linux-kernel - Re: [PATCH net-next v4 2/2] net:dsa:microchip: add property to select

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Message-ID: <20231031062745.GO3803936@pengutronix.de>
Date:   Tue, 31 Oct 2023 07:27:45 +0100
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Ante Knezic <ante.knezic@...mholz.de>, conor+dt@...nel.org,
        UNGLinuxDriver@...rochip.com, andrew@...n.ch, davem@...emloft.net,
        devicetree@...r.kernel.org, edumazet@...gle.com,
        f.fainelli@...il.com, krzysztof.kozlowski+dt@...aro.org,
        kuba@...nel.org, linux-kernel@...r.kernel.org, marex@...x.de,
        netdev@...r.kernel.org, pabeni@...hat.com, robh+dt@...nel.org,
        woojung.huh@...rochip.com
Subject: Re: [PATCH net-next v4 2/2] net:dsa:microchip: add property to select

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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