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

Peter Korsgaard
2025-01-03T10:15:03Z

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@korsgaard.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