netdev - Re: [net-next] net: ethernet: rtsn: Add support for Renesas Ethernet-TSN

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Message-ID: <20240507111428.GJ720810@ragnatech.se>
Date: Tue, 7 May 2024 13:14:28 +0200
From: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
To: Andrew Lunn <andrew@...n.ch>
Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org
Subject: Re: [net-next] net: ethernet: rtsn: Add support for Renesas
 Ethernet-TSN

On 2024-05-06 21:53:58 +0200, Andrew Lunn wrote:
> On Mon, May 06, 2024 at 04:05:33PM +0200, Niklas Söderlund wrote:
> > Hi Andrew,
> > 
> > Thanks for this explanation, it helps understand what's going on.
> > 
> > On 2024-05-06 03:51:45 +0200, Andrew Lunn wrote:
> > 
> > > What PHY is this? Does it have C22 registers? Can it be identified via
> > > C22 registers 2 and 3?
> > 
> > The PHY in question is mv88q2110 (drivers/net/phy/marvell-88q2xxx.c), 
> > unfortunately I do not have a datasheet for it so I can't tell you much 
> > about it.
> 
> The mv88q2110 declares itself as 0x002b0b20.
> 
> > 
> > <snip>
> > 
> > > 
> > > So i would drop the compatible. See if C22 is sufficient to get the
> > > correct driver loaded.
> > 
> > - Remove C45 compatible; Remove C45 read/write in driver
> > 
> >   The PHY is identified as "Generic PHY", and the correct PHY driver is 
> >   not used. I can't test more than that as the generic PHY driver do not 
> >   implement some quirks I need to get the link up.
> 
> What ID does it return in registers 2 and 3? Anything like 0x002b0b20?
> If there is some usable value there, we can probably extend the driver
> to accept that ID as well.
> 
> Another option it to use a compatible conforming to:
> 
>       - pattern: "^ethernet-phy-id[a-f0-9]{4}\\.[a-f0-9]{4}$"
> 
> ethernet-phy-id002b.0b20
> 
> That will bypass reading ID registers for the ID, and just use the ID
> in the compatible. However, it would be better to read them from the
> PHY.

Thanks for these hints. Using a compatible to indicate which PHY to use 
allows the RTSN driver to not implement C45 read/write functions and 
still operate.

I will look into if I can extend the PHY driver with identification from 
register 2 and 3, but that will be a separate work item.

Unrelated note: I use the ID 0x002b0980 instead of 0x002b0b20 as I have 
a 88Q2110 and not a 88Q2220 PHY, but both are handled by the same PHY
driver.

> 
> 	Andrew
> 
> 

-- 
Kind Regards,
Niklas Söderlund