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Tue, 23 Mar 2021 08:01:57 -0700 (PDT) Subject: Re: [PATCH V2 RESEND 3/4] PM / devfreq: bail out early if no freq changes in devfreq_set_target To: Dong Aisheng , linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: dongas86@gmail.com, kernel@pengutronix.de, shawnguo@kernel.org, linux-imx@nxp.com, linux-kernel@vger.kernel.org, myungjoo.ham@samsung.com, kyungmin.park@samsung.com, cw00.choi@samsung.com, abel.vesa@nxp.com References: <1616484011-26702-1-git-send-email-aisheng.dong@nxp.com> <1616484011-26702-4-git-send-email-aisheng.dong@nxp.com> From: Chanwoo Choi Message-ID: <3054611c-4f43-8432-bd14-1733ab82804b@gmail.com> Date: Wed, 24 Mar 2021 00:01:52 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <1616484011-26702-4-git-send-email-aisheng.dong@nxp.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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. > + > 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