netdev - Re: [PATCH 1/6] net: phy: add interface modes for XFI, SFI

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Date:   Fri, 3 Jan 2020 18:17:19 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     "Madalin Bucur (OSS)" <madalin.bucur@....nxp.com>
Cc:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>
Subject: Re: [PATCH 1/6] net: phy: add interface modes for XFI, SFI

> There are many things pushed down to u-boot so the Linux driver has less
> work to do, that's one of the reasons there is little left there.

I prefer barebox. Which is a problem, since it sounds like Ethernet
will be broken on your boards if i swap to it.

If you are going to offload setting up the hardware, please do it to
firmware. That is independent of the bootloader. The Marvell SoCs do
this for their low level SERDES setup, making SMC calls into the
firmware.

https://patchwork.kernel.org/cover/10880297/

> Ideally this dependency should be removed but then we'd need to make
> a clearer distinction. As you've noticed, currently I don't even
> need to distinguish XFI from SFI because for basic scenarios the
> code does the same thing.  Problem is, if I select a common
> denominator now, and later I need to make this distinction, I'll
> need to update device trees, code, etc. Just like "xgmii" was just
> fine as a placeholder until recently. I'd rather use a correct
> description now.

So it seems like you need two properties. You need a property to tell
your bootloader how to configure the electrical properties of the
SERDES, XFI, SFI, etc.

And you need a property to configure the protocol running over the
SERDES, which is phy-mode.

	Andrew