netdev - Re: [PATCH net-next 6/9] net: phy: add backplane kr driver support

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Message-ID: <20200401141113.GC62290@lunn.ch>
Date:   Wed, 1 Apr 2020 16:11:13 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Florinel Iordache <florinel.iordache@....com>
Cc:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "corbet@....net" <corbet@....net>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        Leo Li <leoyang.li@....com>,
        "Madalin Bucur (OSS)" <madalin.bucur@....nxp.com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 6/9] net: phy: add backplane kr driver support

> > > +     val = phy_read_mmd(bpphy, MDIO_MMD_AN, bp_phy-
> > >bp_dev.mdio.an_status);
> > > +     val = phy_read_mmd(bpphy, MDIO_MMD_AN,
> > > + bp_phy->bp_dev.mdio.an_status);
> > 
> > Why not just
> > 
> > val = phy_read_mmd(bpphy, MDIO_MMD_AN, MDIO_CTRL1);
> > 
> > Or is your hardware not actually conformant to the standard?
> > 
> > There has also been a lot of discussion of reading the status twice is correct or
> > not. Don't you care the link has briefly gone down and up again?
> > 
> >         Andrew
> 
> This could be changed to use directly the MDIO_STAT1 in order to read
> AN status (and use MDIO_CTRL1 for writing the control register) but this
> is more flexible and more readable

Less readale. MDIO_STAT1 is well known. What does
bp_dev.mdio.an_status mean?

In general, core code should be KISS, and assume everything follows
the standard. We don't want to scatter workarounds for non-conformant
hardware in core code. Such workarounds should be in the drivers where
they are hidden away.

> + bpkr->mdio.an_control = MDIO_CTRL1;
> + bpkr->mdio.an_status = MDIO_STAT1;
> + bpkr->mdio.an_ad_ability_0 = MDIO_PMA_EXTABLE_10GBKR;
> + bpkr->mdio.an_ad_ability_1 = MDIO_PMA_EXTABLE_10GBKR + 1;
> + bpkr->mdio.an_lp_base_page_ability_1 = MDIO_PMA_EXTABLE_10GBKR + 4;

Please drop this, and use the #defines directly.

       Andrew