linux-kernel - Re: [RFC PATCH v2 net-next 03/15] phy: ethernet: add configuration interface for copper backplane Ethernet PHYs

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Message-ID: <20230928133629.GM24230@kernel.org>
Date:   Thu, 28 Sep 2023 15:36:29 +0200
From:   Simon Horman <horms@...nel.org>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Madalin Bucur <madalin.bucur@....com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Camelia Groza <camelia.groza@....com>,
        Li Yang <leoyang.li@....com>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor@...nel.org>,
        Sean Anderson <sean.anderson@...o.com>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>
Subject: Re: [RFC PATCH v2 net-next 03/15] phy: ethernet: add configuration
 interface for copper backplane Ethernet PHYs

On Sat, Sep 23, 2023 at 04:48:52PM +0300, Vladimir Oltean wrote:
> In Layerscape and QorIQ SoCs, compliance with the backplane Ethernet
> protocol is bolted on top of the SerDes lanes using an external IP core,
> that is modeled as an Ethernet PHY. This means that dynamic tuning of
> the electrical equalization parameters of the link needs to be
> communicated with the consumer of the generic PHY.
> 
> Create a small layer of glue API between a networking PHY (dealing with
> the AN/LT logic for backplanes) and a generic PHY by extending the
> phy_configure() API with a new struct phy_configure_opts_ethernet.
> 
> There are 2 directions of interest. In the "local TX training", the
> generic PHY consumer gets requests over the wire from the link partner
> regarding changes we should make to our TX equalization. In the "remote
> TX training" direction, the generic PHY is the producer of requests,
> based on its RX status, and the generic PHY consumer polls for these
> requests until we are happy. Each request is also sent (externally to
> the generic PHY layer) to the link partner board, for it to adjust its
> TX equalization.
> 
> struct phy_configure_opts_ethernet is valid when phy_set_mode_ext() has
> been called with PHY_MODE_ETHERNET or PHY_MODE_ETHTOOL, same as with
> other union phy_configure_opts types.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>

...

> +/**
> + * struct phy_configure_opts_ethernet - Ethernet PHY configuration set

nit: please include documentation of the structure members - type,
local_tx, and remote_tx - here.

> + *
> + * This structure is used to represent the configuration state of an Ethernet
> + * PHY (of various media types).
> + */
> +struct phy_configure_opts_ethernet {
> +	enum ethernet_phy_configure_type type;
> +	union {
> +		struct c72_phy_configure_local_tx local_tx;
> +		struct c72_phy_configure_remote_tx remote_tx;
> +	};
> +};

...