[09/11] PM / devfreq: governor: optimize simpleondemand get_target_freq

devfreq_simple_ondemand_data only needs to be initialized once when
calling devm_devfreq_add_device. It's unnecessary to put the data
check logic in the hot path (.get_target_freq()) where it will be
called all the time during polling. Instead, we only check and initialize
it one time during DEVFREQ_GOV_START.

This also helps check data validability in advance during DEVFREQ_GOV_START
rather than checking it later when running .get_target_freq().

Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
---
 drivers/devfreq/governor_simpleondemand.c | 50 +++++++++++++++--------
 1 file changed, 34 insertions(+), 16 deletions(-)

On Wed, Mar 10, 2021 at 12:09 AM Chanwoo Choi <cwchoi00@gmail.com> wrote:
>
> On 21. 3. 9. 오후 9:58, Dong Aisheng wrote:
> > devfreq_simple_ondemand_data only needs to be initialized once when
> > calling devm_devfreq_add_device. It's unnecessary to put the data
> > check logic in the hot path (.get_target_freq()) where it will be
> > called all the time during polling. Instead, we only check and initialize
> > it one time during DEVFREQ_GOV_START.
> >
> > This also helps check data validability in advance during DEVFREQ_GOV_START
> > rather than checking it later when running .get_target_freq().
> >
> > Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
> > ---
> >   drivers/devfreq/governor_simpleondemand.c | 50 +++++++++++++++--------
> >   1 file changed, 34 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
> > index ea287b57cbf3..341eb7e9dc04 100644
> > --- a/drivers/devfreq/governor_simpleondemand.c
> > +++ b/drivers/devfreq/governor_simpleondemand.c
> > @@ -15,15 +15,19 @@
> >   /* Default constants for DevFreq-Simple-Ondemand (DFSO) */
> >   #define DFSO_UPTHRESHOLD    (90)
> >   #define DFSO_DOWNDIFFERENCTIAL      (5)
> > +
> > +static struct devfreq_simple_ondemand_data od_default = {
> > +     .upthreshold = DFSO_UPTHRESHOLD,
> > +     .downdifferential = DFSO_DOWNDIFFERENCTIAL,
> > +};
> > +
> >   static int devfreq_simple_ondemand_func(struct devfreq *df,
> >                                       unsigned long *freq)
> >   {
> >       int err;
> >       struct devfreq_dev_status *stat;
> >       unsigned long long a, b;
> > -     unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD;
> > -     unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL;
> > -     struct devfreq_simple_ondemand_data *data = df->data;
> > +     struct devfreq_simple_ondemand_data *od = df->data;
> >
> >       err = devfreq_update_stats(df);
> >       if (err)
> > @@ -31,16 +35,6 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
> >
> >       stat = &df->last_status;
> >
> > -     if (data) {
> > -             if (data->upthreshold)
> > -                     dfso_upthreshold = data->upthreshold;
> > -             if (data->downdifferential)
> > -                     dfso_downdifferential = data->downdifferential;
> > -     }
> > -     if (dfso_upthreshold > 100 ||
> > -         dfso_upthreshold < dfso_downdifferential)
> > -             return -EINVAL;
> > -
> >       /* Assume MAX if it is going to be divided by zero */
> >       if (stat->total_time == 0) {
> >               *freq = DEVFREQ_MAX_FREQ;
> > @@ -55,7 +49,7 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
> >
> >       /* Set MAX if it's busy enough */
> >       if (stat->busy_time * 100 >
> > -         stat->total_time * dfso_upthreshold) {
> > +         stat->total_time * od->upthreshold) {
> >               *freq = DEVFREQ_MAX_FREQ;
> >               return 0;
> >       }
> > @@ -68,7 +62,7 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
> >
> >       /* Keep the current frequency */
> >       if (stat->busy_time * 100 >
> > -         stat->total_time * (dfso_upthreshold - dfso_downdifferential)) {
> > +         stat->total_time * (od->upthreshold - od->downdifferential)) {
> >               *freq = stat->current_frequency;
> >               return 0;
> >       }
> > @@ -78,17 +72,41 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
> >       a *= stat->current_frequency;
> >       b = div_u64(a, stat->total_time);
> >       b *= 100;
> > -     b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
> > +     b = div_u64(b, (od->upthreshold - od->downdifferential / 2));
> >       *freq = (unsigned long) b;
> >
> >       return 0;
> >   }
> >
> > +static int devfreq_simple_ondemand_check_od(struct devfreq *devfreq)
> > +{
> > +     struct devfreq_simple_ondemand_data *od = devfreq->data;
> > +
> > +     if (od) {
> > +             if (!od->upthreshold)
> > +                     od->upthreshold = DFSO_UPTHRESHOLD;
> > +
> > +             if (!od->downdifferential)
> > +                     od->downdifferential = DFSO_DOWNDIFFERENCTIAL;
> > +
> > +             if (od->upthreshold > 100 ||
> > +                 od->upthreshold < od->downdifferential)
> > +                     return -EINVAL;
> > +     } else {
> > +             od = &od_default;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> >   static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
> >                               unsigned int event, void *data)
> >   {
> >       switch (event) {
> >       case DEVFREQ_GOV_START:
> > +             if (devfreq_simple_ondemand_check_od(devfreq))
> > +                     return -EINVAL;
> > +
> >               return devfreq_monitor_start(devfreq);
> >
> >       case DEVFREQ_GOV_STOP:
> >
>
> I'm editing the upthreshold and downdifferential for exposing them
> via sysfs. So that after my work to expose them via sysfs,
> send the patches if you think that need to do more about them.

Thanks for letting me know..
I can rework after your patch merged.

Regards
Aisheng

>
> [1]
> https://git.kernel.org/pub/scm/linux/kernel/git/chanwoo/linux.git/commit/?h=devfreq-testing&id=dc9e557845c17cee173a6adcc3ae14940da03f44
>
> --
> Best Regards,
> Samsung Electronics
> Chanwoo Choi