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Date: Wed, 03 Apr 2013 11:16:14 -0700
From: Kevin Hilman <khilman@...aro.org>
To: Rajagopal Venkat <rajagopal.venkat@...aro.org>
Cc: myungjoo.ham@...sung.com, rjw@...k.pl,
Alan Stern <stern@...land.harvard.edu>, patches@...aro.org,
linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] PM / devfreq: tie suspend/resume to runtime-pm
Rajagopal Venkat <rajagopal.venkat@...aro.org> writes:
> Devfreq core suspend/resume of a device is explicitly handled
> by devfreq driver through devfreq_suspend_device() and
> devfreq_resume_device() apis typically called from runtime
> suspend/resume callbacks. This patch aims to take away this
> from devfreq drivers and handle it from runtime-pm core. So
> that device devfreq core suspend/resume is automatically done
> with runtime pm suspend/resume. The devfreq drivers shouldn't
> be concerned on when to suspend/resume the devfreq.
The terminology is a bit confusing here since you're mixing runtime
suspend/resume and just suspend/resume. AFAICT, this patch is only
handling devfreq in the runtime PM core, correct?
Also, how does this work when multiple devices may be using the same
devfreq instance? Using this patch, it looks like the devfreq governor
will be shutdown as soon as the first device runtime suspends, right?
> This patch is targeted to handle devfreq core load monitoring
> suspend/resume only. Not the actual hardware itself. All the
> resources like clocks and regulators must still be handled by
> devfreq driver using runtime-pm. The sequence of devfreq and
^^^^^^^
devfreq driver? Did you mean device driver?
Kevin
> device runtime suspend/resume is,
>
> pm_runtime_suspend(dev) will first suspend device devfreq
> (if available) before device is suspended to ensure devfreq load
> monitoring is stopped and no device resources like clocks are
> accessed while device suspend is in progress.
>
> pm_runtime_resume(dev) will resume device devfreq(if available)
> after device is resumed to ensure device resources like clocks
> are ready for use.
>
> As devfreq suspend/resume is done automatically from runtime-pm,
> this patch removes the existing devfreq_suspend_device() and
> devfreq_resume_device() apis.
>
> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@...aro.org>
> ---
> drivers/base/power/runtime.c | 21 ++++++++++++-
> drivers/devfreq/devfreq.c | 69 +++++++++++++++++++++++++++++++++++++++---
> include/linux/devfreq.h | 18 +++--------
> include/linux/pm.h | 2 ++
> 4 files changed, 91 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> index 3148b10..2438abc 100644
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -11,6 +11,7 @@
> #include <linux/export.h>
> #include <linux/pm_runtime.h>
> #include <trace/events/rpm.h>
> +#include <linux/devfreq.h>
> #include "power.h"
>
> static int rpm_resume(struct device *dev, int rpmflags);
> @@ -406,6 +407,14 @@ static int rpm_suspend(struct device *dev, int rpmflags)
>
> __update_runtime_status(dev, RPM_SUSPENDING);
>
> + /*
> + * Try suspending devfreq before device is runtime suspended.
> + * It wouldn't make sense to continue devfreq load monitoring
> + * when device is runtime suspended.
> + */
> + if (dev->power.devfreq && dev->power.devfreq->runtime_suspend)
> + dev->power.devfreq->runtime_suspend(dev);
> +
> if (dev->pm_domain)
> callback = dev->pm_domain->ops.runtime_suspend;
> else if (dev->type && dev->type->pm)
> @@ -421,8 +430,12 @@ static int rpm_suspend(struct device *dev, int rpmflags)
> callback = dev->driver->pm->runtime_suspend;
>
> retval = rpm_callback(callback, dev);
> - if (retval)
> + if (retval) {
> + /* Resume back devfreq on device suspend failure */
> + if (dev->power.devfreq && dev->power.devfreq->runtime_resume)
> + dev->power.devfreq->runtime_resume(dev);
> goto fail;
> + }
>
> no_callback:
> __update_runtime_status(dev, RPM_SUSPENDED);
> @@ -661,6 +674,12 @@ static int rpm_resume(struct device *dev, int rpmflags)
> __update_runtime_status(dev, RPM_ACTIVE);
> if (parent)
> atomic_inc(&parent->power.child_count);
> + /*
> + * Resume devfreq after runtime resume sequence to ensure
> + * device resources are available for devfreq load monitoring.
> + */
> + if (dev->power.devfreq && dev->power.devfreq->runtime_resume)
> + dev->power.devfreq->runtime_resume(dev);
> }
> wake_up_all(&dev->power.wait_queue);
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 44c4079..b8dab0d 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -25,6 +25,7 @@
> #include <linux/list.h>
> #include <linux/printk.h>
> #include <linux/hrtimer.h>
> +#include <linux/pm_runtime.h>
> #include "governor.h"
>
> static struct class *devfreq_class;
> @@ -42,6 +43,9 @@ static LIST_HEAD(devfreq_governor_list);
> static LIST_HEAD(devfreq_list);
> static DEFINE_MUTEX(devfreq_list_lock);
>
> +static void devfreq_runtime_suspend(struct device *dev);
> +static void devfreq_runtime_resume(struct device *dev);
> +
> /**
> * find_device_devfreq() - find devfreq struct using device pointer
> * @dev: device pointer used to lookup device devfreq.
> @@ -387,6 +391,8 @@ static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
> */
> static void _remove_devfreq(struct devfreq *devfreq, bool skip)
> {
> + unsigned long flags;
> +
> mutex_lock(&devfreq_list_lock);
> if (IS_ERR(find_device_devfreq(devfreq->dev.parent))) {
> mutex_unlock(&devfreq_list_lock);
> @@ -400,6 +406,10 @@ static void _remove_devfreq(struct devfreq *devfreq, bool skip)
> devfreq->governor->event_handler(devfreq,
> DEVFREQ_GOV_STOP, NULL);
>
> + spin_lock_irqsave(&devfreq->dev.parent->power.lock, flags);
> + devfreq->dev.parent->power.devfreq = NULL;
> + spin_unlock_irqrestore(&devfreq->dev.parent->power.lock, flags);
> +
> if (devfreq->profile->exit)
> devfreq->profile->exit(devfreq->dev.parent);
>
> @@ -442,6 +452,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
> {
> struct devfreq *devfreq;
> struct devfreq_governor *governor;
> + unsigned long flags;
> int err = 0;
>
> if (!dev || !profile || !governor_name) {
> @@ -476,6 +487,12 @@ struct devfreq *devfreq_add_device(struct device *dev,
> devfreq->previous_freq = profile->initial_freq;
> devfreq->data = data;
> devfreq->nb.notifier_call = devfreq_notifier_call;
> + devfreq->runtime_suspend = devfreq_runtime_suspend;
> + devfreq->runtime_resume = devfreq_runtime_resume;
> + spin_lock_irqsave(&dev->power.lock, flags);
> + dev->power.devfreq = devfreq;
> + spin_unlock_irqrestore(&dev->power.lock, flags);
> +
>
> devfreq->trans_table = devm_kzalloc(dev, sizeof(unsigned int) *
> devfreq->profile->max_state *
> @@ -549,7 +566,7 @@ EXPORT_SYMBOL(devfreq_remove_device);
> * (e.g., runtime_suspend, suspend) of the device driver that
> * holds the devfreq.
> */
> -int devfreq_suspend_device(struct devfreq *devfreq)
> +static int devfreq_suspend_device(struct devfreq *devfreq)
> {
> if (!devfreq)
> return -EINVAL;
> @@ -560,7 +577,6 @@ int devfreq_suspend_device(struct devfreq *devfreq)
> return devfreq->governor->event_handler(devfreq,
> DEVFREQ_GOV_SUSPEND, NULL);
> }
> -EXPORT_SYMBOL(devfreq_suspend_device);
>
> /**
> * devfreq_resume_device() - Resume devfreq of a device.
> @@ -570,7 +586,7 @@ EXPORT_SYMBOL(devfreq_suspend_device);
> * (e.g., runtime_resume, resume) of the device driver that
> * holds the devfreq.
> */
> -int devfreq_resume_device(struct devfreq *devfreq)
> +static int devfreq_resume_device(struct devfreq *devfreq)
> {
> if (!devfreq)
> return -EINVAL;
> @@ -581,7 +597,52 @@ int devfreq_resume_device(struct devfreq *devfreq)
> return devfreq->governor->event_handler(devfreq,
> DEVFREQ_GOV_RESUME, NULL);
> }
> -EXPORT_SYMBOL(devfreq_resume_device);
> +
> +/**
> + * devfreq_runtime_suspend() - Suspend devfreq of a device.
> + * @dev: the device associated with devfreq
> + *
> + * This function is intended to be called by the runtime-pm
> + * core when the device associated with devfreq is
> + * runtime suspended.
> + */
> +static void devfreq_runtime_suspend(struct device *dev)
> +{
> + struct devfreq *devfreq;
> + int err;
> +
> + mutex_lock(&devfreq_list_lock);
> + devfreq = find_device_devfreq(dev);
> + mutex_unlock(&devfreq_list_lock);
> +
> + err = devfreq_suspend_device(devfreq);
> + if (err)
> + dev_err(dev, "devfreq runtime suspend failed with (%d) error\n",
> + err);
> +}
> +
> +/**
> + * devfreq_runtime_resume() - Resume devfreq of a device.
> + * @dev: the device associated with devfreq
> + *
> + * This function is intended to be called by the runtime-pm
> + * core when the device associated with devfreq is
> + * runtime resumed.
> + */
> +static void devfreq_runtime_resume(struct device *dev)
> +{
> + struct devfreq *devfreq;
> + int err;
> +
> + mutex_lock(&devfreq_list_lock);
> + devfreq = find_device_devfreq(dev);
> + mutex_unlock(&devfreq_list_lock);
> +
> + err = devfreq_resume_device(devfreq);
> + if (err)
> + dev_err(dev, "devfreq runtime resume failed with (%d) error\n",
> + err);
> +}
>
> /**
> * devfreq_add_governor() - Add devfreq governor
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 5f1ab92..669368b 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -140,6 +140,8 @@ struct devfreq_governor {
> * @trans_table: Statistics of devfreq transitions
> * @time_in_state: Statistics of devfreq states
> * @last_stat_updated: The last time stat updated
> + * @runtime_suspend: func to runtime suspend devfreq from runtime core
> + * @runtime_resume: func to runtime resume devfreq from runtime core
> *
> * This structure stores the devfreq information for a give device.
> *
> @@ -173,6 +175,8 @@ struct devfreq {
> unsigned int *trans_table;
> unsigned long *time_in_state;
> unsigned long last_stat_updated;
> + void (*runtime_suspend)(struct device *dev);
> + void (*runtime_resume)(struct device *dev);
> };
>
> #if defined(CONFIG_PM_DEVFREQ)
> @@ -182,10 +186,6 @@ extern struct devfreq *devfreq_add_device(struct device *dev,
> void *data);
> extern int devfreq_remove_device(struct devfreq *devfreq);
>
> -/* Supposed to be called by PM_SLEEP/PM_RUNTIME callbacks */
> -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,
> unsigned long *freq, u32 flags);
> @@ -228,16 +228,6 @@ static inline int devfreq_remove_device(struct devfreq *devfreq)
> return 0;
> }
>
> -static inline int devfreq_suspend_device(struct devfreq *devfreq)
> -{
> - return 0;
> -}
> -
> -static inline int devfreq_resume_device(struct devfreq *devfreq)
> -{
> - return 0;
> -}
> -
> static inline struct opp *devfreq_recommended_opp(struct device *dev,
> unsigned long *freq, u32 flags)
> {
> diff --git a/include/linux/pm.h b/include/linux/pm.h
> index 03d7bb1..734449c 100644
> --- a/include/linux/pm.h
> +++ b/include/linux/pm.h
> @@ -40,6 +40,7 @@ extern void (*pm_power_off_prepare)(void);
> */
>
> struct device;
> +struct devfreq;
>
> #ifdef CONFIG_PM
> extern const char power_group_name[]; /* = "power" */
> @@ -549,6 +550,7 @@ struct dev_pm_info {
> #endif
> struct pm_subsys_data *subsys_data; /* Owned by the subsystem. */
> struct dev_pm_qos *qos;
> + struct devfreq *devfreq; /* device devfreq */
> };
>
> extern void update_pm_runtime_accounting(struct device *dev);
--
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