linux-kernel - Re: [PATCH 5/8] net: ethernet: ti: am65-cpsw: Add support for fixed-link configuration

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Date:   Wed, 14 Sep 2022 17:09:30 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Siddharth Vadapalli <s-vadapalli@...com>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, robh+dt@...nel.org,
        krzysztof.kozlowski@...aro.org, krzysztof.kozlowski+dt@...aro.org,
        vladimir.oltean@....com, grygorii.strashko@...com, vigneshr@...com,
        nsekhar@...com, netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kishon@...com
Subject: Re: [PATCH 5/8] net: ethernet: ti: am65-cpsw: Add support for
 fixed-link configuration

On Wed, Sep 14, 2022 at 03:20:50PM +0530, Siddharth Vadapalli wrote:
> Check for fixed-link in am65_cpsw_nuss_mac_config() using struct
> am65_cpsw_slave_data's phy_node property to obtain fwnode. Since
> am65_cpsw_nuss_mac_link_up() is not invoked in fixed-link mode, perform
> the relevant operations in am65_cpsw_nuss_mac_config() itself.

Further to my other comments, you also fail to explain that, when in
fixed-link SGMII mode, you _emulate_ being a PHY - which I deduce
since you are sending the duplex setting and speed settings via the
SGMII control word. Also, as SGMII was invented for a PHY to be able
to communicate the media negotiation resolution to the MAC, SGMII
defines that the PHY fills in the speed and duplex information in
the control word to pass it to the MAC, and the MAC acknowledges this
information. There is no need (and SGMII doesn't permit) the MAC to
advertise what it's doing.

Maybe this needs to be explained in the commit message?

This doesn't have any bearing on the other comments I've made.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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