linux-kernel - Re: [PATCH v3 3/4] hwmon: (adt7475) temperature smoothing

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Date:   Sun, 14 May 2017 14:55:25 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Chris Packham <Chris.Packham@...iedtelesis.co.nz>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>
Cc:     Tobi Wulff <Tobi.Wulff@...iedtelesis.co.nz>,
        Jean Delvare <jdelvare@...e.com>,
        Jonathan Corbet <corbet@....net>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/4] hwmon: (adt7475) temperature smoothing

On 05/14/2017 02:23 PM, Chris Packham wrote:
> On 15/05/17 03:40, Guenter Roeck wrote:
>> On 05/10/2017 08:45 PM, Chris Packham wrote:
>>> When enabled temperature smoothing allows ramping the fan speed over a
>>> configurable period of time instead of jumping to the new speed
>>> instantaneously.
>>>
>>> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
>>> ---
>>>
>>> Changes in v2:
>>> - use a single tempN_smoothing attribute
>>
>> This is a bit confusing. tempN suggests that the attribute would be associated
>> with a given temperature, not with fan control. Not that I have a better idea
>> for an attribute name, though, so unless you find a better name I am ok with it.
>>
>
> The datasheet is a bit confusing in this respect.
>
>  From the description of register 0x62:
>
> "Assuming that PWMx is associated with the Remote 1 temperature channel,
> these bits define the maximum rate of change of the PWMx output for
> Remote 1 temperature related changes. Instead of the fan speed jumping
> instantaneously to its newly determined speed, it ramps
> gracefully at the rate determined by these bits. This feature ultimately
> enhances the acoustics of the fan."
>
> Based on my reading it's a property of the temperature input not of the
> PWM. If you changed pwmN_auto_channels_temp this setting would stay with
> the temperature sensor not the PWM.
>

Agreed, that is why I said that I don't have a better idea ...

Guenter