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Message-ID: <e590e3ba-f446-4f20-9618-d4ff388586ad@roeck-us.net>
Date: Mon, 4 Mar 2024 16:41:17 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Zev Weiss <zev@...ilderbeest.net>, baneric926@...il.com
Cc: jdelvare@...e.com, robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
conor+dt@...nel.org, corbet@....net, linux-hwmon@...r.kernel.org,
devicetree@...r.kernel.org, kcfeng0@...oton.com, kwliu@...oton.com,
openbmc@...ts.ozlabs.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, DELPHINE_CHIU@...ynn.com,
naresh.solanki@...ements.com, billy_tsai@...eedtech.com,
Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v4 1/3] dt-bindings: hwmon: fan: Add fan binding to schema
On 3/4/24 16:22, Zev Weiss wrote:
> On Mon, Feb 26, 2024 at 04:56:04PM PST, baneric926@...il.com wrote:
>> From: Naresh Solanki <naresh.solanki@...ements.com>
>>
>> Add common fan properties bindings to a schema.
>>
>> Bindings for fan controllers can reference the common schema for the
>> fan
>>
>> child nodes:
>>
>> patternProperties:
>> "^fan@[0-2]":
>> type: object
>> $ref: fan-common.yaml#
>> unevaluatedProperties: false
>>
>> Reviewed-by: Rob Herring <robh@...nel.org>
>> Signed-off-by: Naresh Solanki <naresh.solanki@...ements.com>
>> Signed-off-by: Billy Tsai <billy_tsai@...eedtech.com>
>> Signed-off-by: Ban Feng <kcfeng0@...oton.com>
>> ---
>> .../devicetree/bindings/hwmon/fan-common.yaml | 78 +++++++++++++++++++
>> 1 file changed, 78 insertions(+)
>> create mode 100644 Documentation/devicetree/bindings/hwmon/fan-common.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/hwmon/fan-common.yaml b/Documentation/devicetree/bindings/hwmon/fan-common.yaml
>> new file mode 100644
>> index 000000000000..15c591c74545
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/hwmon/fan-common.yaml
>> @@ -0,0 +1,78 @@
>> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/hwmon/fan-common.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Common Fan Properties
>> +
>> +maintainers:
>> + - Naresh Solanki <naresh.solanki@...ements.com>
>> + - Billy Tsai <billy_tsai@...eedtech.com>
>> +
>> +properties:
>> + max-rpm:
>> + description:
>> + Max RPM supported by fan.
>> + $ref: /schemas/types.yaml#/definitions/uint32
>> + maximum: 100000
>> +
>> + 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.
Guenter
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