[PATCH v2 0/7] Add Mule I2C multiplexer support

[Farouk Bouabid]

Mule is an mcu that emulates a set of i2c devices which are reachable
through an i2c-mux.

The emulated devices share a single i2c address with the mux core itself
where the requested register is what determines which logic is executed
(muxing logic or device logic):

1- The devices on the mux core can be selected (muxing functionality) by
writing the appropriate device number to an i2c config register (0xff)
that is not used by any device logic.

2- Any access to a register other than the config register will be
handled by the previously selected device.

      +-------------------------------------------------------+
      |  Mule                                                 |
      |        +---------------+                              |
    ----+-(1)->|Config register|-----+                        |
      | |      +---------------+     |                        |
      | |                            V_                       |
      | |                            |  \          +--------+ |
      | |                            |   \-------->| dev #0 | |
      | |                            |   |         +--------+ |
      | |                            | M |-------->| dev #1 | |
      | +-----------(2)------------->| U |         +--------+ |
      |                              | X |-------->| dev #2 | |
      |                              |   |         +--------+ |
      |                              |   /-------->| dev #3 | |
      |                              |__/          +--------+ |
      +-------------------------------------------------------+

The current i2c-mux implementation does not allow the mux core to use the
i2c address of a child device. As a workaround, A new i2c-adapter quirk is
introduced to skip the check for conflict between a child device and the
mux core i2c address when adding the child device.

This patch-series adds support for this multiplexer. Mule is integrated
as part of rk3399-puma, px30-ringneck, rk3588-tiger and rk3588-jaguar
boards.

To: Wolfram Sang <wsa+renesas at sang-engineering.com>
To: Peter Rosin <peda at axentia.se>
To: Andi Shyti <andi.shyti at kernel.org>
To: Rob Herring <robh at kernel.org>
To: Krzysztof Kozlowski <krzysztof.kozlowski+dt at linaro.org>
To: Conor Dooley <conor+dt at kernel.org>
To: Quentin Schulz <quentin.schulz at theobroma-systems.com>
To: Heiko Stuebner <heiko at sntech.de>
To: Quentin Schulz <quentin.schulz at cherry.de>
Cc: linux-i2c at vger.kernel.org
Cc: linux-kernel at vger.kernel.org
Cc: devicetree at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-rockchip at lists.infradead.org
Signed-off-by: Farouk Bouabid <farouk.bouabid at cherry.de>

Changes in v2:
- Add i2c-adapter quirks to skip checking for conflict between the mux core
  and a child device address.
- Rename dt-binding to "tsd,mule-i2c-mux.yaml"
- Add Mule description to kconfig
- Fix indentation
- Move device table after probe

- Link to v1: https://lore.kernel.org/r/20240426-dev-mule-i2c-mux-v1-0-045a482f6ffb@theobroma-systems.com

---
Farouk Bouabid (7):
      i2c: mux: add the ability to share mux core address with child nodes
      dt-bindings: i2c: mux: mule: add dt-bindings for mule i2c multiplexer
      i2c: muxes: add support for mule i2c multiplexer
      arm64: dts: rockchip: add mule i2c mux (0x18) on rk3399-puma
      arm64: dts: rockchip: add mule i2c mux (0x18) on rk3588-tiger
      arm64: dts: rockchip: add mule i2c mux (0x18) on px30-ringneck
      arm64: dts: rockchip: add mule i2c mux (0x18) on rk3588-jaguar

 .../devicetree/bindings/i2c/tsd,mule-i2c-mux.yaml  |  80 +++++++++++
 arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi    |  20 ++-
 arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi      |  20 ++-
 arch/arm64/boot/dts/rockchip/rk3588-jaguar.dts     |  19 ++-
 arch/arm64/boot/dts/rockchip/rk3588-tiger.dtsi     |  19 ++-
 drivers/i2c/i2c-core-base.c                        |   6 +-
 drivers/i2c/i2c-mux.c                              |  25 +++-
 drivers/i2c/muxes/Kconfig                          |  18 +++
 drivers/i2c/muxes/Makefile                         |   1 +
 drivers/i2c/muxes/i2c-mux-mule.c                   | 157 +++++++++++++++++++++
 include/linux/i2c-mux.h                            |   1 +
 include/linux/i2c.h                                |   7 +
 12 files changed, 361 insertions(+), 12 deletions(-)
---
base-commit: 23918f4e52d072b96a4d909e91298b8dd6ad4325
change-id: 20240404-dev-mule-i2c-mux-9103cde07021

Best regards,
-- 
Farouk Bouabid <farouk.bouabid at cherry.de>