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

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Message-ID: <CACRpkdZ4==HvMYrJe2jQMzeYqh65OKLEo9WEWDGZAZ8u7jkxFw@mail.gmail.com>
Date:   Thu, 25 Nov 2021 16:50:28 +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 Wed, Nov 24, 2021 at 6:42 AM Hector Martin <marcan@...can.st> wrote:

> Pulling down an I2C bus between transactions is not legal; the idle
> state has to be high.

Oh right.

> Apple are actually not very good at configuring GPIOs for power saving;
> e.g. the I/Os for that unused i2c bus still have their input buffers
> turned on, which is a waste of power. If they wanted to save the
> smallest drop of power they'd turn that off. But the effect of this is
> so trivial it probably makes no difference in the context of a laptop,
> nevermind a desktop like the Mac Mini.

Hm that's true. The saying is that 99% is the backlight, the remaining 1% isn't
so significant after that.

Yours,
Linus Walleij