 +458,13 @@ EXPORT_SYMBOL(devfreq_monitor_stop);
> void devfreq_monitor_suspend(struct devfreq *devfreq)
> {
> mutex_lock(&devfreq->lock);
> - if (devfreq->stop_polling) {
> + if (devfreq->monitor_state != DEVFREQ_MONITOR_RUNNING) {
> mutex_unlock(&devfreq->lock);
> return;
> }
>
> devfreq_update_status(devfreq, devfreq->previous_freq);
> - devfreq->stop_polling = true;
> + devfreq->monitor_state = DEVFREQ_MONITOR_SUSPENDED;
> mutex_unlock(&devfreq->lock);
> cancel_delayed_work_sync(&devfreq->work);
> }
> @@ -468,7 +483,7 @@ void devfreq_monitor_resume(struct devfreq *devfreq)
> unsigned long freq;
>
> mutex_lock(&devfreq->lock);
> - if (!devfreq->stop_polling)
> + if (devfreq->monitor_state == DEVFREQ_MONITOR_STOPPED)
> goto out;
>
> if (!delayed_work_pending(&devfreq->work) &&
> @@ -477,7 +492,7 @@ void devfreq_monitor_resume(struct devfreq *devfreq)
> msecs_to_jiffies(devfreq->profile->polling_ms));
>
> devfreq->last_stat_updated = jiffies;
> - devfreq->stop_polling = false;
> + devfreq->monitor_state = DEVFREQ_MONITOR_RUNNING;
>
> if (devfreq->profile->get_cur_freq &&
> !devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq))
> @@ -504,13 +519,14 @@ void devfreq_interval_update(struct devfreq *devfreq, unsigned int *delay)
> mutex_lock(&devfreq->lock);
> devfreq->profile->polling_ms = new_delay;
>
> - if (devfreq->stop_polling)
> + if (devfreq->monitor_state == DEVFREQ_MONITOR_SUSPENDED)
> goto out;
>
> /* if new delay is zero, stop polling */
> if (!new_delay) {
> mutex_unlock(&devfreq->lock);
> cancel_delayed_work_sync(&devfreq->work);
> + devfreq->monitor_state == DEVFREQ_MONITOR_STOPPED;
> return;
> }
>
> @@ -526,7 +542,7 @@ void devfreq_interval_update(struct devfreq *devfreq, unsigned int *delay)
> mutex_unlock(&devfreq->lock);
> cancel_delayed_work_sync(&devfreq->work);
> mutex_lock(&devfreq->lock);
> - if (!devfreq->stop_polling)
> + if (devfreq->monitor_state != DEVFREQ_MONITOR_SUSPENDED)
> queue_delayed_work(devfreq_wq, &devfreq->work,
> msecs_to_jiffies(devfreq->profile->polling_ms));
> }
> @@ -1372,7 +1388,7 @@ static ssize_t trans_stat_show(struct device *dev,
> int i, j;
> unsigned int max_state = devfreq->profile->max_state;
>
> - if (!devfreq->stop_polling &&
> + if ((devfreq->monitor_state == DEVFREQ_MONITOR_RUNNING) &&
> devfreq_update_status(devfreq, devfreq->previous_freq))
> return 0;
> if (max_state == 0)
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index fbffa74bfc1bb..0a618bbb8b294 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -130,7 +130,7 @@ struct devfreq_dev_profile {
> * @max_freq: Limit maximum frequency requested by user (0: none)
> * @scaling_min_freq: Limit minimum frequency requested by OPP interface
> * @scaling_max_freq: Limit maximum frequency requested by OPP interface
> - * @stop_polling: devfreq polling status of a device.
> + * @monitor_state: State of the load monitor.
> * @suspend_freq: frequency of a device set during suspend phase.
> * @resume_freq: frequency of a device set in resume phase.
> * @suspend_count: suspend requests counter for a device.
> @@ -168,7 +168,7 @@ struct devfreq {
> unsigned long max_freq;
> unsigned long scaling_min_freq;
> unsigned long scaling_max_freq;
> - bool stop_polling;
> + int monitor_state;
>
> unsigned long suspend_freq;
> unsigned long resume_freq;
> --
> 2.20.1.791.gb4d0f1c61a-goog
>


--
Best Regards,
Chanwoo Choi

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