linux-kernel - Re: [PATCH net-next 1/2] dt-bindings: net: lan966x: remove PHY reset

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Date:   Tue, 3 May 2022 08:04:23 -0500
From:   Rob Herring <robh+dt@...nel.org>
To:     Michael Walle <michael@...le.cc>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        netdev <netdev@...r.kernel.org>, devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 1/2] dt-bindings: net: lan966x: remove PHY reset

On Thu, Apr 28, 2022 at 6:40 AM Michael Walle <michael@...le.cc> wrote:
>
> The PHY reset was intended to be a phandle for a special PHY reset
> driver for the integrated PHYs as well as any external PHYs. It turns
> out, that the culprit is how the reset of the switch device is done.
> In particular, the switch reset also affects other subsystems like
> the GPIO and the SGPIO block and it happens to be the case that the
> reset lines of the external PHYs are connected to a common GPIO line.
> Thus as soon as the switch issues a reset during probe time, all the
> external PHYs will go into reset because all the GPIO lines will
> switch to input and the pull-down on that signal will take effect.
>
> So even if there was a special PHY reset driver, it (1) won't fix
> the root cause of the problem and (2) it won't fix all the other
> consumers of GPIO lines which will also be reset.
>
> It turns out, the Ocelot SoC has the same weird behavior (or the
> lack of a dedicated switch reset) and there the problem is already
> solved and all the bits and pieces are already there and this PHY
> reset property isn't not needed at all.
>
> There are no users of this binding. Just remove it.

Seems there was 1 user:

/builds/robherring/linux-dt/Documentation/devicetree/bindings/net/microchip,lan966x-switch.example.dtb:
switch@...00000: resets: [[4294967295, 0], [4294967295, 0]] is too
long
 From schema: /builds/robherring/linux-dt/Documentation/devicetree/bindings/net/microchip,lan966x-switch.yaml
/builds/robherring/linux-dt/Documentation/devicetree/bindings/net/microchip,lan966x-switch.example.dtb:
switch@...00000: reset-names: ['switch', 'phy'] is too long
 From schema: /builds/robherring/linux-dt/Documentation/devicetree/bindings/net/microchip,lan966x-switch.yaml

Please fix as this is now failing in linux-next.

Rob