From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
To: Guenter Roeck <linux@roeck-us.net>,
Chanh Nguyen <chanh@amperemail.onmicrosoft.com>,
Conor Dooley <conor@kernel.org>
Cc: Chanh Nguyen <chanh@os.amperecomputing.com>,
Jean Delvare <jdelvare@suse.com>,
Rob Herring <robh+dt@kernel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
Conor Dooley <conor+dt@kernel.org>,
Justin Ledford <justinledford@google.com>,
devicetree@vger.kernel.org, linux-hwmon@vger.kernel.org,
linux-kernel@vger.kernel.org,
OpenBMC Maillist <openbmc@lists.ozlabs.org>,
Open Source Submission <patches@amperecomputing.com>,
Phong Vo <phong@os.amperecomputing.com>,
Thang Nguyen <thang@os.amperecomputing.com>,
Quan Nguyen <quan@os.amperecomputing.com>
Subject: Re: [PATCH v2 3/3] dt-bindings: hwmon: max31790: Add maxim,pwmout-pin-as-tach-input property
Date: Thu, 25 Apr 2024 17:46:02 +0200 [thread overview]
Message-ID: <b79b5323-196f-41bc-b47a-d350c49d769a@linaro.org> (raw)
In-Reply-To: <396b47f5-9604-44ab-881f-94d0664bcab8@roeck-us.net>
On 25/04/2024 16:05, Guenter Roeck wrote:
> On 4/25/24 03:33, Chanh Nguyen wrote:
>>
>>
>> On 24/04/2024 00:02, Conor Dooley wrote:
>>> [EXTERNAL EMAIL NOTICE: This email originated from an external sender. Please be mindful of safe email handling and proprietary information protection practices.]
>>>
>>
>
> The quote doesn't make much sense.
>
>> Sorry Conor, there may be confusion here. I mean the mapping of the PWM output to the TACH input, which is on the MAX31790, and it is not sure a common feature on all fan controllers.
>>
>
> I think the term "mapping" is a bit confusing here.
>
> tach-ch, as I understand it, is supposed to associate a tachometer input
> with a pwm output, meaning the fan speed measured with the tachometer input
> is expected to change if the pwm output changes.
>
> On MAX31790, it is possible to configure a pwm output pin as tachometer input pin.
> That is something completely different. Also, the association is fixed.
> If the first pwm channel is used as tachometer channel, it would show up as 7th
> tachometer channel. If the 6th pwm channel is configured to be used as tachometer
> input, it would show up as 12th tachometer channel.
>
> Overall, the total number of channels on MAX31790 is always 12. 6 of them
> are always tachometer inputs, the others can be configured to either be a
> pwm output or a tachometer input.
>
> pwm outputs on MAX31790 are always tied to the matching tachometer inputs
> (pwm1 <--> tach1 etc) and can not be reconfigured, meaning tach-ch for
> channel X would always be X.
>
>> I would like to open a discussion about whether we should use the tach-ch property on the fan-common.yaml
>>
>> I'm looking forward to hearing comments from everyone. For me, both tach-ch and vendor property are good.
>>
>
> 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.
Thanks for explanation. So this is basically pin controller function
choice - kind of output or input, although not in terms of GPIO.
Shouldn't we have then fan children which will be consumers of PWMs?
Having a consumer makes pin PWM output. Then tach-ch says which pins are
tachometer for given fan? Just like aspeed,g6-pwm-tach.yaml has?
Best regards,
Krzysztof
next prev parent reply other threads:[~2024-04-25 15:46 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-14 4:22 [PATCH v2 0/3] Update the max31790 driver Chanh Nguyen
2024-04-14 4:22 ` [PATCH v2 1/3] dt-bindings: hwmon: Add maxim max31790 bindings Chanh Nguyen
2024-04-14 6:03 ` Krzysztof Kozlowski
2024-04-16 4:38 ` Chanh Nguyen
2024-04-14 4:22 ` [PATCH v2 2/3] hwmon: (max31790): Support config PWM output becomes TACH Chanh Nguyen
2024-04-14 8:03 ` Christophe JAILLET
2024-04-16 5:27 ` Chanh Nguyen
2024-04-16 17:39 ` Christophe JAILLET
2024-04-17 2:54 ` Chanh Nguyen
2024-04-14 4:22 ` [PATCH v2 3/3] dt-bindings: hwmon: max31790: Add maxim,pwmout-pin-as-tach-input property Chanh Nguyen
2024-04-14 6:07 ` Krzysztof Kozlowski
2024-04-16 4:52 ` Chanh Nguyen
2024-04-23 8:45 ` Chanh Nguyen
2024-04-23 17:02 ` Conor Dooley
2024-04-25 10:33 ` Chanh Nguyen
2024-04-25 14:05 ` Guenter Roeck
2024-04-25 15:46 ` Krzysztof Kozlowski [this message]
2024-04-25 15:56 ` Conor Dooley
2024-05-05 10:08 ` Chanh Nguyen
2024-05-05 15:40 ` Guenter Roeck
2024-05-08 3:44 ` Chanh Nguyen
2024-05-08 16:47 ` Conor Dooley
2024-06-07 16:47 ` Chanh Nguyen
2024-06-07 23:14 ` Guenter Roeck
2024-06-08 8:32 ` Chanh Nguyen
2024-05-09 8:29 ` Krzysztof Kozlowski
2024-06-07 16:46 ` Chanh Nguyen
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