linux-kernel - Re: [PATCH 00/10] Add Apple M1 support to PASemi i2c driver

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Message-ID: <CAK8P3a3Lt2QXk+aWLtXUXjjNhKJwNns6d9r=Yh5_aWETuvZTpQ@mail.gmail.com>
Date:   Mon, 27 Sep 2021 09:42:18 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Sven Peter <sven@...npeter.dev>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Olof Johansson <olof@...om.net>, Arnd Bergmann <arnd@...db.de>,
        Hector Martin <marcan@...can.st>,
        Mohamed Mediouni <mohamed.mediouni@...amail.com>,
        Stan Skowronek <stan@...ellium.com>,
        Mark Kettenis <mark.kettenis@...all.nl>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Linux I2C <linux-i2c@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 00/10] Add Apple M1 support to PASemi i2c driver

On Sun, Sep 26, 2021 at 12:00 PM Sven Peter <sven@...npeter.dev> wrote:
>
> This series adds support for the I2C controller found on Apple Silicon Macs
> which has quite a bit of history:
>
> Apple bought P.A. Semi in 2008 and it looks like a part of its legacy continues
> to live on in the M1. This controller has actually been used since at least the
> iPhone 4S and hasn't changed much since then.
> Essentially, there are only a few differences that matter:
>
>         - The controller no longer is a PCI device
>         - Starting at some iPhone an additional bit in one register
>           must be set in order to start transmissions.
>         - The reference clock and hence the clock dividers are different
>
> In order to add support for a platform device I first replaced PCI-specific
> bits and split out the PCI driver to its own file. Then I added support
> to make the clock divider configurable and converted the driver to use
> managed device resources to make it a bit simpler.
>
> The Apple and PASemi driver will never be compiled in the same kernel
> since the Apple one will run on arm64 while the original PASemi driver
> will only be useful on powerpc.
> I've thus followed the octeon (mips)/thunderx(arm64) approach to do the
> split: I created a -core.c file which contains the shared logic and just
> compile that one for both the PASemi and the new Apple driver.

This looks all very good to me, I had one very minor comment.

Whole series

Reviewed-by: Arnd Bergmann <arnd@...db.de>