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Date: Wed, 8 May 2024 17:21:11 +0100
From: Daniel Golle <daniel@makrotopia.org>
To: Andrew Lunn <andrew@lunn.ch>
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Subject: Re: [PATCH 3/3] net: phy: mediatek: add support for built-in 2.5G
 ethernet PHY on MT7988
Message-ID: <Zjumd3bnZDu9LYGH@makrotopia.org>
References: <20240425023325.15586-1-SkyLake.Huang@mediatek.com>
 <20240425023325.15586-4-SkyLake.Huang@mediatek.com>
 <ZiocBmBWiNnbeyGq@shell.armlinux.org.uk>
 <4ccd437ee744382a8483ffe71d06cd495dacec71.camel@mediatek.com>
 <577176af-9f6c-45f9-824f-2b4ca762b2f7@lunn.ch>
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In-Reply-To: <577176af-9f6c-45f9-824f-2b4ca762b2f7@lunn.ch>

On Wed, May 08, 2024 at 02:30:21PM +0200, Andrew Lunn wrote:
> > I'm not sure I really get this. MT7988's internal 2.5Gphy is built
> > inside SoC. We won't have a number of these PHYs.
> 
> How long does firmware download take? If you are holding RTNL you are
> blocking all other network configuration. How many Ethernets does this
> device have? If it is just one, it is not too bad, but if there is a
> built in switch, you cannot be configuring that switch at the same
> time firmware download is happening...

The MT7988 SoC has a bunch of network interfaces:

 - GMAC0 is typically connected as conduit to a 4-port MT7530-like DSA
   switch offering 4 1GE user ports. PHY driver mediatek-ge-soc.c takes
   care of those, and yes, they do need some "care"...

 - GMAC1 can be used with the internal 2.5GE PHY (ie. with the driver
   discussed here) OR for to connect an external PHY or SFP via
   1000Base-X, 2500Base-X, SGMII, 5GBase-R, 10GBase-R or USXGMII.

 - GMAC2 is can only be used with an external PHY or SFP using
   1000Base-X, 2500Base-X, SGMII, 5GBase-R, 10GBase-R or USXGMII.

So while there is only exactly one of the internal 2.5GE PHY there are
many other network interfaces on that same SoC.

I hope that clarifies things a bit.