linux-kernel - Re: [PATCH v2] net: dsa: ksz8795: adjust CPU link to host interface

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Date:   Mon, 7 Dec 2020 20:41:05 +0100
From:   Jean Pihet <jean.pihet@...oldbits.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Ryan Barnett <ryan.barnett@...kwellcollins.com>,
        Conrad Ratschan <conrad.ratschan@...kwellcollins.com>,
        Hugo Cornelis <hugo.cornelis@...ensium.com>,
        Arnout Vandecappelle <arnout.vandecappelle@...ensium.com>
Subject: Re: [PATCH v2] net: dsa: ksz8795: adjust CPU link to host interface

Hi Vladimir,

On Tue, Dec 1, 2020 at 8:48 PM Vladimir Oltean <olteanv@...il.com> wrote:
>
> Hi Jean,
>
> On Tue, Dec 01, 2020 at 07:58:01PM +0100, Jean Pihet wrote:
> > Hi Andrew,
> >
> > On Tue, Dec 1, 2020 at 7:41 PM Andrew Lunn <andrew@...n.ch> wrote:
> > >
> > > On Tue, Dec 01, 2020 at 09:34:08AM +0100, Jean Pihet wrote:
> > > > Add support for RGMII in 100 and 1000 Mbps.
> > > >
> > > > Adjust the CPU port settings from the host interface settings: interface
> > > > MII type, speed, duplex.
> > >
> > > Hi Jean
> > >
> > > You have still not explained why this is needed. Why? is always the
> > > important question to answer in the commit message. The What? is
> > > obvious from reading the patch. Why does you board need this, when no
> > > over board does?
> >
> > I reworked the commit description about the What and thought it was
> > enough. Do you need a cover letter to describe it more?
> >
> > The Why is:
> > "
> > Configure the host port of the switch to match the host interface
> > settings. This is useful when the switch is directly connected to the
> > host MAC interface.
> > "
> > Thank you for reviewing the patch.
>
> First of all, I am not clear if you want the patch merged or not. If you
> do, then I don't understand why you did not use the ./scripts/get_maintainer.pl
> tool to get the email addresses of the people who can help you with
> that. No one from Microchip, not the DSA maintainers, not the networking
> maintainer.
My bad, I thought that sending to both LKML and netdev was enough.

>
> Secondly, don't you get an annoying warning that you should not use
> .adjust_link and should migrate to .phylink_mac_link_up? Why do you
> ignore it? Did you even see it?
No there is no warning using my arm config, both with linux and netdev kernels.

>
> Thirdly, your patch is opaque and has three changes folded into one. You
> refactor some code from ksz8795_port_setup into a separate function, you
> add logic for the speeds of 100 and 10 for RGMII, and you call this
> function from .adjust_link. You must justify why you need all of this,
> and cannot just add 3 lines to ksz8795_port_setup. You must explain that
> the ksz8795_port_setup function does not use information from device
> tree. Then you must explain why the patch is correct.
> The code refactored out of ksz8795_port_setup, plus the changes you've
> added to it, looks now super weird. Half of ksz8795_mii_config treats
> p->phydev.speed as an output variable, and half of it as an input
> variable. To the untrained eye this looks like a hack. I'm sure you can
> clarify. This is what Andrew wants to see.

Ok taking notes here, thanks for the valuable input.

>
> Fourth, seriously now, could you just copy Microchip people to your
> patches? The phylink conversion was done this summer, I'm sure they can
> help with some suggestions.
Ok will do, and check the phylink conversion code.

Thank you for reviewing.

BR,
Jean