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

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Message-ID: <20231023082230.17772-1-ante.knezic@helmholz.de>
Date:   Mon, 23 Oct 2023 10:22:30 +0200
From:   Ante Knezic <ante.knezic@...mholz.de>
To:     <o.rempel@...gutronix.de>
CC:     <UNGLinuxDriver@...rochip.com>, <andrew@...n.ch>,
        <ante.knezic@...mholz.de>, <conor+dt@...nel.org>,
        <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>, <olteanv@...il.com>, <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, 23 Oct 2023 09:58:48 +0200, Oleksij Rempel wrote:

> If I see it correctly, KSZ9897R supports RMII on two ports (6 and 7)
> with configurable clock direction. See page 124 "5.2.3.2 XMII Port Control 1
> Register"
> http://ww1.microchip.com/downloads/en/DeviceDoc/00002330B.pdf

Clock direction is possible I guess with other devices as well, but I don't see
this specific property (routing REFCLKO to REFCLKI internally when switch is
used as clock provider) for any other, including KSZ9897? 
I am no expert on micrel switches, but this to me looks like something specific
only to KSZ88X3 devices as the clocking seems a bit different on KSZ9897 and
alike. KSZ88X3 may generate clock to REFCLKO but still needs this clock fed
back to REFCLKI (or will be routed internally with the "microchip-rmii-internal"
property). This is managed differently on KSZ9897?