linux-kernel - [PATCH 04/11] PM / devfreq: bail out early if no freq changes in devfreq_set

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Date:   Tue,  9 Mar 2021 20:58:46 +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 04/11] 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 | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index bf3047896e41..6e80bf70e7b3 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -358,6 +358,9 @@ static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_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);
@@ -374,7 +377,7 @@ 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;
-- 
2.25.1