[PATCH v3 0/2] Add Qualcomm I2C target controller driver

QDU1000 and related Qualcomm SoCs include a dedicated I2C target
controller that operates exclusively in target mode and is not supported
by the existing Qualcomm I2C master controller drivers (GENI, QUP).

This series adds DT binding and driver support for this IP. The driver
uses the standard Linux I2C slave framework (reg_target/unreg_target,
i2c_slave_event) so any slave backend (e.g. slave-24c02) can be
attached via i2c_slave_register().

The series is structured as follows:

  Patch 1: DT binding document
  Patch 2: Driver implementation including Kconfig, Makefile and
           MAINTAINERS entries

The driver has been tested on QDU1000 hardware.

Signed-off-by: Viken Dadhaniya <[email protected]>
---
Changes in v3:
- Rename file to match compatible (qcom,qdu1000-i2c-target.yaml)
- Remove interconnect-names property
- Remove allOf reference to i2c-controller.yaml
- Remove #address-cells and #size-cells from example
- Add minItems: 1 to pinctrl-names
- Move I2C_S_CORE_EN out of hw_init; enable core only in reg_slave
  and hw_reset
- Add usleep_range(10, 20) after SW_RESET before reconfiguring hardware 
- Fix RESTART_DETECTED dispatch order; handle before STRCH_RD and
  Rx data phases
- Use test_and_set_bit in write_requested and handle_strch_rd
- Loop drain_rx_fifo until FIFO is empty to close post-STOP data race
- Disable core before clearing slave pointer in unreg_slave
- Clear target->status on resume
- Switch from devm_clk_get_enabled to devm_clk_get with manual
  clk_prepare_enable
- Remove unbalanced disable_irq from remove
- Update struct kdoc to note I2C_LOCK_ROOT_ADAPTER serialises
  reg/unreg_target
- Link to v2: https://patch.msgid.link/[email protected]

Changes in v2:
- Rename driver and binding from "slave" to "target" terminology
- Use SoC-specific compatible string (qcom,qdu1000-i2c-target) instead of
  generic qcom,i2c-slave; add allOf/$ref to i2c-controller.yaml
- Replace SMBus layer (smbus_xfer, I2C_FUNC_SMBUS_*) with native Linux I2C
  slave framework (reg_target/unreg_target, I2C_SLAVE_* events)
- Remove qcom,slave-addr DT property; slave address taken from the
  registered i2c_client at reg_target() time
- Remove staging buffers and spinlock; bytes delivered directly to backend
  via i2c_slave_event() per STRCH_RD/RX/STOP event
- Use SET_NOIRQ_SYSTEM_SLEEP_PM_OPS; PM core quiesces IRQs at noirq stage,
  removing need for manual disable_irq/enable_irq in suspend
- Simplify clock-names (xo/ahb) and interconnect-names (i2c)
- Replace icc_enable/icc_disable with icc_set_bw() vote/unvote
- Merge MAINTAINERS entry into the dt-bindings patch
- Link to v1: https://patch.msgid.link/[email protected]

---
Viken Dadhaniya (2):
      dt-bindings: i2c: Add Qualcomm I2C target controller
      i2c: qcom-target: Add driver for Qualcomm I2C target controller

 .../bindings/i2c/qcom,qdu1000-i2c-target.yaml      |  75 +++
 MAINTAINERS                                        |   9 +
 drivers/i2c/busses/Kconfig                         |  15 +
 drivers/i2c/busses/Makefile                        |   1 +
 drivers/i2c/busses/i2c-qcom-target.c               | 588 +++++++++++++++++++++
 5 files changed, 688 insertions(+)
---
base-commit: 415606a7be939835db9b0d6b711887586646346d
change-id: 20260628-i2c-qcom-slave-c382ff4e8691

Best regards,
--  
Viken Dadhaniya <[email protected]>