netdev - Re: [PATCH] arm64: dts: ls1046ardb: Set aqr106 phy mode to usxgmii

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Date:   Tue, 28 Apr 2020 09:44:48 +0200
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     Madalin Bucur <madalin.bucur@....com>
Cc:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Shawn Guo <shawnguo@...nel.org>, Leo Li <leoyang.li@....com>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "joe.hershberger@...com" <joe.hershberger@...com>,
        "u-boot@...ts.denx.de" <u-boot@...ts.denx.de>
Subject: Re: [PATCH] arm64: dts: ls1046ardb: Set aqr106 phy mode to usxgmii

Hi Madalin,

On Thu, Apr 23, 2020 at 12:59:16PM +0000, Madalin Bucur wrote:
> > -----Original Message-----
> > From: Sascha Hauer <s.hauer@...gutronix.de>
> > Sent: Thursday, April 23, 2020 1:22 PM
> > To: linux-arm-kernel@...ts.infradead.org
> > Cc: Madalin Bucur <madalin.bucur@....com>; Shawn Guo
> > <shawnguo@...nel.org>; Leo Li <leoyang.li@....com>; Sascha Hauer
> > <s.hauer@...gutronix.de>
> > Subject: [PATCH] arm64: dts: ls1046ardb: Set aqr106 phy mode to usxgmii
> > 
> > The AQR107 family of phy devices do not support xgmii, but usxgmii
> > instead. Since ce64c1f77a9d ("net: phy: aquantia: add USXGMII support
> > and warn if XGMII mode is set") the kernel warns about xgmii being
> > used. Change device tree to usxgmii.
> > 
> > Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
> > ---
> >  arch/arm64/boot/dts/freescale/fsl-ls1046a-rdb.dts | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/boot/dts/freescale/fsl-ls1046a-rdb.dts
> > b/arch/arm64/boot/dts/freescale/fsl-ls1046a-rdb.dts
> > index d53ccc56bb63..02fbef92b96a 100644
> > --- a/arch/arm64/boot/dts/freescale/fsl-ls1046a-rdb.dts
> > +++ b/arch/arm64/boot/dts/freescale/fsl-ls1046a-rdb.dts
> > @@ -151,7 +151,7 @@ ethernet@...00 {
> > 
> >  	ethernet@...00 { /* 10GEC1 */
> >  		phy-handle = <&aqr106_phy>;
> > -		phy-connection-type = "xgmii";
> > +		phy-connection-type = "usxgmii";
> >  	};
> > 
> >  	ethernet@...00 { /* 10GEC2 */
> > --
> > 2.26.1
> 
> Hi Sascha,
> 
> thank you for trying to correct this problem. Unfortunately
> "usxgmii" here is incorrect too, as that mode is not supported
> by the LS1046A SoC. The connection mode used, as documented
> by the SoC and PHY datasheets, is XFI. Unfortunately there was
> resistance against including this connection type in the list
> supported by the kernel (please note the distinction between
> connection type and connection mode). At a certain moment the
> two were aliased and the kernel uses connection mode, not
> connection type. While we should describe here the hardware,
> the board connection type (XFI), in the kernel the connection
> mode was lately preferred (10G-BaseR). So, today we cannot use
> "xfi" here, as the hardware description property should read.
> The closest thing we can use is "10gbase-r". Unfortunately, in
> u-boot support for "xfi" is already in place [1] and the device
> tree should be different for the two for this reason - this goes
> against the spirit of the device tree that should not depend on
> the software using it...
> 
> I had on my agenda to fix this problem, had to stop when "xfi"
> was rejected, at the time not even "10gbase-r" was an option.
> Also worth noting here is that, while we change "xgmii" to a
> correct/better value, we should also tolerate the old variant,
> as there are users in the wild unable/unwilling to update the
> device tree and backwards compatibility should be ensured,
> further complicating the matter.

Thanks for the explanation. It looked like one of those simple patch
opportunities at first, apparently it isn't.

Sascha

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