linux-kernel - Re: [RFC PATCH 3/8] net: pcs: pcs-mtk-lynxi: use 2500Base-X without AN

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Message-ID: <ZU3vrhJe7WmyeVHA@shell.armlinux.org.uk>
Date:   Fri, 10 Nov 2023 08:54:06 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Daniel Golle <daniel@...rotopia.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Felix Fietkau <nbd@....name>, John Crispin <john@...ozen.org>,
        Sean Wang <sean.wang@...iatek.com>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Alexander Couzens <lynxis@...0.eu>,
        Philipp Zabel <p.zabel@...gutronix.de>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-phy@...ts.infradead.org
Subject: Re: [RFC PATCH 3/8] net: pcs: pcs-mtk-lynxi: use 2500Base-X without
 AN

On Thu, Nov 09, 2023 at 09:51:22PM +0000, Daniel Golle wrote:
> Using 2500Base-T SFP modules e.g. on the BananaPi R3 requires manually
> disabling auto-negotiation, e.g. using ethtool. While a proper fix
> using SFP quirks is being discussed upstream, bring a work-around to
> restore user experience to what it was before the switch to the
> dedicated SGMII PCS driver.

No.

> @@ -129,7 +138,8 @@ static int mtk_pcs_lynxi_config(struct phylink_pcs *pcs, unsigned int neg_mode,
>  	if (neg_mode & PHYLINK_PCS_NEG_INBAND)
>  		sgm_mode |= SGMII_REMOTE_FAULT_DIS;
>  
> -	if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED) {
> +	if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED &&
> +	    interface != PHY_INTERFACE_MODE_2500BASEX) {
>  		if (interface == PHY_INTERFACE_MODE_SGMII)
>  			sgm_mode |= SGMII_SPEED_DUPLEX_AN;
>  		bmcr = BMCR_ANENABLE;

Phylink is asking you to have inband enabled. If inband needs to be
disabled, then we need to arrange for phylink to pass
PHYLINK_PCS_NEG_INBAND_DISABLED.

Please don't hack special handling and behaviour into drivers.

Thanks.

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