netdev - Re: [PATCH RFC net-next] net: phy: marvell10g: add downshift tunable support

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Date:   Tue, 20 Jul 2021 18:39:41 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Marek Behún <kabel@...nel.org>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH RFC net-next] net: phy: marvell10g: add downshift tunable
 support

On Tue, Jul 20, 2021 at 07:32:23PM +0200, Marek Behún wrote:
> On Tue, 20 Jul 2021 18:14:01 +0100
> "Russell King (Oracle)" <linux@...linux.org.uk> wrote:
> 
> > On Tue, Jul 20, 2021 at 05:04:24PM +0200, Marek Behún wrote:
> > > Hi Russell,
> > > 
> > > On Tue, 20 Jul 2021 14:38:20 +0100
> > > Russell King <rmk+kernel@...linux.org.uk> wrote:
> > >   
> > > > Add support for the downshift tunable for the Marvell 88x3310 PHY.
> > > > Downshift is only usable with firmware 0.3.5.0 and later.  
> > > 
> > > mv3310_{g,s}et_features are also used for 88E211x, but there is no
> > > such register in the documentation for these PHYs. (Also firmware
> > > versions on those are different, the newest is 8.3.0.0, but thats
> > > not important.) My solution would be to rename the current methods
> > > prefix to mv211x_ and and add new mv3310_{g,s}et_tunable methods.  
> > 
> > There's more than just the tunables themselves - there's also
> > config_init().
> > 
> > We already need to reject downshift when old firmware is running,
> > as that fails to work correctly. So, we can just do that for
> > 88E211x as well, adding a flag to struct mv3310_chip to indicate
> > whether downshift is present. Sound sensible?
> 
> Hmm, maybe add the flag to struct mv3310_priv, instead of struct
> mv3310_chip, since the latter is static. And fill in the flag in
> mv3310_probe() function, depending on firmware version?

I was intending to leave the firmware version check where it was and
just add a flag to say "this has downshift". The older firmwares on
3310 are basically buggy - they do downshift but only from 1G to 100M,
they fail to go to 10M.

> BTW would you agree with a patch renaming the mv3310_ prefixes to
> mv10g_ for all functions that are generic to both mv3310_ and mv2110_?
> I was thinking about such a thing because it has become rather
> confusing.

I've been thinking the same thing actually.

-- 
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