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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/31/25 09:16, Francesco Dolcini wrote: > Hello Guenter, > > > On Mon, Mar 31, 2025 at 09:01:08AM -0700, Guenter Roeck wrote: >> On 3/31/25 08:52, Francesco Dolcini wrote: >>> From: Francesco Dolcini >>> >>> Add properties to describe the fan and the PWM controller output. >>> >>> Link: https://www.ti.com/lit/gpn/amc6821 >>> Signed-off-by: Francesco Dolcini >>> --- >>> v3: >>> - explicitly describe the fan, use standard PWM and FAN bindings >>> - pwm.yaml cannot be referenced, because of the $nodename pattern that is >>> enforced there >>> v2: https://lore.kernel.org/all/20250224180801.128685-2-francesco@dolcini.it/ >>> - no changes >>> v1: https://lore.kernel.org/all/20250218165633.106867-2-francesco@dolcini.it/ >>> --- >>> .../devicetree/bindings/hwmon/ti,amc6821.yaml | 14 +++++++++++++- >>> 1 file changed, 13 insertions(+), 1 deletion(-) >>> >>> diff --git a/Documentation/devicetree/bindings/hwmon/ti,amc6821.yaml b/Documentation/devicetree/bindings/hwmon/ti,amc6821.yaml >>> index 5d33f1a23d03..94aca9c378e6 100644 >>> --- a/Documentation/devicetree/bindings/hwmon/ti,amc6821.yaml >>> +++ b/Documentation/devicetree/bindings/hwmon/ti,amc6821.yaml >>> @@ -28,6 +28,13 @@ properties: >>> i2c-mux: >>> type: object >>> + fan: >>> + $ref: fan-common.yaml# >>> + unevaluatedProperties: false >>> + >>> + "#pwm-cells": >>> + const: 3 >>> + >>> required: >>> - compatible >>> - reg >>> @@ -50,9 +57,14 @@ examples: >>> #address-cells = <1>; >>> #size-cells = <0>; >>> - fan@18 { >>> + fan_controller: fan@18 { >>> compatible = "ti,amc6821"; >>> reg = <0x18>; >>> + #pwm-cells = <3>; >>> + >>> + fan { >>> + pwms = <&fan_controller 0 40000 0>; >> >> There is no explanation for the parameters. I guess that the first is the index and the >> second is the frequency. The index is not used and can be dropped (there is just a single >> channel), and the frequency only makes sense if it can actually be configured. > > The PWM period can be configured, the HW supports it, so I think is a > good idea to properly describe the HW now that I am modifying the > binding and not have the situation in which we need it in 1 month. > > The instance is just one, it's correct, but there is an assumption > pretty much everywhere that these 3 #cells are > - PWM instance > - PWM period in ns > - PWM flags > > I decided to keep the first cell there, with the PWM instance, for this > reason, even as you correctly wrote it would not be required here. > > With that said, looking at existing binding, the description is almost > never present. > That is not a valid argument. > I would proceed this way for v4: > - keep the first cell as PWM instance > - add the description > We just had another driver where we dropped the pwm instance number because it is unnecessary. See commit a25633a00906. I very much prefer to keep it that way if it is not needed. Everything else is just confusing. It is bad enough that the sub-node is needed. We should not make it worse. Thanks, Guenter