linux-kernel - Re: [PATCH v3 3/4] arm64: dts: apple: t8103: Add i2c nodes

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Message-ID: <CACRpkdZghfRvox4aY4ROXYwFqiV6mnXZgw+42ZWYisXXgQ5+jQ@mail.gmail.com>
Date:   Wed, 24 Nov 2021 00:26:56 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Hector Martin <marcan@...can.st>
Cc:     Janne Grunau <j@...nau.net>, Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/4] arm64: dts: apple: t8103: Add i2c nodes

On Tue, Nov 23, 2021 at 3:43 PM Hector Martin <marcan@...can.st> wrote:

> For those following along in the list: the reason why i2c3 was getting
> stuck is because it seems the unused bus is weakly pulled low on these
> machines, which jams it.

That looks like some power saving attempt.

I suppose that means that even i2c buses that are in use
could be weakly pulled low when suspending the system
and maybe even inbetween transactions to save some
leak current.

Yours,
Linus Walleij