linux-kernel - Re: [PATCH v1] lan743x: correctly handle chips with internal PHY

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Date:   Wed, 4 Nov 2020 11:39:47 -0500
From:   Sven Van Asbroeck <thesven73@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Bryan Whitehead <bryan.whitehead@...rochip.com>,
        David S Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Roelof Berg <rberg@...g-solutions.de>,
        netdev <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] lan743x: correctly handle chips with internal PHY

Hi Andrew, many thanks for looking at this patch !

On Wed, Nov 4, 2020 at 11:27 AM Andrew Lunn <andrew@...n.ch> wrote:
>
> > Note that as a side-effect, the devicetree phy mode now no longer
> > has a default, and always needs to be specified explicitly (via
> > 'phy-connection-type').
>
> That sounds like it could break systems. Why do you do this?

Because the standard mdio library function (of_phy_get_and_connect())
does not appear to support a default value. The original driver
code duplicated that library function's code, with a slight
tweak - the default value.

The default value was introduced quite recently, in the commit which
this patch fixes:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/drivers/net/ethernet/microchip/lan743x_main.c?h=v5.9.3&id=6f197fb63850b26ef8f70f1bfe5900e377910a5a

I'm not sure if other devices that specify phys in devicetrees have a
default for 'phy-connection-type'. I'm wondering if any do?