linux-kernel - Re: [PATCH net-next 0/9] XPCS polarity inversion via generic device tree properties

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Message-ID: <aSW--slbJWpXK0nv@makrotopia.org>
Date: Tue, 25 Nov 2025 14:36:42 +0000
From: Daniel Golle <daniel@...rotopia.org>
To: Vladimir Oltean <vladimir.oltean@....com>
Cc: netdev@...r.kernel.org, devicetree@...r.kernel.org,
	linux-phy@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org,
	Horatiu Vultur <horatiu.vultur@...rochip.com>,
	Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Vinod Koul <vkoul@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Eric Woudstra <ericwouds@...il.com>,
	Marek Behún <kabel@...nel.org>,
	Lee Jones <lee@...nel.org>,
	Patrice Chotard <patrice.chotard@...s.st.com>
Subject: Re: [PATCH net-next 0/9] XPCS polarity inversion via generic device
 tree properties

On Sat, Nov 22, 2025 at 09:33:32PM +0200, Vladimir Oltean wrote:
> Polarity inversion (described in patch 3/6) is a feature with at least 3
> potential new users waiting for a generic description:
> - Horatiu Vultur with the lan966x SerDes
> - Daniel Golle with the MaxLinear GSW1xx switches
> - Me with a custom SJA1105 board, switch which uses the DesignWare XPCS
> 
> I became interested in exploring the problem space because I was averse
> to the idea of adding vendor-specific device tree properties to describe
> a common need.

Thank you for coming up with a good solution, and even generalizing
this beyond networking scope :)

> 
> This set contains an implementation of a generic feature that should
> cater to all known needs that were identified during my documentation
> phase. I've added a new user - the XPCS - and I've converted an existing
> user - the EN8811H Ethernet PHY.
> 
> I haven't converted the rest due to various reasons:
> - "mediatek,pnswap" is defined bidirectionally and the underlying
>   SGMII_PN_SWAP_TX_RX register field doesn't make it clear which bit is
>   RX and which is TX. Needs more work and expert knowledge from maintainer.

Just to quickly answer to that one from MediaTek's SDK[1]:
#define SGMII_PN_SWAP_RX               BIT(1)
#define SGMII_PN_SWAP_TX               BIT(0)

So MediaTek LynxI is ready to be supported via the standard properties
you are suggesting.

[1]: https://git01.mediatek.com/plugins/gitiles/openwrt/feeds/mtk-openwrt-feeds/+/5cecec123e1ab4c7f4eabd5630e8e8b2e89b9cf0/autobuild/unified/filogic/master/files/target/linux/mediatek/patches-6.6/999-2607-net-pcs-mtk-lynxi-add-individual-polarity-control.patch


> - "st,px_rx_pol_inv" - its binding is a .txt file and I don't have time
>   for such a large detour to convert it to dtschema.
> - "st,pcie-tx-pol-inv" and "st,sata-tx-pol-inv" - these are defined in a
>   .txt schema but are not implemented in any driver. My verdict would be
>   "delete the properties" but again, I would prefer not introducing such
>   dependency to this series.
> 
> Vladimir Oltean (9):
>   dt-bindings: phy: rename transmit-amplitude.yaml to
>     phy-common-props.yaml
>   dt-bindings: phy-common-props: create a reusable "protocol-names"
>     definition
>   dt-bindings: phy-common-props: RX and TX lane polarity inversion
>   dt-bindings: net: xpcs: allow properties from phy-common-props.yaml
>   phy: add phy_get_rx_polarity() and phy_get_tx_polarity()
>   net: pcs: xpcs: promote SJA1105 TX polarity inversion to core
>   net: pcs: xpcs: allow lane polarity inversion
>   net: phy: air_en8811h: deprecate "airoha,pnswap-rx" and
>     "airoha,pnswap-tx"
>   dt-bindings: net: airoha,en8811h: deprecate "airoha,pnswap-rx" and
>     "airoha,pnswap-tx"
> 
>  .../bindings/net/airoha,en8811h.yaml          |  11 +-
>  .../bindings/net/pcs/snps,dw-xpcs.yaml        |   5 +-
>  .../bindings/phy/phy-common-props.yaml        | 152 ++++++++++++++++++
>  .../bindings/phy/transmit-amplitude.yaml      | 103 ------------
>  MAINTAINERS                                   |  21 +++
>  drivers/net/pcs/Kconfig                       |   1 +
>  drivers/net/pcs/pcs-xpcs-nxp.c                |  11 --
>  drivers/net/pcs/pcs-xpcs.c                    |  58 ++++++-
>  drivers/net/pcs/pcs-xpcs.h                    |   2 +-
>  drivers/net/phy/Kconfig                       |   1 +
>  drivers/net/phy/air_en8811h.c                 |  50 ++++--
>  drivers/phy/Kconfig                           |   9 ++
>  drivers/phy/Makefile                          |   1 +
>  drivers/phy/phy-common-props.c                | 117 ++++++++++++++
>  include/dt-bindings/phy/phy.h                 |   4 +
>  include/linux/phy/phy-common-props.h          |  20 +++
>  16 files changed, 426 insertions(+), 140 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/phy/phy-common-props.yaml
>  delete mode 100644 Documentation/devicetree/bindings/phy/transmit-amplitude.yaml
>  create mode 100644 drivers/phy/phy-common-props.c
>  create mode 100644 include/linux/phy/phy-common-props.h
> 
> -- 
> 2.34.1
>