linux-kernel - [PATCH] PM / devfreq: Init user limits from OPP limits, not viceversa

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Date:   Wed, 16 May 2018 15:57:09 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Brian Norris <briannorris@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: [PATCH] PM / devfreq: Init user limits from OPP limits, not viceversa

Commit ab8f58ad72c4 ("PM / devfreq: Set min/max_freq when adding
the devfreq device") introduced the initialization of the user
limits min/max_freq from the lowest/highest available OPPs. Later
commit f1d981eaecf8 ("PM / devfreq: Use the available min/max
frequency") added scaling_min/max_freq, which actually represent
the frequencies of the lowest/highest available OPP. scaling_min/
max_freq are initialized with the values from min/max_freq, which
is totally correct in the context, but a bit awkward to read.

Swap the initialization and assign scaling_min/max_freq with the
OPP freqs and then the user limts min/max_freq with scaling_min/
max_freq.

Needless to say that this change is a NOP, intended to improve
readability.

Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
---
Additional context: I'm considering to introduce the concept of
a devfreq policy, which would probably move min/max_freq inside
of a struct policy, this would make the initialization even
more awkward to read. If this moves forward I might also propose
to rename scaling_min/max_freq to something like min/max_opp_freq
to avoid confusion with the frequencies in the policy (cpufreq uses
scaling_min/max_freq for the sysfs attributes of the policy
limits).

 drivers/devfreq/devfreq.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index fe2af6aa88fc..0057ef5b0a98 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -604,21 +604,21 @@ struct devfreq *devfreq_add_device(struct device *dev,
 		mutex_lock(&devfreq->lock);
 	}
 
-	devfreq->min_freq = find_available_min_freq(devfreq);
-	if (!devfreq->min_freq) {
+	devfreq->scaling_min_freq = find_available_min_freq(devfreq);
+	if (!devfreq->scaling_min_freq) {
 		mutex_unlock(&devfreq->lock);
 		err = -EINVAL;
 		goto err_dev;
 	}
-	devfreq->scaling_min_freq = devfreq->min_freq;
+	devfreq->min_freq = devfreq->scaling_min_freq;
 
-	devfreq->max_freq = find_available_max_freq(devfreq);
-	if (!devfreq->max_freq) {
+	devfreq->scaling_max_freq = find_available_max_freq(devfreq);
+	if (!devfreq->scaling_max_freq) {
 		mutex_unlock(&devfreq->lock);
 		err = -EINVAL;
 		goto err_dev;
 	}
-	devfreq->scaling_max_freq = devfreq->max_freq;
+	devfreq->max_freq = devfreq->scaling_max_freq;
 
 	dev_set_name(&devfreq->dev, "devfreq%d",
 				atomic_inc_return(&devfreq_no));
-- 
2.17.0.441.gb46fe60e1d-goog