linux-kernel - Re: [PATCH v2 5/5] arm64: dts: ti: Add TQ-Systems TQMa62xx SoM and MBa62xx carrier board Device Trees

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Message-ID: <c902a56cf34838f60cee67624bb923e91d74e9e0.camel@ew.tq-group.com>
Date: Mon, 09 Dec 2024 14:55:31 +0100
From: Matthias Schiffer <matthias.schiffer@...tq-group.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Nishanth Menon <nm@...com>, Vignesh Raghavendra <vigneshr@...com>, Tero
 Kristo <kristo@...nel.org>, Rob Herring <robh@...nel.org>, Krzysztof
 Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Greg
 Kroah-Hartman <gregkh@...uxfoundation.org>, Kees Cook <kees@...nel.org>,
 Tony Luck <tony.luck@...el.com>, "Guilherme G. Piccoli"
 <gpiccoli@...lia.com>, Felipe Balbi <balbi@...nel.org>,
 linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org, 
 linux-hardening@...r.kernel.org, Devarsh Thakkar <devarsht@...com>, Hari
 Nagalla <hnagalla@...com>, linux@...tq-group.com
Subject: Re: [PATCH v2 5/5] arm64: dts: ti: Add TQ-Systems TQMa62xx SoM and
 MBa62xx carrier board Device Trees

On Mon, 2024-12-09 at 14:24 +0100, Andrew Lunn wrote:
> 
> > +&cpsw_port1 {
> > +	phy-mode = "rgmii-rxid";
> > +	phy-handle = <&cpsw3g_phy0>;
> > +};
> > +
> > +&cpsw_port2 {
> > +	phy-mode = "rgmii-rxid";
> > +	phy-handle = <&cpsw3g_phy3>;
> > +};
> 
> rgmii-rxid is very odd.
> 
> > +
> > +&cpsw3g_mdio {
> > +	status = "okay";
> > +	pinctrl-names = "default";
> > +	pinctrl-0 = <&main_mdio1_pins>;
> > +
> > +	cpsw3g_phy0: ethernet-phy@0 {
> > +		compatible = "ethernet-phy-ieee802.3-c22";
> > +		reg = <0x0>;
> > +		reset-gpios = <&main_gpio1 11 GPIO_ACTIVE_LOW>;
> > +		reset-assert-us = <1000>;
> > +		reset-deassert-us = <1000>;
> > +		ti,rx-internal-delay = <DP83867_RGMIIDCTL_2_00_NS>;
> 
> I guess this is the explanation.
> 
> What happens when you use rgmii-id, and don't have this delay here?
> That would be normal.
> 
> 	Andrew

This is normal for AM62-based boards, see the DTSI of the TI reference
starterkit for example:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi#n451

With rgmii-id, both ti,rx-internal-delay and ti,tx-internal-delay should be set.
As ti,*-internal-delay sets the delay on the PHY side, phy-mode "rgmii" is the
one that would not use either:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/net/ti,dp83867.yaml#n78

At the end of the day, does it really matter as long as MAC and PHY agree on the
used mode? We copied this part of the hardware design from the TI reference
board, and did our hardware qualification with these settings, so I think it
makes sense to use the same phy-mode configuration.

Best regards,
Matthias

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