[PATCH 1/2] net: phy: micrel_ksz90x1: disable asymmetric pause for KSZ9031

[Quentin Schulz]

Hi Max, Markus,

On 11/21/25 9:18 AM, Max Merchel wrote:
> From: Markus Niebel <Markus.Niebel at ew.tq-group.com>
> 
> Disable the support due to chip errata and call genphy_config_aneg
> instead of genphy_config. For a complete describtion look at the
> errata sheets: DS80000691D or DS80000692D.
> 

Linux counterpart seems to be 3aed3e2a143c ("net: phy: micrel: add Asym 
Pause workaround"). It does seem to set an additional bit 
(ADVERTISE_PAUSE_CAP in U-Boot) but the explanation doesn't seem to 
apply to U-Boot.

Though another interesting commit is in the Linux tree as well, 
407d8098cb1a ("net: phy: micrel: add Asym Pause workaround for 
KSZ9021"). I assume we need a similar fix in ksz9021_config()?

> Signed-off-by: Markus Niebel <Markus.Niebel at ew.tq-group.com>
> Signed-off-by: Max Merchel <Max.Merchel at ew.tq-group.com>
> ---
>   drivers/net/phy/micrel_ksz90x1.c | 18 +++++++++++++++++-
>   1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/phy/micrel_ksz90x1.c b/drivers/net/phy/micrel_ksz90x1.c
> index a02dbe900b8..bc42506c65e 100644
> --- a/drivers/net/phy/micrel_ksz90x1.c
> +++ b/drivers/net/phy/micrel_ksz90x1.c
> @@ -336,6 +336,7 @@ static int ksz9031_phy_extwrite(struct phy_device *phydev, int addr,
>   
>   static int ksz9031_config(struct phy_device *phydev)
>   {
> +	unsigned int features = phydev->drv->features;

It's a u32 member, so we can simply use a u32 for the local variable.

This will be overshadowed by unsigned features in the if block, just 
remove the overshadowing variable and features = phydev->drv->features; 
in the if block since you'll already have set it.

>   	int ret;
>   
>   	ret = ksz9031_of_config(phydev);
> @@ -371,7 +372,22 @@ static int ksz9031_config(struct phy_device *phydev)
>   		return 0;
>   	}
>   
> -	return genphy_config(phydev);
> +	/* Silicon Errata Sheet (DS80000691D or DS80000692D):
> +	 * Whenever the device's Asymmetric Pause capability is set to 1,
> +	 * link-up may fail after a link-up to link-down transition.
> +	 *
> +	 * Workaround:
> +	 * Do not enable the Asymmetric Pause capability bit.
> +	 */
> +	features &= ~ADVERTISE_PAUSE_ASYM;
> +	/* update feature support and forward to advertised features */
> +	phydev->supported = features;
> +	phydev->advertising = phydev->supported;
> +
> +	/* genphy_restart_aneg called from genphy_config_aneg */
> +	return genphy_config_aneg(phydev);
> +
> +	return 0;

Don't need the return 0 here as it won't be reached.

Is this errata only applicable if 1000BASE-T is supported? I couldn't 
find that in the doc but maybe I misread. In which case, we need the 
exact same logic in the if (env_get("disable_giga")) section I think?

Cheers,
Quentin