linux-kernel - Re: PHY issue with SJA1105Q/DP84849I Design

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Message-ID: <20231230112806.o5ia43mu4mo64lea@skbuf>
Date: Sat, 30 Dec 2023 13:28:06 +0200
From: Vladimir Oltean <olteanv@...il.com>
To: Jagan Teki <jagan@...rulasolutions.com>
Cc: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>,
	"Andrew F. Davis" <afd@...com>,
	Florian Fainelli <f.fainelli@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org,
	Michael Nazzareno Trimarchi <michael@...rulasolutions.com>,
	Ioana Ciornei <ioana.ciornei@....com>,
	Shawn Guo <shawnguo@...nel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	Fabio Estevam <festevam@...il.com>
Subject: Re: PHY issue with SJA1105Q/DP84849I Design

On Sat, Dec 30, 2023 at 01:48:38AM +0530, Jagan Teki wrote:
> On Fri, Dec 29, 2023 at 8:55 PM Vladimir Oltean <olteanv@...il.com> wrote:
> > Why all these combinations? You don't know which switch port is which?
> 
> This is where I get confused in the first place. I didn't find proper
> information on binding about how the physical pin-out is to be
> configured in DT ports or maybe I didn't understand properly.
> 
> As per schematics.
> Pin MII0_RXD0-D3/TXD0-D3 is connected to PROC_MII0_RXD0-D3/TXD0-D3
> this would be fec0.
> Pin MII1_RXD0-D3/TXD0-D3 is connected to PHY_MII1_RXD0-D3/TXD0-D3 this
> would be ethphy0.
> Pin MII2_RXD0-D3/TXD0-D3 is connected to PHY_MII2_RXD0-D3/TXD0-D3 this
> would be ethphy1.
> Pin MII3_RXD0-D3/TXD0-D3 is grounded
> Pin MII4_RXD0-D3/TXD0-D3 is grounded
> 
> So, I did use the above 3 combinations and assumed fec0 is always a
> port4 based on existing DTS in the tree. Please let me know which
> configuration is proper as per schematic connections.

With this switch, any port can be a CPU port. The CPU port selection
from existing, unrelated upstream boards has no influence upon yours.

The pin naming in "MII0_RXD/TXD" follows the same numbering scheme as
"port@0" etc. The SJA1105PQRS.pdf datasheet should tell you as much.
So your CPU port should be the "port@0" node and not "port@4". The
switch "port@3" and "port@4" sound like they should be the ones with
status = "disabled".

> > If you are truly using MII, then you should remove the RGMII delay
> > properties, and since you are using a 6.1 kernel - hence after kernel
> > commit 5d645df99ac6 ("net: dsa: sja1105: determine PHY/MAC role from PHY
> > interface type") - you should be using phy-mode = "rev-mii" to put this
> > port in MII PHY ("RevMII") mode - to interoperate with the FEC in MII
> > MAC mode.
> 
> Okay, I will remove RGMII delay. is phy-mode = "rev-mii" applicable to
> all ports or only for fec port4?

Use phy-mode = "rev-mii" for the switch port going to the FEC, and
phy-mode = "mii" for the switch ports going to MII PHYs (and for the FEC
itself).

> > You can also use the RX counters to determine which switch port is which
> > (but the phy-handle of each port to each PHY needs to be correct).
> 
> RX counters in ethtool you mean?

Yes.