linux-kernel - [PATCH net-next v4 4/4] net: ftgmac100: Add RGMII delay support for AST2600

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Message-ID:
 <SEYPR06MB5134EBA2235B3D4BE39B19359DCCA@SEYPR06MB5134.apcprd06.prod.outlook.com>
Date: Wed, 12 Nov 2025 03:45:23 +0000
From: Jacky Chou <jacky_chou@...eedtech.com>
To: Andrew Lunn <andrew@...n.ch>
CC: Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Rob Herring
	<robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
	<conor+dt@...nel.org>, Po-Yu Chuang <ratbert@...aday-tech.com>, Joel Stanley
	<joel@....id.au>, Andrew Jeffery <andrew@...econstruct.com.au>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-aspeed@...ts.ozlabs.org"
	<linux-aspeed@...ts.ozlabs.org>, "taoren@...a.com" <taoren@...a.com>
Subject: [PATCH net-next v4 4/4] net: ftgmac100: Add RGMII delay support for
 AST2600

Hi Andrew,

Thank you for your reply.

> > +	/* Add a warning to notify the existed dts based on AST2600. It is
> > +	 * recommended to update the dts to add the rx/tx-internal-delay-ps to
> > +	 * specify the RGMII delay and we recommend using the "rgmii-id" for
> > +	 * phy-mode property to tell the PHY enables TX/RX internal delay and
> > +	 * add the corresponding rx/tx-internal-delay-ps properties.
> > +	 */
> 
> I would not say that exactly. Normally you don't need rx/tx-internal-delay-ps. It
> is only requires for badly designed boards where the designer did not correctly
> balance the line lengths.  So i would word this such that it is recommended to
> use "rgmii-id", and if necessary, add small "rx/tx-internal-delay-ps" values.
> 

Agreed.
I will update this comment in next version.

> > +	scu = syscon_regmap_lookup_by_phandle(np, "aspeed,scu");
> > +	if (IS_ERR(scu)) {
> > +		dev_err(dev, "failed to get aspeed,scu");
> > +		return PTR_ERR(scu);
> > +	}
> 
> This is an optional property. If it does not exist, you have an old DT blob. It is
> not an error. So you need to do different things depending on what the error
> code is. If it does not exist, just return 0 and leave the hardware alone. If it is
> some other error report it, and abort the probe.
> 

Based on this for next version, I want to move the "aspeed,scu" from dtsi to dts.
Change it to optional and accord it whether existed to decide it is old or new DT 
blob.

Thanks,
Jacky