[PATCH v2 3/3] dt-bindings: hwmon: max31790: Add maxim,pwmout-pin-as-tach-input property
Chanh Nguyen
chanh at amperemail.onmicrosoft.com
Sat Jun 8 02:46:52 AEST 2024
On 09/05/2024 15:29, Krzysztof Kozlowski wrote:
> On 08/05/2024 05:44, Chanh Nguyen wrote:
>>>>>>
>>>>>
>>>>> I am not even sure how to define tach-ch to mean "use the pwm output pin
>>>>> associated with this tachometer input channel not as pwm output
>>>>> but as tachometer input". That would be a boolean, not a number.
>>>>>
>>>>
>>>> Thank Guenter,
>>>>
>>>> I reviewed again the "tach-ch" property, which is used in the
>>>> https://elixir.bootlin.com/linux/v6.9-rc6/source/Documentation/devicetree/bindings/hwmon/aspeed,g6-pwm-tach.yaml#L68 and https://elixir.bootlin.com/linux/v6.9-rc6/source/drivers/hwmon/aspeed-g6-pwm-tach.c#L434
>>>>
>>>> That is something completely different from my purpose.
>>>>
>>>
>>> Based on its definition, tach-ch is associated with fans, and it looks
>>> like the .yaml file groups multiple sets of fans into a single
>>> fan node.
>>>
>>> In the simple case that would be
>>> tach-ch = <1>
>>> ...
>>> tach-ch = <12>
>>>
>>> or, if all fans are controlled by a single pwm
>>> tach-ch = <1 2 3 4 5 6 8 9 10 11 12>
>>>
>>> The existence of tachometer channel 7..12 implies that pwm channel
>>> (tachometer
>>> channel - 6) is used as tachometer channel. That should be sufficient to
>>> program
>>> the chip for that channel. All you'd have to do is to ensure that pwm
>>> channel
>>> "X" is not listed as tachometer channel "X + 6", and program pwm channel
>>> "X - 6"
>>> for tachometer channels 7..12 as tachometer channels.
>>>
>>
>> Hi Guenter,
>>
>> I applied the patch [2/3] in my patch series
>> (https://lore.kernel.org/lkml/20240414042246.8681-3-chanh@os.amperecomputing.com/)
>>
>> My device tree is configured as below, I would like to configure PWMOUT
>> pins 5 and 6 to become the tachometer input pins.
>>
>
> And what is wrong in described common tach-ch property? I think we
> explained it three times and you did not provide any arguments, what's
> missing. Instead you say "I want something like this in DTS" which is
> not an argument and does not help discussion.
>
Hi Krzysztof,
Apologies for any inconvenience caused by the delayed response.
I'll to support the child nodes by having different tach-ch values. I
suggest the child nodes and the "tach-ch" is optional, it will not be
added to "required:". Do you have any comments? Please help me share!
This is a brief binding
...
properties:
compatible:
const: maxim,max31790
reg:
maxItems: 1
clocks:
maxItems: 1
resets:
maxItems: 1
patternProperties:
"^fan-[0-9]+$":
$ref: fan-common.yaml#
unevaluatedProperties: false
required:
- compatible
- reg
additionalProperties: false
examples:
- |
i2c {
#address-cells = <1>;
#size-cells = <0>;
pwm_provider: fan-controller at 20 {
compatible = "maxim,max31790";
reg = <0x20>;
clocks = <&sys_clk>;
resets = <&reset 0>;
fan-0 {
pwms = <&pwm_provider 1>;
tach-ch = <1 2>;
};
fan-1 {
pwms = <&pwm_provider 2>;
tach-ch = <7 8>;
};
};
};
If it's OK, I'm going to push the patch series v3 soon.
Thanks,
Chanh Ng
> Best regards,
> Krzysztof
>
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