linux-kernel - 回覆: [net-next 4/4] net: ftgmac100: add RGMII delay for AST2600

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Message-ID:
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Date: Tue, 18 Mar 2025 10:46:58 +0000
From: Jacky Chou <jacky_chou@...eedtech.com>
To: Andrew Lunn <andrew@...n.ch>
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Subject:
 回覆: [net-next 4/4] net: ftgmac100: add RGMII delay for AST2600

Hi Andrew,

Thank you for your reply.

> > +	u32 rgmii_tx_delay, rgmii_rx_delay;
> > +	u32 dly_reg, tx_dly_mask, rx_dly_mask;
> > +	int tx, rx;
> > +
> > +	netdev = platform_get_drvdata(pdev);
> > +	priv = netdev_priv(netdev);
> > +
> > +	tx = of_property_read_u32(np, "tx-internal-delay-ps", &rgmii_tx_delay);
> > +	rx = of_property_read_u32(np, "rx-internal-delay-ps",
> > +&rgmii_rx_delay);
> 
> > +	if (!tx) {
> 
> The documentation for of_property_read_u32() says:
> 
>  * Return: 0 on success, -EINVAL if the property does not exist,
>  * -ENODATA if property does not have a value, and -EOVERFLOW if the
>  * property data isn't large enough.
> 
> You need to handle EINVAL different to the other errors, which are real errors
> and should fail the probe.
> 
> The commit message, and probably the binding needs to document what
> happens when the properties are not in the DT blob. This needs to be part of
> the bigger picture of how you are going to sort out the mess with existing .dts
> files listing 'rgmii' when in fact they should be 'rgmii-id'.

Why can't the MAC add internal delay to RGMII? Is it necessary to add on PHY side?

> 
> > +		/* Use tx-internal-delay-ps as index to configure tx delay
> > +		 * into scu register.
> > +		 */
> > +		if (rgmii_tx_delay > 64)
> > +			dev_warn(&pdev->dev, "Get invalid tx delay value");
> 
> Return EINVAL and fail the probe.

Agreed.
I just show warning here, because sometimes the RGMII delay value will configure at bootloader.
Therefore, it shows message and ignore the delay value when it got wrong.

I will add check for this in next version.

Thanks,
Jacky