Subject: [PATCH v30 0/5] Add ASPEED AST2600 I2C controller driver

From: Ryan Chen <[email-masked]>
Date: Thu, 28 May 2026 15:41:35 +0800

This series adds support for the AST2600 I2C controller “new register
set” implementation.

The AST2600 I2C controller introduces a revised register layout which
separates controller and target functionality into distinct register
blocks, and extends clock divider configuration and packet-based
transfer support compared to the legacy mixed register layout used on
earlier ASPEED SoCs.

The current driver implementation for the AST2600 I2C peripheral is
through the hardware's "compatibility mode", which exposes a register
set that matches the previous generation hardware (AST2500 and earlier).

Instead, add a driver that works in new-register-set mode, to allow the
new features, and will provide support for future hardware that will
not implement compatibility mode.

In order to support the new mode, we need a DT binding change to
reflect the reference to the global register set. Since the binding
still represents the same (AST2600 SoC) physical hardware, we continue
to use the existing compatible string of "aspeed,ast2600-i2c-bus".

However: since we're changing semantics for an existing binding, we
allow backwards compatibility by selecting on presence/absence of the
newly-added properties, and fall back to the old driver (ie., in
compatibility mode) when we detect a DT using the old binding spec.

Specifically:

- ast2600-i2c-bus nodes that provide the `aspeed,global-regs` property
  (present in the new binding and absent in the legacy binding) will be
  successfully probed by the new driver

- ast2600-i2c-bus nodes without `aspeed,global-regs` continue to use the
  existing driver (in legacy register mode), ensuring that platforms
  with the current DTBs remain functional

Signed-off-by: Ryan Chen <[email-masked]>
---
Changes in v30:
- 1/5: aspeed,ast2600-i2c.yaml: keep backward compatibility for
  existing in-tree AST2600 device trees (Sashiko AI review).
  - reg: add minItems: 1 so legacy single-reg DTs still validate.
  - retain bus-frequency as a deprecated property so DTs that still
    use it are not rejected by unevaluatedProperties: false.
- 2/5: new patch "i2c: aspeed: Read clock-frequency via
  i2c_parse_fw_timings()". The legacy i2c-aspeed driver now reads
  the standard clock-frequency property first and falls back to
  bus-frequency, avoiding a silent 100 kHz downgrade when a DT
  follows the updated binding but still binds to the legacy
  driver (Sashiko AI review).
- 4/5: address Sashiko AI code review feedback:
  - Use manual i2c_add_adapter() / i2c_del_adapter() instead of
    devm_i2c_add_adapter() so the adapter is torn down before the
    hardware is disabled in remove(); otherwise client .remove()
    callbacks can fail or hang after FUN_CTRL/IER have been cleared.
  - synchronize_irq() and clear pending IRQ status on the controller
    timeout path to avoid the ISR racing with the next transfer and
    touching freed msgs.
  - Use clamp_t() for AC TIMING divisor / scl_low / scl_high so
    extreme clock-frequency values cannot underflow into the unsigned
    domain and corrupt the AC TIMING register.
  - Derive the RX buffer offset from buf_size instead of hardcoding
    0x10, since the dual-pool split is configurable.
  - Clamp i2c-scl-clk-low-timeout-us to the TTIMEOUT field's 5-bit
    range (max 31 * 1024us) and emit a dev_warn() instead of letting
    AST2600_I2CC_TTIMEOUT()'s mask silently truncate larger values.
  - Return -EBUSY (not -ENOMEM) for every ast2600_i2c_do_start()
    failure path in the controller packet IRQ handler (NORMAL_STOP,
    TX_ACK, and RX_DONE branches).
  - Advertise I2C_AQ_NO_ZERO_LEN_READ via i2c_adapter_quirks so the
    i2c-core rejects zero-byte reads before they reach the driver.
    The AST2600 packet engine cannot encode a zero-length RX command
    and would otherwise stall waiting for an RX_DONE that never
    arrives.
- 5/5: address Sashiko AI code review feedback:
  - Force-stop path (target IRQ aborting an in-flight controller
    transfer): disable the controller IER and W1C-clear pending ISR
    before calling complete(), then restore the IER after the
    wake-up. Without the disable/clear sequence the controller IRQ
    handler can race with the target abort path and double-complete
    or touch freed msgs.
  - unreg_target() teardown ordering: disable the target IER first,
    then disable SLAVE_EN / clear ADDR_CTRL, synchronize_irq(), W1C
    pending ISR, and only then NULL i2c_bus->target and clear
    target_active. The old order left IER enabled while target was
    being cleared, allowing an in-flight handler to dereference a
    target pointer the caller had already freed.
  - reg_target() bring-up ordering: assign i2c_bus->target before
    enabling SLAVE_EN. Otherwise an IRQ that fires after SLAVE_EN
    is set but before the pointer is stored finds target == NULL,
    exits without clearing the ISR, and the unmasked event re-fires
    as an IRQ storm.
  - Use writel() instead of writeb() when staging a TX byte into
    the target buffer. The AST2600 buffer SRAM only supports 32-bit
    accesses; byte writes are silently dropped (or, on some
    revisions, raise a bus fault), so a SLAVE_READ_REQUESTED reply
    never reaches the master.
  - reg_target() rejects 10-bit client addresses with
    -EAFNOSUPPORT. AST2600_I2CS_ADDR1 is only a 7-bit field;
    without the check, the high bits of a 10-bit address overflow
    into the adjacent ADDR2 field and silently corrupt a second
    target slot.
  - Initialise the local `u8 value` to 0 in the target packet IRQ
    handler. Its address is passed to i2c_slave_event() for events
    such as I2C_SLAVE_STOP / I2C_SLAVE_READ_REQUESTED; a slave
    backend that reads the byte before writing would otherwise leak
    uninitialised kernel stack.
- Link to v29: https://lore.kernel.org/r/[email-masked]

Changes in v29:
- 2/4: remove aspeed,enable-dma properties.
- 3/4: update commit message remove transfer mode selection.
- 3/4: remove sysfs file.
- 3/4: remove define I2C_TARGET_MSG_BUF_SIZE and AST2600_I2C_DMA_SIZE.
- 3/4: remove buf_index in struct ast2600_i2c_bus.
- 3/4, 4/4: remove dma/byte mode, use buffer mode only.
- 4/4: fix race between unreg_target and IRQ handler.
- 4/4: move i2cs ier enable from ast2600_i2c_init to probe after master ier enable.
- Link to v28: https://lore.kernel.org/r/[email-masked]

Changes in v28:
- 2/4: update commit message correspond with aspeed,enable-dma.
- 2/4: remove aspeed,transfer-mode and add aspeed,enable-dma property
  and description.
- 2/4: Fix aspeed,enable-dma description to reflect hardware capability
  rather than software behavior.
- 3/4: Separate xfer_mode_store into distinct parse and availability-check
  steps by introducing ast2600_i2c_xfer_mode_check().
- 3/4: fix tx dma memcpy source point address.
- 3/4: Use a temporary variable for devm_platform_get_and_ioremap_resource()
  to avoid storing an ERR_PTR in i2c_bus->buf_base; drop the redundant
  NULL assignment in the error path since i2c_bus is kzalloc()ed.
- 3/4: Add ABI documentation file
  Documentation/ABI/testing/sysfs-driver-ast2600-i2c.
- 4/4: fix typo condication -> condition.
- 4/4: fix compile error, when disable CONFIG_I2C_SLAVE.
- Link to v27: https://lore.kernel.org/r/[email-masked]

Changes in v27:
- 1/4 use aspeed,enable-dma instead aspeed,transfer-mode.
- 2/4 remove aspeed,transfer-mode selection instad aspeed,transfer-mode
- 2/4 add sysfs for xfer mode.
- Link to v26: https://lore.kernel.org/r/[email-masked]

Changes in v26:
- 1/4: binding reworks based on review feedback
- Link to v25: https://lore.kernel.org/r/[email-masked]

Changes in v25:
- Use b4 to send series.
- Rebase on v7.0-rc1.
- Clarify cover letter and commit logs based on review feedback.
- Remove the i2c-aspeed-core multiplexer infrastructure and
  implement driver selection via conditional -ENODEV handling
  in individual probe() functions.
- 3/4: incorporate review feedback and refactor new driver
- Link to v24: https://lore.kernel.org/r/[email-masked]

Changes in v24:
- aspeed,ast2600-i2c.yaml
 - fix make dt_binding_check blank warning.
- Link to v23: https://lore.kernel.org/all/[email-masked]/

Changes in v23:
- update typo patch (1/4) commit message.
- aspeed,ast2600-i2c.yaml
 - update reg and description.
- i2c-ast2600.c controller
 - replace ast2600_select_i2c_clock to ast2600_i2c_ac_timing_config.
- i2c-ast2600.c target
 - I2C_TARGET_MSG_BUF_SIZE 256 to 4096
 - remove blank line.
 - refine Master comment description to controller
- Link to v22: https://lore.kernel.org/all/[email-masked]/

Changes in v22:
- update patch (1/4) commit message add dts example reason.
- aspeed,ast2600-i2c.yaml @patch (1/4)
 - rename ast2600-i2c.yaml to aspeed,ast2600-i2c.yaml.
 - update reg, clock-frequency description.
- aspeed,ast2600-i2c.yaml @patch (2/4)
 - aspeed,transfer-mode, aspeed,transfer-mode add for ast2600.
- i2c-aspeed-core.c,h @patch (3/4)
 - add i2c-aspeed-core allow both old and new device trees using the
   same compatible string "aspeed,ast2600-i2c-bus".
- Link to v21: https://lore.kernel.org/all/[email-masked]/

Changes in v21:
- update patch (1/4) commit message
- i2c-ast2600.c
 - move rst to local variable in ast2600_i2c_probe().
- Link to v20: https://lore.kernel.org/all/[email-masked]/

Changes in v20:
- ast2600-i2c.yaml
 - fix warning at make dt_binding_check.
- Link to v19: https://lore.kernel.org/all/[email-masked]/

Changes in v19:
- Split AST2600 binding into its own YAML file
 - Removed `aspeed,ast2600-i2c-bus` from `aspeed,i2c.yaml`
 - Added `aspeed,global-regs` and `aspeed,transfer-mode` to AST2600 binding
- Link to v18: https://lore.kernel.org/all/[email-masked]/

Changes in v18:
- refine patch (1/3) commit message (reason for commit not list.)
- i2c-ast2600.c
 - remove redundant reset_control_deassert in driver probe.
 - remove reset_control_assert(i2c_bus->rst) in driver remove.
- Link to v17: https://lore.kernel.org/all/[email-masked]/

Changes in v17:
- move i2c new mode register and feature into driver commit message.
- aspeed,i2c.yaml
 - remove multi-master properties.
 - use aspeed,transfer-mode properties for aspeed,enable-byte/enable-dma.
-i2c-ast2600.c
 - rename dma_safe_buf to controller_dma_safe_buf.
 - fix ast2600_i2c_recover_bus return overflow warnings.
 - add ast2600_i2c_target_packet_buff_irq unhandle case.
 - add parameter "cmd" in ast2600_i2c_setup_dma_rx,
   ast2600_i2c_setup_buff_rx, ast2600_i2c_setup_byte_rx
 - use reset_control_deassert replace
   devm_reset_control_get_shared_deasserted.
 - useaspeed,transfer-mode properties for transfer mode setting.
 - change compatible = "aspeed,ast2600-i2cv2" to "aspeed,ast2600-i2c-bus".
- Link to v16: https://lore.kernel.org/all/[email-masked]/

Changes in v16:
- aspeed,i2c.yaml: add aspeed,enable-byte properties for force byte mode.
- i2c-ast2600.c
 - change include asm/unaligned.h to linux/unaligned.h.
 - add reset timeout councter when slave active timeout.
 - modify issue i2c_recovery_bus before slave re-enable.
 - add aspeed,enable-byte properties.
- Link to v15: https://lore.kernel.org/all/[email-masked]/

Changes in v15:
- i2c-ast2600.c
 - add include unaligned.h
 - rename all master -> controller, slave -> target.
 - keep multi-master to align property.
 - remove no used element in ast2600_i2c_bus.
- Link to v14: https://lore.kernel.org/all/[email-masked]/

Changes in v14:
- aspeed,i2c.yaml
 - v13 change people reviewed-by tag, v14 fixed to original people tag,
   modify to Reviewed-by: Krzysztof Kozlowski <[email-masked]>
 - struct ast2600_i2c_bus layout optimal.
 - ast2600_select_i2c_clock refine.
 - ast2600_i2c_recover_bus overridden fix.
 - dma_mapping_error() returned error code shadowed modify.
 - buffer register in a 4-byte aligned simplified
 - remove smbus alert
- Link to v13: https://lore.kernel.org/all/[email-masked]/

Changes in v13:
 - separate i2c master and slave driver to be two patchs.
 - modify include header list, add bits.h include. remove of*.h
 - modify (((x) >> 24) & GENMASK(5, 0)) to (((x) & GENMASK(29, 24)) >> 24)
 - modify ast2600_select_i2c_clock function implement.
 - modify ast2600_i2c_recover_bus function u32 claim to
   u32 state = readl(i2c_bus->reg_base + AST2600_I2CC_STS_AND_BUFF);
- Link to v12: https://lore.kernel.org/all/[email-masked]/

Changes in v12:
- aspeed,i2c.yaml
 - add Reviewed-by: Krzysztof Kozlowski <[email-masked]>
- i2c-ast2600.c
 - update include by alphabetical order
 - make just a one TAB and put the last two lines on the single one
 - remove no used timing_table structre
 - remove enum explicit assinment
 - rewritten to avoid this and using loop in ast2600_select_i2c_clock
 - use GENMASK for most 0xffff
 - remove too many parentheses
 - use str_read_write replace read write string
 - remove redundant blank line after ast2600_i2c_bus_of_table
 - fix wrong multi-line style of the comment
 - use macro for i2c standard speeds
 - remove useless noise dev_info
- Link to v11: https://lore.kernel.org/all/[email-masked]/

Changes in v11:
- aspeed,i2c.yaml
 - no change, the same with v10.
- i2c-ast2600.c
 - modify alert_enable from int -> boolean.
 - modify dbg string recovery -> recover.
 - remove no need to init 0.
 - remove new line after break.
 - remove unneeded empty line.
 - modify dma_alloc_coherent to dmam_alloc_coherent
 - modify probe nomem return dev_err_probe
 - modify i2c_add_adapter to devm_i2c_adapter
 - modify checkpatch: Alignment should match open parenthesis
 - modify checkpatch: braces {} should be used on all arms of this statement
 - modify checkpatch: Unbalanced braces around else statement
- Link to v10: https://lore.kernel.org/all/[email-masked]/

Changes in v10:
- aspeed,i2c.yaml
 - move unevaluatedProperties after allOf.
 - remove extra one blank line.
- i2c-ast2600.c
 - no change, the same with v8.
- Link to v9: https://lore.kernel.org/all/[email-masked]/

Changes in v9:
- aspeed,i2c.yaml
 - backoff to v7.
  - no fix typo in maintainer's name and email. this would be another patch.
  - no remove address-cells, size-cells, this would be another patch.
 - use aspeed,enable-dma property instead of aspeed,xfer-mode selection.
 - fix allOf and else false properties for aspeed,ast2600-i2cv2.
- i2c-ast2600.c
 - no change, the same with v8
- Link to v8: https://lore.kernel.org/all/[email-masked]/

Changes in v8:
- aspeed,i2c.yaml
 - modify commit message.
 - Fix typo in maintainer's name and email.
 - remove address-cells, size-cells.
- i2c-ast2600.c
 - move "i2c timeout counter" comment description before property_read.
 - remove redundant code "return ret" in probe end.
- Link to v7: https://lore.kernel.org/all/[email-masked]/

Changes in v7:
- aspeed,i2c.yaml
 - Update ASPEED I2C maintainers email.
 - use aspeed,enable-dma property instead of aspeed,xfer-mode selection.
 - fix allOf and else false properties for aspeed,ast2600-i2cv2.
- i2c-ast2600.c
 - remove aspeed,xfer-mode instead of aspeed,enable-dma mode. buffer mode
   is default.
 - remove aspeed,timeout instead of i2c-scl-clk-low-timeout-us for
   timeout setting.
- Link to v6: https://lore.kernel.org/all/[email-masked]/

Changes in v6:
- remove aspeed,i2cv2.yaml, merge to aspeed,i2c.yaml -add support for
  i2cv2 properites.
- i2c-ast2600.c
 - fix ast2600_i2c_remove ordering.
 - remove ast2600_i2c_probe goto labels, and add dev_err_probe -remove
   redundant deb_dbg debug message.
 - rename gr_regmap -> global_regs
- Link to v5: https://lore.kernel.org/all/[email-masked]/

Changes in v5:
- remove ast2600-i2c-global.yaml, i2c-ast2600-global.c.
- i2c-ast2600.c
 - remove legacy clock divide, all go for new clock divide.
 - remove duplicated read isr.
 - remove no used driver match
 - fix probe return for each labels return.
 - global use mfd driver, driver use phandle to regmap read/write.
- rename aspeed,i2c-ast2600.yaml to aspeed,i2cv2.yaml -remove bus-frequency.
- add required aspeed,gr
- add timeout, byte-mode, buff-mode properites.
- Link to v4: https://lore.kernel.org/all/[email-masked]/

Changes in v4:
- fix i2c-ast2600.c driver buffer mode use single buffer conflit in
  master slave mode both enable.
- fix kmemleak issue when use dma mode.
- fix typo aspeed,i2c-ast2600.yaml compatible is "aspeed,ast2600-i2c"
- fix typo aspeed,i2c-ast2600.ymal to aspeed,i2c-ast2600.yaml
- Link to v3: https://lore.kernel.org/all/[email-masked]/

Changes in v3:
- fix i2c global clock divide default value.
- remove i2c slave no used dev_dbg info.
- Link to v2: https://lore.kernel.org/all/[email-masked]/

Changes in v2:
- add i2c global ymal file commit.
- rename file name from new to ast2600.
  aspeed-i2c-new-global.c -> i2c-ast2600-global.c
  aspeed-i2c-new-global.h -> i2c-ast2600-global.h
  i2c-new-aspeed.c -> i2c-ast2600.c
- rename all driver function name to ast2600.
- Link to v1: https://lore.kernel.org/all/[email-masked]/

---
Ryan Chen (5):
      dt-bindings: i2c: Split AST2600 binding into a new YAML
      i2c: aspeed: Read clock-frequency via i2c_parse_fw_timings()
      dt-bindings: i2c: ast2600-i2c.yaml: Add global-regs properties
      i2c: ast2600: Add controller driver for AST2600 new register set
      i2c: ast2600: Add target mode support

 .../bindings/i2c/aspeed,ast2600-i2c.yaml           |   80 ++
 .../devicetree/bindings/i2c/aspeed,i2c.yaml        |    3 +-
 drivers/i2c/busses/Makefile                        |    2 +-
 drivers/i2c/busses/i2c-aspeed.c                    |   24 +-
 drivers/i2c/busses/i2c-ast2600.c                   | 1186 ++++++++++++++++++++
 5 files changed, 1286 insertions(+), 9 deletions(-)
---
base-commit: a293ec25d59dd96309058c70df5a4dd0f889a1e4
change-id: 20260223-upstream_i2c-ebd07f89739c

Best regards,
-- 
Ryan Chen <[email-masked]>