linux-kernel - Re: [PATCH v3 2/2] i2c: mv64xxx: add an optional reset-gpios property

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Message-ID: <61593e5f-5d54-4e33-8926-ef68e7fba49e@alliedtelesis.co.nz>
Date:   Tue, 24 Oct 2023 20:54:05 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     Andi Shyti <andi.shyti@...nel.org>
CC:     "gregory.clement@...tlin.com" <gregory.clement@...tlin.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/2] i2c: mv64xxx: add an optional reset-gpios property


On 25/10/23 09:37, Andi Shyti wrote:
> Hi Chris,
>
>>> as you are working on the v4...
>>>
>>> ...
>>>
>>>> +	if (drv_data->reset_gpio) {
>>>> +		usleep_range(reset_duration, reset_duration + 10);
>>> I'm not against this, but it's not optimal unless we know more or
>>> less what to expect from reset_duration.
>>>
>>> Do we have a rough idea of what reset_duration is? If we don't
>>> then you could consider using a generic "fsleep(reset_duration);"
>>> Would it work?
>> flseep() would work for me. All of the devices I'm testing with seem to
>> be fine with a very short reset pulse, they'd probably be fine with no
>> delay at all.
> you know this better than me :-)
> If you say that a delay is not necessary, then I'm also fine.
>
> In any case, we are in probe and I don't think it's time
> critical, so that a little delay wouldn't hurt and make everyone
> happy.
>
> Either way I'm fine as long as you use the correct sleeping
> function.

My particular hardware doesn't need it but for this to be generally 
usable I think it is necessary to provide the capability for some kind 
of hardware specific reset-duration. I'll look at fsleep() for v4 (or 
say why I've stuck with usleep_range() in the changelog).

> Andi