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

[李志 <lizhi2@eswincomputing.com>]

> -----Original Messages-----
> From: "Andrew Lunn" <andrew@lunn.ch>
> Send time:Saturday, 13/06/2026 15:48:46
> To: "Maxime Chevallier" <maxime.chevallier@bootlin.com>
> Cc: lizhi2@eswincomputing.com, devicetree@vger.kernel.org, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, mcoquelin.stm32@gmail.com, alexandre.torgue@foss.st.com, rmk+kernel@armlinux.org.uk, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, linux-riscv@lists.infradead.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, ningyu@eswincomputing.com, linmin@eswincomputing.com, pinkesh.vaghela@einfochips.com, pritesh.patel@einfochips.com, weishangjuan@eswincomputing.com, horms@kernel.org, lee@kernel.org
> Subject: Re: [PATCH net-next v8 3/6] net: stmmac: eic7700: make RGMII delay properties optional
> 
> 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
> 

Thanks for the earlier discussion and for helping clarify the eth0
design.

I'm preparing a v9 of the series. The next revision will address the
issues reported by Sashiko review, mainly DT binding schema and DTS
warnings.

Before I post v9, I'd like to check whether you have any concerns or
suggestions regarding the driver changes.

Thanks,
Zhi