Re: [PATCH 2/4] PM / devfreq: Handle monitor suspend/resume in the devfreq core

From: Chanwoo Choi
Date: Thu Feb 14 2019 - 09:10:41 EST

Hi Matthias,

2019ë 2ì 14ì (ë) ìí 7:16, Matthias Kaehlcke <mka@xxxxxxxxxxxx>ëì ìì:
>
> devfreq expects governors to call devfreq_monitor_suspend/resume()
> in response to DEVFREQ_GOV_SUSPEND/RESUME events. Since the devfreq
> core itself generates these events and invokes the governor's event
> handler the suspend/resume of the load monitoring can be done in the
> common code.
>
> Call devfreq_monitor_suspend/resume() when the governor reports a
> successful handling of DEVFREQ_GOV_SUSPEND/RESUME and remove these
> calls from the simpleondemand and tegra governors. Make
> devfreq_monitor_suspend/resume() static since these functions are now
> only used by the devfreq core.

The devfreq core generates the all events including
DEVFREQ_GOV_START/STOP/INTERVAL.
It is possible to make 'devfreq_monitor_*()' function as the static
instead of exported function.
And call them in devfreq.c as this patch as following:

--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -728,6 +728,8 @@ struct devfreq *devfreq_add_device(struct device *dev,
goto err_init;
}

+ devfreq_monitor_start(devfreq);
+
list_add(&devfreq->node, &devfreq_list);

mutex_unlock(&devfreq_list_lock);
@@ -760,6 +762,7 @@ int devfreq_remove_device(struct devfreq *devfreq)
if (devfreq->governor)
devfreq->governor->event_handler(devfreq,
DEVFREQ_GOV_STOP, NULL);
+ devfreq_monitor_stop(devfreq);
device_unregister(&devfreq->dev);

return 0;
@@ -1259,6 +1262,9 @@ static ssize_t polling_interval_store(struct device *dev,
df->governor->event_handler(df, DEVFREQ_GOV_INTERVAL, &value);
ret = count;

+ if (!ret)
+ devfreq_interval_update(devfreq, (unsigned int *)data);
+
return ret;
}
static DEVICE_ATTR_RW(polling_interval);
diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
index 79efa1e..515fb85 100644
--- a/drivers/devfreq/tegra-devfreq.c
+++ b/drivers/devfreq/tegra-devfreq.c
@@ -580,13 +580,11 @@ static int tegra_governor_event_handler(struct
devfreq *devfreq,

switch (event) {
case DEVFREQ_GOV_START:
- devfreq_monitor_start(devfreq);
tegra_actmon_enable_interrupts(tegra);
break;

case DEVFREQ_GOV_STOP:
tegra_actmon_disable_interrupts(tegra);
- devfreq_monitor_stop(devfreq);
break;

Instead,

If the governor should execute some codes before and after of
DEVFREQ_GOV_SUSPEND, DEVFREQ_GOV_RESUME,
it is impossible to change the order between devfreq_monitor_*() function
and the specific governor in the event_handler callback function of
each governor.

For example, if some govenor requires the following sequencue,
after this patch, it is not possible.

case DEVFREQ_GOV_SUSPEND:
/* execute some code before devfreq_monitor_suspend() */
devfreq_monitor_suspend()
/* execute some code after devfreq_monitor_suspend() */

>
> Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
> ---
> drivers/devfreq/devfreq.c | 18 ++++++++----------
> drivers/devfreq/governor.h | 2 --
> drivers/devfreq/governor_simpleondemand.c | 8 --------
> drivers/devfreq/tegra-devfreq.c | 2 --
> 4 files changed, 8 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 1d3a43f8b3a10..7fab6c4cf719b 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -447,15 +447,13 @@ EXPORT_SYMBOL(devfreq_monitor_stop);
> * devfreq_monitor_suspend() - Suspend load monitoring of a devfreq instance
> * @devfreq: the devfreq instance.
> *
> - * Helper function to suspend devfreq device load monitoing. Function
> - * to be called from governor in response to DEVFREQ_GOV_SUSPEND
> - * event or when polling interval is set to zero.
> + * Helper function to suspend devfreq device load monitoring.
> *
> * Note: Though this function is same as devfreq_monitor_stop(),
> * intentionally kept separate to provide hooks for collecting
> * transition statistics.
> */
> -void devfreq_monitor_suspend(struct devfreq *devfreq)
> +static void devfreq_monitor_suspend(struct devfreq *devfreq)
> {
> mutex_lock(&devfreq->lock);
> if (devfreq->monitor_state != DEVFREQ_MONITOR_RUNNING) {
> @@ -468,17 +466,14 @@ void devfreq_monitor_suspend(struct devfreq *devfreq)
> mutex_unlock(&devfreq->lock);
> cancel_delayed_work_sync(&devfreq->work);
> }
> -EXPORT_SYMBOL(devfreq_monitor_suspend);
>
> /**
> * devfreq_monitor_resume() - Resume load monitoring of a devfreq instance
> * @devfreq: the devfreq instance.
> *
> - * Helper function to resume devfreq device load monitoing. Function
> - * to be called from governor in response to DEVFREQ_GOV_RESUME
> - * event or when polling interval is set to non-zero.
> + * Helper function to resume devfreq device load monitoring.
> */
> -void devfreq_monitor_resume(struct devfreq *devfreq)
> +static void devfreq_monitor_resume(struct devfreq *devfreq)
> {
> unsigned long freq;
>
> @@ -501,7 +496,6 @@ void devfreq_monitor_resume(struct devfreq *devfreq)
> out:
> mutex_unlock(&devfreq->lock);
> }
> -EXPORT_SYMBOL(devfreq_monitor_resume);
>
> /**
> * devfreq_interval_update() - Update device devfreq monitoring interval
> @@ -903,6 +897,8 @@ int devfreq_suspend_device(struct devfreq *devfreq)
> DEVFREQ_GOV_SUSPEND, NULL);
> if (ret)
> return ret;
> +
> + devfreq_monitor_suspend(devfreq);
> }
>
> if (devfreq->suspend_freq) {
> @@ -944,6 +940,8 @@ int devfreq_resume_device(struct devfreq *devfreq)
> DEVFREQ_GOV_RESUME, NULL);
> if (ret)
> return ret;
> +
> + devfreq_monitor_resume(devfreq);
> }
>
> return 0;
> diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
> index f53339ca610fc..d136792c0cc91 100644
> --- a/drivers/devfreq/governor.h
> +++ b/drivers/devfreq/governor.h
> @@ -59,8 +59,6 @@ struct devfreq_governor {
>
> extern void devfreq_monitor_start(struct devfreq *devfreq);
> extern void devfreq_monitor_stop(struct devfreq *devfreq);
> -extern void devfreq_monitor_suspend(struct devfreq *devfreq);
> -extern void devfreq_monitor_resume(struct devfreq *devfreq);
> extern void devfreq_interval_update(struct devfreq *devfreq,
> unsigned int *delay);
>
> diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
> index c0417f0e081e0..52eb0c734b312 100644
> --- a/drivers/devfreq/governor_simpleondemand.c
> +++ b/drivers/devfreq/governor_simpleondemand.c
> @@ -103,14 +103,6 @@ static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
> devfreq_interval_update(devfreq, (unsigned int *)data);
> break;
>
> - case DEVFREQ_GOV_SUSPEND:
> - devfreq_monitor_suspend(devfreq);
> - break;
> -
> - case DEVFREQ_GOV_RESUME:
> - devfreq_monitor_resume(devfreq);
> - break;
> -
> default:
> break;
> }
> diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
> index c59d2eee5d309..79efa1e51bd06 100644
> --- a/drivers/devfreq/tegra-devfreq.c
> +++ b/drivers/devfreq/tegra-devfreq.c
> @@ -591,11 +591,9 @@ static int tegra_governor_event_handler(struct devfreq *devfreq,
>
> case DEVFREQ_GOV_SUSPEND:
> tegra_actmon_disable_interrupts(tegra);
> - devfreq_monitor_suspend(devfreq);
> break;
>
> case DEVFREQ_GOV_RESUME:
> - devfreq_monitor_resume(devfreq);
> tegra_actmon_enable_interrupts(tegra);
> break;
> }
> --
> 2.20.1.791.gb4d0f1c61a-goog
>


--
Best Regards,
Chanwoo Choi