[RESEND PATCH 1/2] dt-bindings: hwmon: pwm-fan: Document after shutdown fan settings

[RESEND PATCH 1/2] dt-bindings: hwmon: pwm-fan: Document after shutdown fan settings

[Marek Vasut]

Document fan-shutdown-percent property, used to describe fan RPM in percent
set during shutdown. This is used to keep the fan running at fixed RPM after
the kernel shut down, which is useful on hardware that does keep heating
itself even after the kernel did shut down, for example from some sort of
management core.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
---
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Conor Dooley <conor+dt@kernel.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Jean Delvare <jdelvare@suse.com>
Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: devicetree@vger.kernel.org
Cc: linux-hwmon@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org
---
 Documentation/devicetree/bindings/hwmon/pwm-fan.yaml | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml b/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml
index 8b4ed5ee962fb..a84cc3a4cfdca 100644
--- a/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml
+++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.yaml
@@ -31,6 +31,15 @@ properties:
       it must be self resetting edge interrupts.
     maxItems: 1
 
+  fan-shutdown-percent:
+    description:
+      Fan RPM in percent set during shutdown. This is used to keep the fan
+      running at fixed RPM after the kernel shut down, which is useful on
+      hardware that does keep heating itself even after the kernel did shut
+      down, for example from some sort of management core.
+    minimum: 0
+    maximum: 100
+
   fan-stop-to-start-percent:
     description:
       Minimum fan RPM in percent to start when stopped.
-- 
2.50.1

[RESEND PATCH 2/2] hwmon: (pwm-fan) Implement after shutdown fan settings

[Marek Vasut]

Add fan-shutdown-percent property, used to describe fan RPM in percent set
during shutdown. This is used to keep the fan running at fixed RPM after
the kernel shut down, which is useful on hardware that does keep heating
itself even after the kernel did shut down, for example from some sort of
management core. The current behavior of pwm-fan is to unconditionally
stop the fan on shutdown, which is not always the safe and correct thing
to do, so let the hardware description include the expected behavior.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
---
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Conor Dooley <conor+dt@kernel.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Jean Delvare <jdelvare@suse.com>
Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: devicetree@vger.kernel.org
Cc: linux-hwmon@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org
---
 drivers/hwmon/pwm-fan.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index d0fe53451bdf8..37269db2de84f 100644
--- a/drivers/hwmon/pwm-fan.c
+++ b/drivers/hwmon/pwm-fan.c
@@ -64,6 +64,7 @@ struct pwm_fan_ctx {
 
 	u64 pwm_duty_cycle_from_stopped;
 	u32 pwm_usec_from_stopped;
+	u8 pwm_shutdown;
 };
 
 /* This handler assumes self resetting edge triggered interrupt. */
@@ -484,9 +485,14 @@ static void pwm_fan_cleanup(void *__ctx)
 	struct pwm_fan_ctx *ctx = __ctx;
 
 	timer_delete_sync(&ctx->rpm_timer);
-	/* Switch off everything */
-	ctx->enable_mode = pwm_disable_reg_disable;
-	pwm_fan_power_off(ctx, true);
+	if (ctx->pwm_shutdown) {
+		ctx->enable_mode = pwm_enable_reg_enable;
+		__set_pwm(ctx, ctx->pwm_shutdown);
+	} else {
+		/* Switch off everything */
+		ctx->enable_mode = pwm_disable_reg_disable;
+		pwm_fan_power_off(ctx, true);
+	}
 }
 
 static int pwm_fan_probe(struct platform_device *pdev)
@@ -498,6 +504,7 @@ static int pwm_fan_probe(struct platform_device *pdev)
 	int ret;
 	const struct hwmon_channel_info **channels;
 	u32 initial_pwm, pwm_min_from_stopped = 0;
+	u32 pwm_shutdown_percent = 0;
 	u32 *fan_channel_config;
 	int channel_count = 1;	/* We always have a PWM channel. */
 	int i;
@@ -648,6 +655,11 @@ static int pwm_fan_probe(struct platform_device *pdev)
 		channels[1] = &ctx->fan_channel;
 	}
 
+	ret = device_property_read_u32(dev, "fan-shutdown-percent",
+				       &pwm_shutdown_percent);
+	if (!ret && pwm_shutdown_percent)
+		ctx->pwm_shutdown = (clamp(pwm_shutdown_percent, 0, 100) * 255) / 100;
+
 	ret = device_property_read_u32(dev, "fan-stop-to-start-percent",
 				       &pwm_min_from_stopped);
 	if (!ret && pwm_min_from_stopped) {
-- 
2.50.1

Re: [RESEND PATCH 2/2] hwmon: (pwm-fan) Implement after shutdown fan settings

[Wolfram Sang]

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On Thu, Sep 04, 2025 at 10:21:10PM +0200, Marek Vasut wrote:
> Add fan-shutdown-percent property, used to describe fan RPM in percent set
> during shutdown. This is used to keep the fan running at fixed RPM after
> the kernel shut down, which is useful on hardware that does keep heating
> itself even after the kernel did shut down, for example from some sort of
> management core. The current behavior of pwm-fan is to unconditionally
> stop the fan on shutdown, which is not always the safe and correct thing
> to do, so let the hardware description include the expected behavior.
> 
> Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>

Works for me as promised!

Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>


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Re: [RESEND PATCH 1/2] dt-bindings: hwmon: pwm-fan: Document after shutdown fan settings

[Conor Dooley]

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On Thu, Sep 04, 2025 at 10:21:09PM +0200, Marek Vasut wrote:
> Document fan-shutdown-percent property, used to describe fan RPM in percent
> set during shutdown. This is used to keep the fan running at fixed RPM after
> the kernel shut down, which is useful on hardware that does keep heating
> itself even after the kernel did shut down, for example from some sort of
> management core.
> 
> Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>

Acked-by: Conor Dooley <conor.dooley@microchip.com>

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Re: [RESEND PATCH 1/2] dt-bindings: hwmon: pwm-fan: Document after shutdown fan settings

[Guenter Roeck]

On Thu, Sep 04, 2025 at 10:21:09PM +0200, Marek Vasut wrote:
> Document fan-shutdown-percent property, used to describe fan RPM in percent
> set during shutdown. This is used to keep the fan running at fixed RPM after
> the kernel shut down, which is useful on hardware that does keep heating
> itself even after the kernel did shut down, for example from some sort of
> management core.
> 
> Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
> Acked-by: Conor Dooley <conor.dooley@microchip.com>

Applied.

Guenter

Re: [RESEND PATCH 2/2] hwmon: (pwm-fan) Implement after shutdown fan settings

[Guenter Roeck]

On Thu, Sep 04, 2025 at 10:21:10PM +0200, Marek Vasut wrote:
> Add fan-shutdown-percent property, used to describe fan RPM in percent set
> during shutdown. This is used to keep the fan running at fixed RPM after
> the kernel shut down, which is useful on hardware that does keep heating
> itself even after the kernel did shut down, for example from some sort of
> management core. The current behavior of pwm-fan is to unconditionally
> stop the fan on shutdown, which is not always the safe and correct thing
> to do, so let the hardware description include the expected behavior.
> 
> Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
> Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

Applied.

Guenter