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Date:   Tue, 31 Oct 2023 07:27:45 +0100
From:   Oleksij Rempel <o.rempel@pengutronix.de>
To:     Vladimir Oltean <olteanv@gmail.com>
Cc:     Ante Knezic <ante.knezic@helmholz.de>, conor+dt@kernel.org,
        UNGLinuxDriver@microchip.com, andrew@lunn.ch, davem@davemloft.net,
        devicetree@vger.kernel.org, edumazet@google.com,
        f.fainelli@gmail.com, krzysztof.kozlowski+dt@linaro.org,
        kuba@kernel.org, linux-kernel@vger.kernel.org, marex@denx.de,
        netdev@vger.kernel.org, pabeni@redhat.com, robh+dt@kernel.org,
        woojung.huh@microchip.com
Subject: Re: [PATCH net-next v4 2/2] net:dsa:microchip: add property to select
Message-ID: <20231031062745.GO3803936@pengutronix.de>
References: <20231024142426.GE3803936@pengutronix.de>
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On Mon, Oct 30, 2023 at 07:42:25PM +0200, Vladimir Oltean wrote:
> On Fri, Oct 27, 2023 at 08:37:43AM +0200, Ante Knezic wrote:
> > On Tue, 24 Oct 2023 16:24:26 +0200, Oleksij Rampel wrote:
> > 
> > > > That is correct, I guess its a matter of nomenclature, but how do you 
> > > > "tell" the switch whether it has REFCLKI routed externally or not if not by 
> > > > setting the 0xC6 bit 3? Is there another way to achieve this?
> > > 
> > > I do not see any other way to "tell" it. The only thing to change in you
> > > patches is a different way to tell it to the kernel.
> > > Instead of introducing a new devicetree property, you need to reuse
> > > phy-mode property.
> > 
> > > ...
> > 
> > > Since phy-mode for RMII was never set correctly, it will most probably
> > > break every single devicetree using KSZ switches. It is the price of fixing
> > > things :/
> > 
> > To Vladimir Oltean: What are your thoughts on this?
> > 
> 
> In addition to all of that, the MAC/PHY roles are not just about the
> direction of the REF_CLK, but also about the /J/ /K/ codewords that are
> placed by the PHY in the inter packet gap on RXD[1:0]. A MAC doesn't do
> this, and if it did, the PHY wouldn't expect it, and AFAIK, would
> blindly propagate those code words onto the BASE-T wire, which is
> undesirable.

Interesting detail. I didn't knew it, it would be good to document
it somewhere near to revrmii binding :)

Regards,
Oleksij
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