netdev - Re: [PATCH net-next] net: pcs: tse: port to pcs-lynx

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Date:   Tue, 21 Feb 2023 08:34:12 +0100
From:   Maxime Chevallier <maxime.chevallier@...tlin.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Vladimir Oltean <vladimir.oltean@....com>, davem@...emloft.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        thomas.petazzoni@...tlin.com, Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org,
        Ioana Ciornei <ioana.ciornei@....com>
Subject: Re: [PATCH net-next] net: pcs: tse: port to pcs-lynx

Hi Vlad, Andrew,

On Fri, 10 Feb 2023 21:02:39 +0100
Andrew Lunn <andrew@...n.ch> wrote:

> On Fri, Feb 10, 2023 at 09:31:59PM +0200, Vladimir Oltean wrote:
> > On Fri, Feb 10, 2023 at 08:09:49PM +0100, Maxime Chevallier wrote:  
> > > When submitting the initial driver for the Altera TSE PCS,
> > > Russell King noted that the register layout for the TSE PCS is
> > > very similar to the Lynx PCS. The main difference being that TSE
> > > PCS's register space is memory-mapped, whereas Lynx's is exposed
> > > over MDIO.
> > > 
> > > Convert the TSE PCS to reuse the whole logic from Lynx, by
> > > allowing the creation of a dummy MDIO bus, and a dummy MDIO
> > > device located at address 0 on that bus. The MAC driver that uses
> > > this PCS must provide callbacks to read/write the MMIO.
> > > 
> > > Also convert the Altera TSE MAC driver to this new way of using
> > > the TSE PCS.
> > > 
> > > Signed-off-by: Maxime Chevallier <maxime.chevallier@...tlin.com>
> > > ---
> > >  drivers/net/ethernet/altera/altera_tse.h      |   2 +-
> > >  drivers/net/ethernet/altera/altera_tse_main.c |  50 ++++-
> > >  drivers/net/pcs/Kconfig                       |   4 +
> > >  drivers/net/pcs/pcs-altera-tse.c              | 194
> > > +++++++----------- include/linux/pcs-altera-tse.h
> > > |  22 +- 5 files changed, 142 insertions(+), 130 deletions(-)  
> > 
> > The glue layer is larger than the duplicated PCS code? :(  
> 
> I was wondering if the glue could actually be made generic. The kernel
> has a number of reasonably generic MMIO device drivers, which are just
> given an address range and assume a logical mapping.
> 
> Could this be made into a generic MDIO MMIO bus driver, which just
> gets configured with a base address, and maybe a stride between
> registers?

That would be ideal, I'll spin a new series prorotyping this, indeed
that can be interesting for other devices.

Thanks for the review,

Maxime

> 	Andrew