Re: [PATCH v1 0/3] i2c: dwc: Add I2C DWC master/slave support for StarFive JHB100

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Hi,

On Thu, May 21, 2026 at 11:43:37AM +0800, lianfeng.ouyang wrote:
> From: Lianfeng Ouyang <lianfeng.ouyang@starfivetech.com>
> 
> The Synopsys DesignWare Core (DWC) I2C controller is a variant of the
> widely-used DesignWare I2C IP, with a distinct register layout and
> enhanced features such as SMBus Alert and programmable FIFO depths.

I wonder why they did shuffle the registers... :(

> This patch series introduces support for this controller as implemented
> on the StarFive JHB100 platform, which utilizes it for both master and
> slave operations (e.g., for MCTP over I2C).
> 
> The series is structured as follows:
> 1.  Adds the device tree binding document for the snps,dwc-i2c compatible.
> 2.  Prepares the existing i2c-designware-core by exporting and making
>     certain key functions overridable, allowing code reuse.
> 3.  Introduces the new i2c-dwc-core driver, with separate modules for
>     master and slave functionality, based on the 2023-07 revision of the
>     Synopsys IP manual.
> 
> Key differences from the Existing i2c-designware Driver
> 1.  The DWC IP's offsets for all key registers are redefined. The driver
>     maps to the correct addresses by overriding macros from the core
>     header file in a new header (i2c-dwc-core.h).

Instead of this, can you provide a regmap that internally maps to these
shuffled registers?

> 2.  The host and slave of DWC IP need to perform probe callbacks
>     separately, so they cannot be directly set through i2c_dew_set_mode
> 3.  Interrupts are cleared by writing​ to the corresponding bits in the
>     INTR_CLRregister (write-1-to-clear).
> 4.  The DWC controller's IC_ENABLEregister contains an additional
>     TX_CMD_BLOCKcontrol bit. When enabling the controller, the driver must
>     ensure this bit is cleared. When disabling, only the ENABLEbit is
>     cleared, preserving other configurations.
> 
> Lianfeng Ouyang (3):
>   dt-bindings: i2c: snps,dwc-i2c: Add StarFive JHB100 bindings
>   i2c: designware: Export symbols and add __weak for DWC I2C driver
>   i2c: dwc: Add StarFive JHB100 I2C master/slave support
> 
>  .../devicetree/bindings/i2c/snps,dwc-i2c.yaml | 120 +++++
>  MAINTAINERS                                   |   7 +
>  drivers/i2c/busses/Kconfig                    |  34 ++
>  drivers/i2c/busses/Makefile                   |   3 +
>  drivers/i2c/busses/i2c-designware-common.c    |  57 ++-
>  drivers/i2c/busses/i2c-designware-core.h      |  25 +
>  drivers/i2c/busses/i2c-designware-master.c    |  14 +-
>  drivers/i2c/busses/i2c-designware-platdrv.c   |   6 +
>  drivers/i2c/busses/i2c-designware-slave.c     |   4 +-
>  drivers/i2c/busses/i2c-dwc-core.h             | 192 ++++++++
>  drivers/i2c/busses/i2c-dwc-master.c           | 441 ++++++++++++++++++
>  drivers/i2c/busses/i2c-dwc-slave.c            | 180 +++++++

Also the naming is confusing so if you need any glue code I recommend
calling it i2c-starfive-* instead.

>  12 files changed, 1068 insertions(+), 15 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/i2c/snps,dwc-i2c.yaml
>  create mode 100644 drivers/i2c/busses/i2c-dwc-core.h
>  create mode 100644 drivers/i2c/busses/i2c-dwc-master.c
>  create mode 100644 drivers/i2c/busses/i2c-dwc-slave.c
> 
> --
> 2.43.0