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

Arnd Bergmann
2021-09-27T07:42:38Z

On Sun, Sep 26, 2021 at 12:00 PM Sven Peter <sven@svenpeter.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@arndb.de>