From: Vladimir Oltean <olteanv@gmail.com>
To: Sean Anderson <sean.anderson@seco.com>
Cc: Andrew Lunn <andrew@lunn.ch>,
Heiner Kallweit <hkallweit1@gmail.com>,
Russell King <linux@armlinux.org.uk>,
netdev@vger.kernel.org, Eric Dumazet <edumazet@google.com>,
Tim Harvey <tharvey@gateworks.com>,
"David S . Miller" <davem@davemloft.net>,
linux-kernel@vger.kernel.org, Paolo Abeni <pabeni@redhat.com>,
Jakub Kicinski <kuba@kernel.org>
Subject: Re: [PATCH] phy: aquantia: Configure SERDES mode by default
Date: Fri, 18 Nov 2022 19:30:14 +0200 [thread overview]
Message-ID: <20221118173014.4i7fccrgcqr6dkp4@skbuf> (raw)
In-Reply-To: <1015dfec-542d-8222-6c4e-0cf9d5ee7e5a@seco.com>
On Fri, Nov 18, 2022 at 12:11:30PM -0500, Sean Anderson wrote:
> >> - We can check all the registers to ensure we are actually going to rate
> >> adapt. If we aren't, we tell phylink we don't support it. This is the
> >> least risky, but we can end up not bringing up the link even in
> >> circumstances where we could if we configured things properly. And we
> >> generally know the right way to configure things.
> >
> > Like when?
>
> Well, like whenever the phy says "Please do XFI/2" or some other mode we
> don't have a phy interface mode for. We will never be able to tell the MAC
> "Please do XFI/2" (until we add an interface mode for it), so that's
> obviously wrong.
Add an interface mode for it then... But note that I have absolutely no
clue what XFI/2 is. Apparently Aquantia doesn't want NXP to know....
> >> - Add a configuration option (devicetree? ethtool?) on which option
> >> above to pick. This is probably what we will want to do in the long
> >> term, but I feel like we have enough information to determine the
> >> right thing to do most of the time (without needing manual
> >> intervention).
> >
> > Not sure I see the need, when long-term there is no volunteer to make
> > the Linux driver bring Aquantia PHYs to a known state regardless of
> > vendor provisioning. Until then, there is just no reason to even attempt
> > this.
>
> I mean a config for option 1 vs 2 above.
How would this interact with Marek's proposal for phy-mode to be an
array, and some middle entity (phylink?) selects the SERDES protocol and
rate matching algorithm to use for each medium side link speed?
https://patchwork.kernel.org/project/netdevbpf/cover/20211123164027.15618-1-kabel@kernel.org/
> > Until you look at the procedure in the NXP SDK and see that things are a
> > bit more complicated to get right, like put the PHY in low power mode,
> > sleep for a while. I think a large part of that was determined experimentally,
> > out of laziness to change PHY firmware on some riser cards more than anything.
> > We still expect the production boards to have a good firmware, and Linux
> > to read what that does and adapt accordingly.
>
> Alas, if only Marvell put stuff like this in a manual... All I have is a spec
> sheet and the register reference, and my company has an NDA...
Can't help with much more than providing this hint, sorry. All I can say
is that SERDES protocol override from Linux is possible with care, at
least on some systems. But it may be riddled with landmines.
> We aren't even using this phy on our board, so I am fine disabling rate adaptation
> for funky firmwares.
Disabling rate adaptation is one thing. But there's also the unresolved
XFI/2 issue?
next prev parent reply other threads:[~2022-11-18 17:30 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-14 21:07 [PATCH] phy: aquantia: Configure SERDES mode by default Sean Anderson
2022-11-15 22:37 ` Vladimir Oltean
2022-11-15 22:46 ` Sean Anderson
2022-11-15 23:02 ` Vladimir Oltean
2022-11-17 23:40 ` Sean Anderson
2022-11-18 0:02 ` Andrew Lunn
2022-11-18 17:16 ` Vladimir Oltean
2022-11-18 18:56 ` Andrew Lunn
2022-11-29 0:20 ` Tim Harvey
2022-11-18 16:49 ` Vladimir Oltean
2022-11-18 17:11 ` Sean Anderson
2022-11-18 17:30 ` Vladimir Oltean [this message]
2022-11-18 18:01 ` Sean Anderson
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