On the Dell Precision 3650 Tower, the EC ignores fan speed writes unless
automatic BIOS fan control is disabled first. The I8K_FAN_30A3_31A3 SMM
code pair works on this machine through the WMI-SMM backend: after
writing 1 to pwm1_enable, all three fans (CPU, front, top) accept the
three fan states and report matching RPM, and writing 2 hands control
back to the BIOS. I8K_FAN_34A3_35A3 was tested as well and also works;
I8K_FAN_30A3_31A3 is used since it matches recent OEM software.

Tested on BIOS 1.48.0 with kernels 7.0.0-30 and 7.0.0-31 (Ubuntu 26.04).

Signed-off-by: Patrick Pepin <patpep@me.com>
---
v2: use I8K_FAN_30A3_31A3 instead of I8K_FAN_34A3_35A3 as suggested by
    Armin Wolf (both pairs tested working on this machine). Pali's
    Acked-by from v1 is not carried over because of this change.

 drivers/hwmon/dell-smm-hwmon.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
index 7ed94a3db..99a58ed26 100644
--- a/drivers/hwmon/dell-smm-hwmon.c
+++ b/drivers/hwmon/dell-smm-hwmon.c
@@ -1639,6 +1639,14 @@ static const struct dmi_system_id i8k_whitelist_fan_control[] __initconst = {
 		},
 		.driver_data = (void *)&i8k_fan_control_data[I8K_FAN_34A3_35A3],
 	},
+	{
+		.ident = "Dell Precision 3650 Tower",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+			DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "Precision 3650 Tower"),
+		},
+		.driver_data = (void *)&i8k_fan_control_data[I8K_FAN_30A3_31A3],
+	},
 	{
 		.ident = "Dell Optiplex 7090",
 		.matches = {
-- 
2.53.0

On Mon, Sep 14, 2026 at 08:09:55AM +0000, Patrick Pepin wrote:
> On the Dell Precision 3650 Tower, the EC ignores fan speed writes unless
> automatic BIOS fan control is disabled first. The I8K_FAN_30A3_31A3 SMM
> code pair works on this machine through the WMI-SMM backend: after
> writing 1 to pwm1_enable, all three fans (CPU, front, top) accept the
> three fan states and report matching RPM, and writing 2 hands control
> back to the BIOS. I8K_FAN_34A3_35A3 was tested as well and also works;
> I8K_FAN_30A3_31A3 is used since it matches recent OEM software.
> 
> Tested on BIOS 1.48.0 with kernels 7.0.0-30 and 7.0.0-31 (Ubuntu 26.04).
> 
> Signed-off-by: Patrick Pepin <patpep@me.com>
> Acked-by: Pali Rohár <pali@kernel.org>

Applied.

Thanks,
Guenter

On Monday 14 September 2026 08:09:55 Patrick Pepin wrote:
> On the Dell Precision 3650 Tower, the EC ignores fan speed writes unless
> automatic BIOS fan control is disabled first. The I8K_FAN_30A3_31A3 SMM
> code pair works on this machine through the WMI-SMM backend: after
> writing 1 to pwm1_enable, all three fans (CPU, front, top) accept the
> three fan states and report matching RPM, and writing 2 hands control
> back to the BIOS. I8K_FAN_34A3_35A3 was tested as well and also works;
> I8K_FAN_30A3_31A3 is used since it matches recent OEM software.
> 
> Tested on BIOS 1.48.0 with kernels 7.0.0-30 and 7.0.0-31 (Ubuntu 26.04).
> 
> Signed-off-by: Patrick Pepin <patpep@me.com>

Acked-by: Pali Rohár <pali@kernel.org>

> ---
> v2: use I8K_FAN_30A3_31A3 instead of I8K_FAN_34A3_35A3 as suggested by
>     Armin Wolf (both pairs tested working on this machine). Pali's
>     Acked-by from v1 is not carried over because of this change.
> 
>  drivers/hwmon/dell-smm-hwmon.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
> index 7ed94a3db..99a58ed26 100644
> --- a/drivers/hwmon/dell-smm-hwmon.c
> +++ b/drivers/hwmon/dell-smm-hwmon.c
> @@ -1639,6 +1639,14 @@ static const struct dmi_system_id i8k_whitelist_fan_control[] __initconst = {
>  		},
>  		.driver_data = (void *)&i8k_fan_control_data[I8K_FAN_34A3_35A3],
>  	},
> +	{
> +		.ident = "Dell Precision 3650 Tower",
> +		.matches = {
> +			DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
> +			DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "Precision 3650 Tower"),
> +		},
> +		.driver_data = (void *)&i8k_fan_control_data[I8K_FAN_30A3_31A3],
> +	},
>  	{
>  		.ident = "Dell Optiplex 7090",
>  		.matches = {
> -- 
> 2.53.0
>