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From: Vadim Pasternak <vadimp@nvidia.com>
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CC: <jdelvare@suse.com>, <linux-hwmon@vger.kernel.org>, <idosch@nvidia.com>,
	<razor@blackwall.org>, Vadim Pasternak <vadimp@nvidia.com>
Subject: [PATCH hwmon 1/1] hwmon: mlxreg-fan: Prevent fans from getting stuck at 0 RPM
Date: Wed, 30 Jul 2025 23:17:15 +0300
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The fans controlled by the driver can get stuck at 0 RPM if they are
configured below a 20% duty cycle. The driver tries to avoid this by
enforcing a minimum duty cycle of 20%, but this is done after the fans
are registered with the thermal subsystem. This is too late as the
thermal subsystem can set their current state before the driver is able
to enforce the minimum duty cycle.

Fix by setting the minimum duty cycle before registering the fans with
the thermal subsystem.

Fixes: d7efb2ebc7b3 ("hwmon: (mlxreg-fan) Extend driver to support multiply cooling devices")
Reported-by: Nikolay Aleksandrov <razor@blackwall.org>
Tested-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
---
 drivers/hwmon/mlxreg-fan.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/mlxreg-fan.c b/drivers/hwmon/mlxreg-fan.c
index 01faf1a8f55a..137a90dd2075 100644
--- a/drivers/hwmon/mlxreg-fan.c
+++ b/drivers/hwmon/mlxreg-fan.c
@@ -581,15 +581,14 @@ static int mlxreg_fan_cooling_config(struct device *dev, struct mlxreg_fan *fan)
 		if (!pwm->connected)
 			continue;
 		pwm->fan = fan;
+		/* Set minimal PWM speed. */
+		pwm->last_hwmon_state = MLXREG_FAN_PWM_DUTY2STATE(MLXREG_FAN_MIN_DUTY);
 		pwm->cdev = devm_thermal_of_cooling_device_register(dev, NULL, mlxreg_fan_name[i],
 								    pwm, &mlxreg_fan_cooling_ops);
 		if (IS_ERR(pwm->cdev)) {
 			dev_err(dev, "Failed to register cooling device\n");
 			return PTR_ERR(pwm->cdev);
 		}
-
-		/* Set minimal PWM speed. */
-		pwm->last_hwmon_state = MLXREG_FAN_PWM_DUTY2STATE(MLXREG_FAN_MIN_DUTY);
 	}
 
 	return 0;
-- 
2.34.1