linux-kernel - [PATCH 1/2] regulator: core: Sleep (not delay) in set

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Message-Id: <20220418141158.1.If0fc61a894f537b052ca41572aff098cf8e7e673@changeid>
Date:   Mon, 18 Apr 2022 14:12:39 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>
Cc:     Matthias Kaehlcke <mka@...omium.org>, linux-kernel@...r.kernel.org,
        Brian Norris <briannorris@...omium.org>
Subject: [PATCH 1/2] regulator: core: Sleep (not delay) in set_voltage()

These delays can be relatively large (e.g., hundreds of microseconds on
RK3399 Gru systems). Per Documentation/timers/timers-howto.rst, that
should usually use a sleeping delay. Let's use fsleep() to handle both
large and small delays appropriately. This avoids burning a bunch of CPU
time and hurting scheduling latencies when hitting regulators a lot
(e.g., during cpufreq).

The sleep vs. delay issue choice has been made differently over time --
early versions of RK3399 Gru PWM-regulator support used usleep_range()
in pwm-regulator.c. More of this got moved into the regulator core,
in commits like:

73e705bf81ce regulator: core: Add set_voltage_time op

At the same time, the sleep turned into a delay.

It's OK to sleep here, as we aren't in an atomic contexts. (All our
callers grab various mutexes already.)

Signed-off-by: Brian Norris <briannorris@...omium.org>
---

 drivers/regulator/core.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index d2553970a67b..223c6d71a2b2 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -3548,12 +3548,7 @@ static int _regulator_do_set_voltage(struct regulator_dev *rdev,
 	}

 	/* Insert any necessary delays */
-	if (delay >= 1000) {
-		mdelay(delay / 1000);
-		udelay(delay % 1000);
-	} else if (delay) {
-		udelay(delay);
-	}
+	fsleep(delay);

 	if (best_val >= 0) {
 		unsigned long data = best_val;
-- 
2.36.0.rc0.470.gd361397f0d-goog