On Tue, Mar 23, 2021 at 11:01 PM Chanwoo Choi [off-list ref] wrote:

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

quoted

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

quoted

+
      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

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