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[v8,0/2] mfd: add X-Powers AC200 support

Message ID 20260902-submit-ac200-mfd-v8-0-2aa06720b8ac@gmail.com (mailing list archive)
Headers
Series mfd: add X-Powers AC200 support |

Message

James Hilliard Sept. 2, 2026, 7:28 p.m. UTC 
The X-Powers AC200 is an I2C-controlled mixed-signal companion IC with
a paged register map shared by its audio, video, RTC and Fast Ethernet
PHY functions.

Add the parent binding and an I2C provider which enables and rate-locks
the shared input clock, initializes the paged regmap and controls the
common reset. Audio, video and RTC functions can be added as MFD
children.

The current regmap consumer is the separately submitted AC200/AC300
Ethernet PHY series:

  https://patch.msgid.link/20260818-submit-acx00-of-dynamic-v1-v9-0-b8c8d9ad0d83@gmail.com

The PHY remains enumerated on MDIO, its primary management bus. Its
AC200 package node follows the x-powers,ac200 phandle for ancillary I2C
register access, adds a managed device link and obtains the regmap with
dev_get_regmap(). This series and the PHY series can be merged in either
order; AC200 Ethernet support requires both.

This work builds on earlier AC200 work by Jernej Skrabec and Andre
Przywara:

  https://github.com/jernejsk/linux-1/commits/ac200-v4

Public AC200 documentation is linked from:

  https://linux-sunxi.org/AC200

Validation included an x86_64 W=1 object build, dt_binding_check, and a
combined W=1 build with the PHY series. On AC200 hardware, the provider
and PHY completed 100 overlapping bind cycles while preserving both
device links and recovering a 100 Mbps full-duplex link.

Assisted-by: Codex:gpt-5.6-sol
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
---
Changes v7 -> v8:
- identify the PHY series as the current regmap consumer
- describe future MFD children and the MDIO/I2C split
- store the regmap directly as driver data  (suggested by Lee Jones)
- reset the chip from the remove callback  (suggested by Lee Jones)
- drop the revision log and inherited-driver attribution  (suggested by Lee Jones)
- add Krzysztof's Reviewed-by tag to the binding
- rebase on the current MFD for-mfd-next branch
- Link to v7: https://patch.msgid.link/20260811-submit-ac200-mfd-v7-0-8b06f552a4d7@gmail.com

Changes v6 -> v7:
- drop the managed external-syscon helper and AC200 syscon registration
- leave the regmap attached to the I2C provider for direct device lookup
- reduce the MFD series from three patches to two
- Link to v6: https://patch.msgid.link/20260811-submit-ac200-mfd-v6-0-c5b1292c8498@gmail.com

Changes v5 -> v6:
- split the MFD work from the independently mergeable networking series
- put the merge routing and shared DT design at the start of the cover letter
- rebase on the MFD for-mfd-next branch
- Link to v5: https://patch.msgid.link/20260809-submit-acx00-of-dynamic-v1-v5-0-bfa1f8518b28@gmail.com

To: Lee Jones <lee@kernel.org>
To: Rob Herring <robh@kernel.org>
To: Krzysztof Kozlowski <krzk+dt@kernel.org>
To: Conor Dooley <conor+dt@kernel.org>
To: James Hilliard <james.hilliard1@gmail.com>
Cc: mfd@lists.linux.dev
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

---
James Hilliard (2):
      dt-bindings: mfd: x-powers: Add AC200
      mfd: ac200: Add X-Powers AC200 support

 .../devicetree/bindings/mfd/x-powers,ac200.yaml    |  49 ++++++++
 drivers/mfd/Kconfig                                |  11 ++
 drivers/mfd/Makefile                               |   1 +
 drivers/mfd/ac200.c                                | 136 +++++++++++++++++++++
 4 files changed, 197 insertions(+)
---
base-commit: 9d0e4b1ae5b045a2c92b0b9a1c3b268191c219d9
change-id: 20260811-submit-ac200-mfd-8bad6d09e285

Best regards,
--  
James Hilliard <james.hilliard1@gmail.com>

Comments

sashiko-bot@kernel.org Sept. 2, 2026, 7:40 p.m. UTC | #1 
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Unconditional global chip reset in shutdown/remove breaks RTC wake, Wake-on-LAN, and live PHY state.
--

commit d8592c963caa9b21487926208ea5815e059be1be
Author: James Hilliard <james.hilliard1@gmail.com>

mfd: ac200: Add X-Powers AC200 support
    
This commit adds support for the X-Powers AC200 mixed-signal companion IC.
It enables the shared input clock, initializes the paged regmap, and asserts
a chip reset during probe, driver removal, and system shutdown.

> diff --git a/drivers/mfd/ac200.c b/drivers/mfd/ac200.c
> new file mode 100644
> index 0000000000000..8445a460ef6c2
> --- /dev/null
> +++ b/drivers/mfd/ac200.c

[ ... ]

> +static void ac200_disable(struct regmap *regmap)
> +{
> +	regmap_write(regmap, AC200_SYS_CONTROL_REG, 0);
> +}

[Severity: High]
Does asserting a global chip reset here wipe the hardware state of all
co-packaged functions, including the RTC and Fast Ethernet PHY?

Since ac200_disable() is unconditionally called by ac200_shutdown() and
ac200_remove(), could this kill the PHY and clear the RTC during system
shutdown, breaking Wake-on-LAN and Wake-on-RTC from power-off states?

Furthermore, because the PHY is enumerated separately on the MDIO bus and
only references this MFD via a phandle, will unbinding the AC200 driver at
runtime (via ac200_remove) forcefully reset the PHY hardware out from under
the active MDIO PHY driver and lead to unpredictable network failures?

[ ... ]