linux-kernel - [PATCH 04/10] PM / devfreq: Add a recommended frequency helper

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Date:   Tue, 28 Sep 2021 23:42:48 -0500
From:   Samuel Holland <samuel@...lland.org>
To:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Rob Herring <robh+dt@...nel.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
        linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Samuel Holland <samuel@...lland.org>
Subject: [PATCH 04/10] PM / devfreq: Add a recommended frequency helper

This helper peforms the same function as devfreq_recommended_opp().
However, it works on devices without OPPs by iterating over freq_table.
Since freq_table is assumed to be sorted in ascending order, the
algorithm is relatively simple.

Devices with OPPs should continue using devfreq_recommended_opp(), as
that function respects disabled OPPs.

Signed-off-by: Samuel Holland <samuel@...lland.org>
---
 drivers/devfreq/devfreq.c | 27 +++++++++++++++++++++++++++
 include/linux/devfreq.h   |  2 ++
 2 files changed, 29 insertions(+)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index f5d27f5285db..fd46792297ad 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -1984,6 +1984,33 @@ subsys_initcall(devfreq_init);
  * OPP framework.
  */
 
+/**
+ * devfreq_recommended_freq() - Helper function to get the proper frequency from
+ *			        freq_table for the value given to target callback.
+ * @devfreq:	The devfreq device.
+ * @freq:	The frequency given to target function.
+ * @flags:	Flags handed from devfreq framework.
+ */
+void devfreq_recommended_freq(struct devfreq *devfreq,
+			      unsigned long *freq, u32 flags)
+{
+	const unsigned long *min = devfreq->profile->freq_table;
+	const unsigned long *max = min + devfreq->profile->max_state - 1;
+	const unsigned long *f;
+
+	if (flags & DEVFREQ_FLAG_LEAST_UPPER_BOUND) {
+		/* Find the first item lower than freq, or else min. */
+		for (f = max; f > min && *f > *freq; --f)
+			;
+	} else {
+		/* Find the first item higher than freq, or else max. */
+		for (f = min; f < max && *f < *freq; ++f)
+			;
+	}
+	*freq = *f;
+}
+EXPORT_SYMBOL(devfreq_recommended_freq);
+
 /**
  * devfreq_recommended_opp() - Helper function to get proper OPP for the
  *			     freq value given to target callback.
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index 142474b4af96..4d324fea8a78 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -239,6 +239,8 @@ void devfreq_resume(void);
 int update_devfreq(struct devfreq *devfreq);
 
 /* Helper functions for devfreq user device driver with OPP. */
+void devfreq_recommended_freq(struct devfreq *devfreq,
+			      unsigned long *freq, u32 flags);
 struct dev_pm_opp *devfreq_recommended_opp(struct device *dev,
 				unsigned long *freq, u32 flags);
 int devfreq_register_opp_notifier(struct device *dev,
-- 
2.31.1