Re: [PATCH 2/3] devfreq: Add suspend and resume apis

From: MyungJoo Ham
Date: Mon Sep 10 2012 - 05:27:56 EST


> Add devfreq suspend/resume apis for devfreq users. This patch
> supports suspend and resume of devfreq load monitoring, required
> for devices which can idle.
>
> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@xxxxxxxxxx>

Rather than letting device driver be responsible to call devfreq_suspend_device() or devfreq_dev_suspend(),would there be any problems in using pm notifier here? (calling the event handler with DEVFREQ_GOV_SUSPEND/RESUME at pm notifier, stopping them earlier and resuming tham later)

What devfreq-core and devfreq-governors do with suspend/resume is handling the delayed workqueue and it does not have anything to do with device-specific tasks. Thus, having each device driver handle device-specifics with its own pm_ops and having devfreq-core stop sampling seem appropriate.

Putting another burden to each device driver (to call devfreq_suspend/resume_device() at its pm_ops) for an obvious task that could be done at core doesn't seem fair.

Thank you.



Cheers!
MyungJoo

> ---
> drivers/devfreq/devfreq.c | 26 ++++++++++++++++++++++++++
> drivers/devfreq/governor.h | 2 ++
> drivers/devfreq/governor_simpleondemand.c | 9 +++++++++
> include/linux/devfreq.h | 12 ++++++++++++
> 4 files changed, 49 insertions(+)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index be524c7..3a5f126 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -365,6 +365,32 @@ int devfreq_remove_device(struct devfreq *devfreq)
> }
> EXPORT_SYMBOL(devfreq_remove_device);
>
> +/**
> + * devfreq_suspend_device() - Suspend devfreq of a device.
> + * @devfreq the devfreq instance to be suspended
> + */
> +int devfreq_suspend_device(struct devfreq *devfreq)
> +{
> + if (!devfreq)
> + return -EINVAL;
> +
> + return devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_SUSPEND);
> +}
> +EXPORT_SYMBOL(devfreq_suspend_device);
> +
> +/**
> + * devfreq_resume_device() - Resume devfreq of a device.
> + * @devfreq the devfreq instance to be resumed
> + */
> +int devfreq_resume_device(struct devfreq *devfreq)
> +{
> + if (!devfreq)
> + return -EINVAL;
> +
> + return devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_RESUME);
> +}
> +EXPORT_SYMBOL(devfreq_resume_device);
> +
> static ssize_t show_governor(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
> index 4a86af7..7dbbdfc 100644
> --- a/drivers/devfreq/governor.h
> +++ b/drivers/devfreq/governor.h
> @@ -22,6 +22,8 @@
> #define DEVFREQ_GOV_START 0x1
> #define DEVFREQ_GOV_STOP 0x2
> #define DEVFREQ_GOV_INTERVAL 0x3
> +#define DEVFREQ_GOV_SUSPEND 0x4
> +#define DEVFREQ_GOV_RESUME 0x5
>
> /* Caution: devfreq->lock must be locked before calling update_devfreq */
> extern int update_devfreq(struct devfreq *devfreq);
> diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
> index 9802bf9..35b8e8e 100644
> --- a/drivers/devfreq/governor_simpleondemand.c
> +++ b/drivers/devfreq/governor_simpleondemand.c
> @@ -113,6 +113,15 @@ int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
> else
> ret = devfreq_monitor_resume(devfreq);
> break;
> +
> + case DEVFREQ_GOV_SUSPEND:
> + ret = devfreq_monitor_suspend(devfreq);
> + break;
> +
> + case DEVFREQ_GOV_RESUME:
> + ret = devfreq_monitor_resume(devfreq);
> + break;
> +
> default:
> break;
> }
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 7a11c3e..7c7e179 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -155,6 +155,8 @@ extern struct devfreq *devfreq_add_device(struct device *dev,
> const struct devfreq_governor *governor,
> void *data);
> extern int devfreq_remove_device(struct devfreq *devfreq);
> +extern int devfreq_suspend_device(struct devfreq *devfreq);
> +extern int devfreq_resume_device(struct devfreq *devfreq);
>
> /* Helper functions for devfreq user device driver with OPP. */
> extern struct opp *devfreq_recommended_opp(struct device *dev,
> @@ -208,6 +210,16 @@ static int devfreq_remove_device(struct devfreq *devfreq)
> return 0;
> }
>
> +static int devfreq_suspend_device(struct devfreq *devfreq)
> +{
> + return 0;
> +}
> +
> +static int devfreq_resume_device(struct devfreq *devfreq)
> +{
> + return 0;
> +}
> +
> static struct opp *devfreq_recommended_opp(struct device *dev,
> unsigned long *freq, u32 flags)
> {
> --
> 1.7.11.3
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