Re: [PATCH net v2] amd-xgbe: do not double read link status

[Jakub Kicinski <kuba@kernel.org>]

On Wed, 25 Jun 2025 15:23:15 +0530 Raju Rangoju wrote:
> The link status is latched low so that momentary link drops
> can be detected. Avoid double-reading the status to identify
> short link interruptions, unless the link was already down.

Took me a minute to understand this. How about:

The link status is latched low so that momentary link drops
can be detected. Always double-reading the status defeats this
design feature. Only double read if link was already down.

> -	reg = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_STAT1);
> -	reg = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_STAT1);
> +	if (!pdata->phy.link) {
> +		reg = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_STAT1);
> +		if (reg < 0)
> +			return reg;
> +
> +		if (reg & MDIO_STAT1_LSTATUS)
> +			goto skip_read;
> +	}
>  
> +	reg = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_STAT1);
> +	if (reg < 0)
> +		return reg;
> +skip_read:
>  	if (pdata->en_rx_adap) {
>  		/* if the link is available and adaptation is done,
>  		 * declare link up

Don't use gotos for normal function control flow :/

	reg = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_STAT1);
	if (reg < 0)
		return reg;
	/* Link status is latched low so that momentary link drops
	 * can be detected. If link was already down read again
	 * to get the latest state.
 	 */
	if (!pdata->phy.link && !(reg & MDIO_STAT1_LSTATUS)) {
 		reg = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_STAT1);
		if (reg < 0)
			return reg;
	}

	if (pdata->en_rx_adap) {
 		/* if the link is available and adaptation is done,
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