[PATCH v8 0/2] riscv: spacemit: add i2c support to K1 SoC

[Troy Mitchell <troymitchell988@gmail.com>]

Hi all,

This patch implements I2C driver for the SpacemiT K1 SoC,
providing basic support for I2C read/write communication which
compatible with standard I2C bus specifications.

In this version, the driver defaults to use fast-speed-mode and
interrupts for transmission, and does not support DMA, high-speed mode, or FIFO.

The docs of I2C can be found here, in chapter 16.1 I2C [1]

Link: https://developer.spacemit.com/documentation?token=Rn9Kw3iFHirAMgkIpTAcV2Arnkf#part5 [1]
---
Changes in v8:
- Patch #2:
        - Fix code style
        - Fix comment style
- Link to v7: https://lore.kernel.org/r/20250316-k1-i2c-master-v7-0-f2d5c43e2f40@gmail.com

Changes in v7:
- Patch #2:
        - Adjust structure member types  
        - Default to 400,000 Hz if `clock-frequency` is unavailable  
        - Fix code style
        - Fix comments  
        - Kconfig: Rename "Spacemit" to "SpacemiT"  
        - Use local variables in `spacemit_xfer_msgs`
        - Rename `spacemit_i2c_wait_bus_busy` to `spacemit_i2c_wait_bus_idle`
        - Reduce transmission timeout in `spacemit_i2c_calc_timeout`  
Link to v6:
https://lore.kernel.org/r/20250307-k1-i2c-master-v6-0-34f17d2dae1c@gmail.com

Change in v6:
- Patch #1:
        - Give a brief clock description and a clear clock name
        - Changed the clock numbers in the example to match those
          in the mainline clock driver
- Patch #2:
        - Fix incorrect comments in macro definitions
        - Fix code style
        - Merge `spacemit_i2c_xfer_core` into `spacemit_i2c_xfer`
        - Remove `reset` and `enable_irq` before each transfer
          and place `reset` in the probe function.
        - SPACEMIT_I2C_GET_ERR -> SPACEMIT_I2C_SR_ERR
        - spacemit_i2c_recover_bus_busy -> spacemit_i2c_wait_bus_busy
        - Support standard mode
Link to v5:
https://lore.kernel.org/all/20250303-k1-i2c-master-v5-0-21dfc7adfe37@gmail.com/

Change in v5:
- Patch #1:
        - Add `clock-names` property
        - Modify the clock property into two
- Patch #2:
        - Enable the APB clock
        - Fix comment and code styles
        - Fix typo and drop unnecessary description in Kconfig
        - Prefix all macro definitions with SPACEMIT_
        - Rename `spacemit_i2c_bus_reset` to `spacemit_i2c_conditionally_reset_bus`
        - Remove all `unlikely` and `likely`
        - Remove unused register and bit macros
        - Remove the "err" field, as it only contains a subset of the status field
        - Retrieve `clock-frequency` from the device tree instead of using a macro
        - Use a local variable to track the current message
        - Use `i2c->read` to represent read and write statuses instead of `i2c->dir`
Link to v4:
https://lore.kernel.org/all/20241125-k1-i2c-master-v4-0-0f3d5886336b@gmail.com/

Change in v4:
- Patch #1:
	- Change the default value of clock-frequency from 100000 to
	  400000. This is to correspond to the driver's default value.
	- Drop the minimum of clock-frequency
	- Modify the description of clock-frequency
- Patch #2:
	- Drop the `inline` qualifier from the `spacemit_i2c_xfer_core` function
	- Drop the initialization of `ret` to 0 in `spacemit_i2c_xfer_core` function
	- Drop useless wrap
Link to v3:
https://lore.kernel.org/all/20241112-k1-i2c-master-v3-0-5005b70dc208@gmail.com/

Change in v3:
- Patch #1:
	- Change the maxItems of reg from 2 to 1 in properties
	- Modify reg in dts example
	- Changed the enum selection for clock-frequency to a range,
	  setting a minimum value of 1 and a maximum value of 3,300,000.
- Patch #2:
	- Drop unused judgement in `spacemit_i2c_xfer_msg`
	- Fix the dangling else warning in `spacemit_i2c_is_last_msg`
	- Fix the error check for `i2c->base`
	- Modify Kconfig dependencies
Link to v2:
https://lore.kernel.org/all/20241028053220.346283-1-TroyMitchell988@gmail.com/

Change in v2:
- Patch #1:
	- Change the maxItems of reg from 1 to 2 in properties
	- Change 'i2c' to 'I2C' in the commit message.
	- Drop fifo-disable property
	- Drop alias in dts example
	- Move `unevaluatedProperties` after `required:` block
- Patch #2:
	- Alphabetize Makefile and Kconfig
	- Change `.remove_new` to `.remove` in `struct platform_driver`
	- Change `dev_alert` to `dev_warn_ratelimited` in `spacemit_i2c_bus_reset`
	- Change `spacemit_i2c_read/write_reg` to `read/writel`
	- Change `spacemit_i2c_dt_match` to `spacemit_i2c_of_match`
	- Clean up code flow
	- Fix unnecessary line wraps
	- Move `spacemit_i2c_handle_err` to a suitable location
	- Modify Kconfig dependencies
	- Use `PTR_ERR(i2c->base)` directly as the `dev_err_probe` parameter instead of
	  the intermediate variable
Link to v1:
https://lore.kernel.org/all/20241015075134.1449458-1-TroyMitchell988@gmail.com/

---
Troy Mitchell (2):
      dt-bindings: i2c: spacemit: add support for K1 SoC
      i2c: spacemit: add support for SpacemiT K1 SoC

 .../devicetree/bindings/i2c/spacemit,k1-i2c.yaml   |  61 +++
 drivers/i2c/busses/Kconfig                         |  17 +
 drivers/i2c/busses/Makefile                        |   1 +
 drivers/i2c/busses/i2c-k1.c                        | 602 +++++++++++++++++++++
 4 files changed, 681 insertions(+)
---
base-commit: 8e929cb546ee42c9a61d24fae60605e9e3192354
change-id: 20241031-k1-i2c-master-fe7f7b0dce93
prerequisite-change-id: 20240626-k1-01-basic-dt-1aa31eeebcd2:v5
prerequisite-patch-id: 47dcf6861f7d434d25855b379e6d7ef4ce369c9c
prerequisite-patch-id: 77787fe82911923aff15ccf565e8fa451538c3a6
prerequisite-patch-id: b0bdb1742d96c5738f05262c3b0059102761390b
prerequisite-patch-id: 3927d39d8d77e35d5bfe53d9950da574ff8f2054
prerequisite-patch-id: a98039136a4796252a6029e474f03906f2541643
prerequisite-patch-id: c95f6dc0547a2a63a76e3cba0cf5c623b212b4e6
prerequisite-patch-id: 66e750e438ee959ddc2a6f0650814a2d8c989139
prerequisite-patch-id: 29a0fd8c36c1a4340f0d0b68a4c34d2b8abfb1ab
prerequisite-patch-id: 0bdfff661c33c380d1cf00a6c68688e05f88c0b3
prerequisite-patch-id: 99f15718e0bfbb7ed1a96dfa19f35841b004dae9

Best regards,
-- 
Troy Mitchell <troymitchell988@gmail.com>