Re: [PATCH net-next v8 2/4] net: pse-pd: add Realtek PSE MCU core

On Wed, 15 Jul 2026 07:55:26 +0000
Jonas Jelonek [off-list ref] wrote:

A range of managed Realtek-based PoE switches use a small microcontroller
on the PCB to front the actual PSE silicon. The host CPU talks to that
MCU over I2C/SMBus or UART using a fixed 12-byte request/response
protocol with a trailing checksum; the PSE chips are managed by the MCU
and are not accessed directly. Two generations of the protocol exist -
both Realtek's - diverging in opcode numbering and a few response
layouts; the driver handles this with a per-dialect opcode table and
parser hooks for the responses that differ, selected by the compatible.
The specific PSE chip behind the MCU is detected at runtime and only
influences per-chip constants (power scaling and the per-port cap).

This core module implements the protocol, message framing, the dialect
machinery and the pse_controller_ops glue, and exports a registration
helper for transport modules. The I2C and UART transports that drive it
follow in the next patches; the core (PSE_REALTEK_MCU) is selected
automatically by those transports and is not user-selectable on its own.

The realtek-pse-mcu-* files and PSE_REALTEK_MCU* symbols match the
realtek,pse-mcu-* compatibles (see the binding for the naming rationale).
The two protocol generations - gen1 on older Broadcom-PSE boards, gen2 on
Realtek's own PSE silicon - are both Realtek's, handled by the same shared
core, each selecting its dialect via the compatible.

Power budgeting is left to the MCU firmware; the driver advertises
PSE_BUDGET_EVAL_STRAT_DYNAMIC (controller-managed budget) accordingly.

Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>

Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>

Thank you!
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com