linux-kernel - Re: [net-next RFC PATCH 0/2] net: phy: aquantia: fix system interface provision

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Date: Tue, 13 Feb 2024 22:03:05 +0100
From: Christian Marangi <ansuelsmth@...il.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Robert Marko <robimarko@...il.com>,
	"Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [net-next RFC PATCH 0/2] net: phy: aquantia: fix system
 interface provision

On Tue, Feb 13, 2024 at 09:58:59PM +0100, Andrew Lunn wrote:
> > > So in effect, the driver needs to write every single register it
> > > depends on.
> > >
> > 
> > Well if that's the case then this RFC patch is a must. With a
> > misconfigured System Interface configuration, the PHY can't comunicate
> > with the MAC.
> > 
> > > > This might be the safest change but again would not give us 100% idea that
> > > > the thing provision by the FW are correct.
> > > 
> > > I would say, we have to assume provision is 100% wrong. Write every
> > > single register with the needed value.
> > > 
> > > Is the provisioning information available? Can it be read from the
> > > flash? Can it be dumped from firmware we have on disk? Dumping it for
> > > a number of devices could give a list of register values which are
> > > highly suspect, ones that OEMs typically mess with. We could start by
> > > always setting those registers.
> > >
> > 
> > We know where they are stored in the FW but it's not documented how the
> > provision values are stored in the FW. (the format, how they are
> > organized...) I can waste some time trying to reverse it and produce a
> > tool to parse them if needed.
> 
> It might be worth it. How complex could it be? The obvious format is a
> C45 mmd.reg pair and a value.
>

Working on it. I already confirmed the FW have actually a provision part
and is not empty.

The format looks to be u16 reg 16 value but I need to understand it
better as not everything about provision is in mmd 1e so there must be
some magic values to signal where the section has to be appled.

> > Would love also some comments by Russell about this, there was a patch
> > adding support for WoL where another user was messing with these regs
> > and he was with the idea of being careful with overwriting the provision
> > values.
> 
> I expect the SERDES eye configuration is in there somewhere, and we
> should not touch that. That was one of the arguments Aquantia made at
> the time, that needs to be stored somewhere, and is board specific.
> 
> But knowing what standard 802.3 registers are commonly changed would
> be useful, and could help track down silly problems like the
> transmitter being disabled by default by provisioning.
>

Yes having a tool to parse them would probably be useful and eventually
even apply fixup in the firmware loading (if we really want)

-- 
	Ansuel