linux-kernel - Re: [PATCH net-next 3/9] net: phy: add kr phy connection type

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Message-ID: <20200327120151.GG25745@shell.armlinux.org.uk>
Date:   Fri, 27 Mar 2020 12:01:52 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Florinel Iordache <florinel.iordache@....com>, davem@...emloft.net,
        netdev@...r.kernel.org, f.fainelli@...il.com, hkallweit1@...il.com,
        devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
        robh+dt@...nel.org, mark.rutland@....com, kuba@...nel.org,
        corbet@....net, shawnguo@...nel.org, leoyang.li@....com,
        madalin.bucur@....nxp.com, ioana.ciornei@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 3/9] net: phy: add kr phy connection type

On Fri, Mar 27, 2020 at 01:15:15AM +0100, Andrew Lunn wrote:
> On Thu, Mar 26, 2020 at 03:51:16PM +0200, Florinel Iordache wrote:
> > Add support for backplane kr phy connection types currently available
> > (10gbase-kr, 40gbase-kr4) and the required phylink updates (cover all
> > the cases for KR modes which are clause 45 compatible to correctly assign
> > phy_interface and phylink#supported)
> > 
> > Signed-off-by: Florinel Iordache <florinel.iordache@....com>
> > ---
> >  drivers/net/phy/phylink.c | 15 ++++++++++++---
> >  include/linux/phy.h       |  6 +++++-
> >  2 files changed, 17 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
> > index fed0c59..db1bb87 100644
> > --- a/drivers/net/phy/phylink.c
> > +++ b/drivers/net/phy/phylink.c
> > @@ -4,6 +4,7 @@
> >   * technologies such as SFP cages where the PHY is hot-pluggable.
> >   *
> >   * Copyright (C) 2015 Russell King
> > + * Copyright 2020 NXP
> >   */
> >  #include <linux/ethtool.h>
> >  #include <linux/export.h>
> > @@ -303,7 +304,6 @@ static int phylink_parse_mode(struct phylink *pl, struct fwnode_handle *fwnode)
> >  			break;
> >  
> >  		case PHY_INTERFACE_MODE_USXGMII:
> > -		case PHY_INTERFACE_MODE_10GKR:
> 
> We might have a backwards compatibility issue here. If i remember
> correctly, there are some boards out in the wild using
> PHY_INTERFACE_MODE_10GKR not PHY_INTERFACE_MODE_10GBASER.
> 
> See e0f909bc3a242296da9ccff78277f26d4883a79d
> 
> Russell, what do you say about this?

Yes, and that's a point that I made when I introduced 10GBASER to
correct that mistake.  It is way too soon to change this; it will
definitely cause regressions:

$ grep 10gbase-kr arch/*/boot/dts -r
arch/arm64/boot/dts/marvell/cn9131-db.dts:      phy-mode = "10gbase-kr";
arch/arm64/boot/dts/marvell/armada-8040-mcbin.dts:      phy-mode = "10gbase-kr";
arch/arm64/boot/dts/marvell/armada-8040-mcbin.dts:      phy-mode = "10gbase-kr";
arch/arm64/boot/dts/marvell/armada-7040-db.dts:    phy-mode = "10gbase-kr";
arch/arm64/boot/dts/marvell/armada-8040-mcbin-singleshot.dts:   phy-mode = "10gbase-kr";
arch/arm64/boot/dts/marvell/armada-8040-mcbin-singleshot.dts:   phy-mode = "10gbase-kr";
arch/arm64/boot/dts/marvell/armada-8040-clearfog-gt-8k.dts:     phy-mode = "10gbase-kr";
arch/arm64/boot/dts/marvell/armada-8040-db.dts: phy-mode = "10gbase-kr";
arch/arm64/boot/dts/marvell/armada-8040-db.dts: phy-mode = "10gbase-kr";
arch/arm64/boot/dts/marvell/cn9132-db.dts:      phy-mode = "10gbase-kr";
arch/arm64/boot/dts/marvell/cn9130-db.dts:      phy-mode = "10gbase-kr";

So any change to the existing PHY_INTERFACE_MODE_10GKR will likely
break all these platforms.

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