linux-kernel - Re: [net-next PATCH] net: phy: aquantia: add AQR111 and AQR111B0 PHY ID

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Date: Tue, 13 Feb 2024 16:10:01 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Christian Marangi <ansuelsmth@...il.com>
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>,
	"Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
	Robert Marko <robimarko@...il.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [net-next PATCH] net: phy: aquantia: add AQR111 and AQR111B0 PHY
 ID

On Tue, Feb 13, 2024 at 03:18:09PM +0100, Christian Marangi wrote:
> On Tue, Feb 13, 2024 at 03:09:57PM +0100, Andrew Lunn wrote:
> > On Tue, Feb 13, 2024 at 02:35:51PM +0100, Christian Marangi wrote:
> > > Add Aquantia AQR111 and AQR111B0 PHY ID. These PHY advertise 10G speed
> > > but actually supports up to 5G speed, hence some manual fixup is needed.
> > 
> > Any chance this is a "golden screwdriver" situation? The chip really
> > can do 10G, but the firmware is supposed to limit it to 5G? This is
> > just a firmware "bug"?
> >
> 
> >From [1] the PHY can support up to 5G so yes it is a firmware bug. I can
> try searching for some regs to fix the wrong provision values if really
> needed.
> 
> [1] https://www.marvell.com/content/dam/marvell/en/public-collateral/transceivers/marvell-phys-transceivers-aqrate-gen3-product-brief-2019-09.pdf

I think you missed the meaning of golden screwdriver.

https://www.urbandictionary.com/define.php?term=Golden%20Screwdriver

It could be that the silicon can do 10G, but marvell are selling it as
a 5G device, with firmware limiting it to 5G. And that firmware
limitation has a bug, so some of the 10G functionality is leaking
through.

Anyway, you change looks O.K.

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew