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

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Message-ID: <20231023075848.GA3786047@pengutronix.de>
Date:   Mon, 23 Oct 2023 09:58:48 +0200
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Ante Knezic <ante.knezic@...mholz.de>
Cc:     olteanv@...il.com, UNGLinuxDriver@...rochip.com, andrew@...n.ch,
        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, 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 23, 2023 at 09:27:00AM +0200, Ante Knezic wrote:
> On Fri, 20 Oct 2023 17:37:59 +0300, Vladimir Oltean wrote:
> 
> > Sorry, I didn't realize on v3 that you didn't completely apply my
> > feedback on v2. Can "microchip,rmii-clk-internal" be a port device tree
> > property? You have indeed moved its parsing to port code, but it is
> > still located directly under the switch node in the device tree.
> > 
> > I'm thinking that if this property was also applicable to other switches
> > with multiple RMII ports, the setting would be per port rather than global.
> 
> As far as I am aware only the KSZ8863 and KSZ8873 have this property available,
> but the biggger issue might be in scaling this to port property as the register
> "Forward Invalid VID Frame and Host Mode" where the setting is applied is
> located under "Advanced Control Registers" section which is actually global at
> least looking from the switch point of view. Usually port properties are more
> applicable when registers in question are located under "Port Registers" section.
> This is somewhat similar to for example enabling the tail tag mode which is 
> again used only by the port 3 interface and is control from "Global Control 1"
> register.
> With this in mind - if you still believe we should move this to port dt 
> property, then should we forbid setting the property for any other port other 
> than port 3, and can/should this be enforced by the dt schema?
> 

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

Regards,
Oleksij
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