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

Sven Peter sven at svenpeter.dev
Sun Sep 26 19:58:37 AEST 2021


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.

Now unfortunately I don't have access to any old PASemi hardware and
cannot confirm that my changes haven't broken anything for those.
I believe Hector was in contact with Olof a few months ago who
said that he might still have an old machine on which he could
test this.
I'd very much appreciate if he (or anyone else for that matter :-)) 
could give this series a quick test on the old PASemi machines.



Sven Peter (10):
  dt-bindings: i2c: Add Apple I2C controller bindings
  i2c: pasemi: Use io{read,write}32
  i2c: pasemi: Remove usage of pci_dev
  i2c: pasemi: Split off common probing code
  i2c: pasemi: Split pci driver to its own file
  i2c: pasemi: Move common reset code to own function
  i2c: pasemi: Allow to configure bus frequency
  i2c: pasemi: Refactor _probe to use devm_*
  i2c: pasemi: Add Apple platform driver
  i2c: pasemi: Set enable bit for Apple variant

 .../devicetree/bindings/i2c/apple,i2c.yaml    |  61 +++++++++
 MAINTAINERS                                   |   2 +
 drivers/i2c/busses/Kconfig                    |  11 ++
 drivers/i2c/busses/Makefile                   |   3 +
 drivers/i2c/busses/i2c-pasemi-apple.c         | 122 ++++++++++++++++++
 .../{i2c-pasemi.c => i2c-pasemi-core.c}       | 114 +++++-----------
 drivers/i2c/busses/i2c-pasemi-core.h          |  21 +++
 drivers/i2c/busses/i2c-pasemi-pci.c           |  85 ++++++++++++
 8 files changed, 334 insertions(+), 85 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/i2c/apple,i2c.yaml
 create mode 100644 drivers/i2c/busses/i2c-pasemi-apple.c
 rename drivers/i2c/busses/{i2c-pasemi.c => i2c-pasemi-core.c} (77%)
 create mode 100644 drivers/i2c/busses/i2c-pasemi-core.h
 create mode 100644 drivers/i2c/busses/i2c-pasemi-pci.c


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