Re: [PATCH net-next v8 3/6] net: stmmac: eic7700: make RGMII delay properties optional

[Andrew Lunn <andrew@lunn.ch>]

On Wed, Jun 10, 2026 at 10:26:50AM +0200, Maxime Chevallier wrote:
> Hi,
> 
> On 6/10/26 03:29, lizhi2@eswincomputing.com wrote:
> > From: Zhi Li <lizhi2@eswincomputing.com>
> > 
> > Make rx-internal-delay-ps and tx-internal-delay-ps optional in the
> > EIC7700 DWMAC driver.
> > 
> > The driver previously required both properties to be present and would
> > fail probe when they were missing. This restricts valid hardware
> > configurations where RGMII timing is instead provided by the PHY or
> > board design.
> > 
> > Update the driver to treat missing delay properties as zero delay,
> > allowing systems without explicit MAC-side delay tuning to operate
> > correctly.
> > 
> > This aligns the driver behavior with the updated device tree binding
> > and provides a safe default configuration when MAC-side delay
> > programming is not required.
> > 
> > Signed-off-by: Zhi Li <lizhi2@eswincomputing.com>
> > ---
> >  drivers/net/ethernet/stmicro/stmmac/dwmac-eic7700.c | 6 ------
> >  1 file changed, 6 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-eic7700.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-eic7700.c
> > index 4ac979d874d6..ec99b597aeaf 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-eic7700.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-eic7700.c
> > @@ -165,9 +165,6 @@ static int eic7700_dwmac_probe(struct platform_device *pdev)
> >  		dwc_priv->eth_clk_dly_param &= ~EIC7700_ETH_RX_ADJ_DELAY;
> >  		dwc_priv->eth_clk_dly_param |=
> >  				 FIELD_PREP(EIC7700_ETH_RX_ADJ_DELAY, val);
> > -	} else {
> > -		return dev_err_probe(&pdev->dev, -EINVAL,
> > -			"missing required property rx-internal-delay-ps\n");
> >  	}
> >  
> >  	/* Read tx-internal-delay-ps and update tx_clk delay */
> > @@ -187,9 +184,6 @@ static int eic7700_dwmac_probe(struct platform_device *pdev)
> >  		dwc_priv->eth_clk_dly_param &= ~EIC7700_ETH_TX_ADJ_DELAY;
> >  		dwc_priv->eth_clk_dly_param |=
> >  				 FIELD_PREP(EIC7700_ETH_TX_ADJ_DELAY, val);
> > -	} else {
> > -		return dev_err_probe(&pdev->dev, -EINVAL,
> > -			"missing required property tx-internal-delay-ps\n");
> >  	}
> 
> I think then you need to handle RGMII, RGMII_ID, RGMII_RXID and RGMII_TXID,
> by using default delays for these (usually around 2ns), as here all delays
> will be set to 0, regardless of the RGMII mode in use.

No. By default, the MAC adds 0ns delay, and passes the phy-mode to the
PHY. It will then add the 2ns delay. It is possible to use the
tx-internal-delay-ps and rx-internal-delay-ps in the MAC to add small
tuning delays, but not the full 2ns.

https://elixir.bootlin.com/linux/v6.15/source/Documentation/devicetree/bindings/net/ethernet-controller.yaml#L287

	Andrew