linux-kernel - [PATCH v4 2/2] hwmon: (pwm-fan): Make default PWM duty cycle configurable

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Message-Id: <20250103101448.890946-2-peter@korsgaard.com>
Date: Fri,  3 Jan 2025 11:14:48 +0100
From: Peter Korsgaard <peter@...sgaard.com>
To: Guenter Roeck <linux@...ck-us.net>,
	devicetree@...r.kernel.org,
	linux-hwmon@...r.kernel.org
Cc: Peter Korsgaard <peter@...sgaard.com>,
	Jean Delvare <jdelvare@...e.com>,
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v4 2/2] hwmon: (pwm-fan): Make default PWM duty cycle configurable

The pwm-fan driver uses full PWM (255) duty cycle at startup, which may not
always be desirable because of noise or power consumption peaks, so support
an optional "default-pwm" property (0..255) that can be used to specify the
default PWM duty cycle.

Signed-off-by: Peter Korsgaard <peter@...sgaard.com>
---
Changes since v3:
- Readded validation code from v2, reworded commit message

Changes since v2:
- Recreated/resent

Changes since v1:
- Rename property to default-pwm
- Drop u32 cast

 drivers/hwmon/pwm-fan.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index 53a1a968d00d..f49b5c2c64a9 100644
--- a/drivers/hwmon/pwm-fan.c
+++ b/drivers/hwmon/pwm-fan.c
@@ -499,6 +499,7 @@ static int pwm_fan_probe(struct platform_device *pdev)
 	const struct hwmon_channel_info **channels;
 	u32 pwm_min_from_stopped = 0;
 	u32 *fan_channel_config;
+	u32 default_pwm = MAX_PWM;
 	int channel_count = 1;	/* We always have a PWM channel. */
 	int i;
 
@@ -545,11 +546,17 @@ static int pwm_fan_probe(struct platform_device *pdev)
 
 	ctx->enable_mode = pwm_disable_reg_enable;
 
+	device_property_read_u32(dev, "default-pwm", &default_pwm);
+	if (default_pwm > MAX_PWM) {
+		dev_err(dev, "Invalid default-pwm: %u > %d\n", default_pwm, MAX_PWM);
+		return -EINVAL;
+	}
+
 	/*
-	 * Set duty cycle to maximum allowed and enable PWM output as well as
+	 * Set duty cycle to default and enable PWM output as well as
 	 * the regulator. In case of error nothing is changed
 	 */
-	ret = set_pwm(ctx, MAX_PWM);
+	ret = set_pwm(ctx, default_pwm);
 	if (ret) {
 		dev_err(dev, "Failed to configure PWM: %d\n", ret);
 		return ret;
-- 
2.39.5