diff mbox series

[V2,RESEND,3/4] PM / devfreq: bail out early if no freq changes in devfreq_set_target

Message ID 1616484011-26702-4-git-send-email-aisheng.dong@nxp.com
State Superseded
Headers show
Series PM / devfreq: a few small fixes and improvements | expand

Commit Message

Aisheng Dong March 23, 2021, 7:20 a.m. UTC
It's unnecessary to set the same freq again and run notifier calls.

Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
---
 drivers/devfreq/devfreq.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Comments

Dong Aisheng May 19, 2021, 6:51 a.m. UTC | #1
On Tue, Mar 23, 2021 at 11:01 PM Chanwoo Choi <cwchoi00@gmail.com> wrote:
>

> On 21. 3. 23. 오후 4:20, Dong Aisheng wrote:

> > It's unnecessary to set the same freq again and run notifier calls.

> >

> > Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>

> > ---

> >   drivers/devfreq/devfreq.c | 9 ++++++---

> >   1 file changed, 6 insertions(+), 3 deletions(-)

> >

> > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c

> > index 85927bd7ee76..a6ee91dd17bd 100644

> > --- a/drivers/devfreq/devfreq.c

> > +++ b/drivers/devfreq/devfreq.c

> > @@ -352,13 +352,16 @@ static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,

> >   {

> >       struct devfreq_freqs freqs;

> >       unsigned long cur_freq;

> > -     int err = 0;

> > +     int err;

> >

> >       if (devfreq->profile->get_cur_freq)

> >               devfreq->profile->get_cur_freq(devfreq->dev.parent, &cur_freq);

> >       else

> >               cur_freq = devfreq->previous_freq;

> >

> > +     if (new_freq == cur_freq)

> > +             return 0;

>

> cur_freq is one of the OPP frequencies. But, new_freq is calculated from

> governor algorithm. It means that new_freq is not one of the

> frequencies. Actually, it is not efficient.

>

> After devfreq->profile->target() which almost uses

> devfreq_recommended_opp(), new_freq is one of OPP frequencies.

>


Yes, but i feel at least when the desired new_freq is equal to cur_freq
which is the last successfully set rate,  it is sufficient to bail out early as
it's meaningless to re-set the same rate as the last one and notify the
an unchanged rate transition in HW.
Does that make sense?

Regards
Aisheng

> > +

> >       freqs.old = cur_freq;

> >       freqs.new = new_freq;

> >       devfreq_notify_transition(devfreq, &freqs, DEVFREQ_PRECHANGE);

> > @@ -375,7 +378,7 @@ static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,

> >        * and DEVFREQ_POSTCHANGE because for showing the correct frequency

> >        * change order of between devfreq device and passive devfreq device.

> >        */

> > -     if (trace_devfreq_frequency_enabled() && new_freq != cur_freq)

> > +     if (trace_devfreq_frequency_enabled())

> >               trace_devfreq_frequency(devfreq, new_freq, cur_freq);

> >

> >       freqs.new = new_freq;

> > @@ -390,7 +393,7 @@ static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,

> >       if (devfreq->suspend_freq)

> >               devfreq->resume_freq = new_freq;

> >

> > -     return err;

> > +     return 0;

> >   }

> >

> >   /**

> >

>

>

> --

> Best Regards,

> Samsung Electronics

> Chanwoo Choi
diff mbox series

Patch

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 85927bd7ee76..a6ee91dd17bd 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -352,13 +352,16 @@  static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
 {
 	struct devfreq_freqs freqs;
 	unsigned long cur_freq;
-	int err = 0;
+	int err;
 
 	if (devfreq->profile->get_cur_freq)
 		devfreq->profile->get_cur_freq(devfreq->dev.parent, &cur_freq);
 	else
 		cur_freq = devfreq->previous_freq;
 
+	if (new_freq == cur_freq)
+		return 0;
+
 	freqs.old = cur_freq;
 	freqs.new = new_freq;
 	devfreq_notify_transition(devfreq, &freqs, DEVFREQ_PRECHANGE);
@@ -375,7 +378,7 @@  static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
 	 * and DEVFREQ_POSTCHANGE because for showing the correct frequency
 	 * change order of between devfreq device and passive devfreq device.
 	 */
-	if (trace_devfreq_frequency_enabled() && new_freq != cur_freq)
+	if (trace_devfreq_frequency_enabled())
 		trace_devfreq_frequency(devfreq, new_freq, cur_freq);
 
 	freqs.new = new_freq;
@@ -390,7 +393,7 @@  static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
 	if (devfreq->suspend_freq)
 		devfreq->resume_freq = new_freq;
 
-	return err;
+	return 0;
 }
 
 /**