linux-kernel - [PATCH V2 4/6] PM / devfreq: bail out early if no freq changes in devfreq_set

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Date:   Tue, 23 Mar 2021 10:59:17 +0800
From:   Dong Aisheng <aisheng.dong@....com>
To:     linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     dongas86@...il.com, kernel@...gutronix.de, shawnguo@...nel.org,
        linux-imx@....com, linux-kernel@...r.kernel.org,
        myungjoo.ham@...sung.com, kyungmin.park@...sung.com,
        cw00.choi@...sung.com, abel.vesa@....com,
        Dong Aisheng <aisheng.dong@....com>
Subject: [PATCH V2 4/6] PM / devfreq: bail out early if no freq changes in devfreq_set_target

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

Signed-off-by: Dong Aisheng <aisheng.dong@....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 b537fd9602cd..cacda7d1f858 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -403,13 +403,16 @@ 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);
@@ -426,7 +429,7 @@ 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);
 
 	devfreq_update_transitions(devfreq, cur_freq, new_freq,
@@ -445,7 +448,7 @@ 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;
 }
 
 /**
-- 
2.25.1