Re: [PATCH v4 1/3] dt-bindings: hwmon: fan: Add fan binding to schema

From: Guenter Roeck
Date: Mon Mar 04 2024 - 19:49:46 EST


On 3/4/24 16:41, Guenter Roeck wrote:

+
+  min-rpm:
+    description:
+      Min RPM supported by fan.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    maximum: 1000

I can't say with certainty that it's not, but are we sure 1000 is low enough?  Looking at just what I've got on hand, an 80mm fan I have will run steadily at about 1500RPM, and I'd assume larger ones (e.g. 120mm) could potentially go significantly lower...


I have seen fans which run stable at < 400rpm.
One of my systems right now has:

fan1:              732 RPM  (min =    0 RPM)
fan2:                0 RPM  (min =    0 RPM)
fan3:              586 RPM  (min =    0 RPM)
fan4:              472 RPM  (min =    0 RPM)
fan5:              480 RPM  (min =    0 RPM)

Those are 80mm fans. A quick check shows that various Noctua fans have a
minimum speed of 300 rpm. So 1000 is indeed a bit high for the minimum speed.


No, wait, that is the _maximum_ minimum speed. Got me there.

So, there is Noctua's NF-A4x20 PWM with a minimum rotational speed of 1,200 RPM.

If I interpret
https://www.mouser.com/datasheet/2/471/SanyoDenki_San_Ace_40LG28_E-3198440.pdf
correctly, it lists some fans with a minimum speed of 7,500 RPM.

Guenter