Re: [PATCH net-next] net: phy: realtek: support MDI swapping for RTL8226-CG

[Paolo Abeni <pabeni@redhat.com>]

On 3/22/26 8:31 PM, Jan Hoffmann wrote:
> Add support for configuring swapping of MDI pairs (ABCD->DCBA) when the
> property "enet-phy-pair-order" is specified.
> 
> Unfortunately, no documentation about this feature is available, so the
> configuration involves magic values. As it is unknown whether the
> patching step can be safely reversed, only enabling MDI swapping is
> supported.

Still using human readable macros would improve readability, reduce the
change of c&p mistakes. I suggest you use chose some more explanatory
names at least for the more used values.

> Some other Realtek PHYs also support similar mechanisms:
> 
> - RTL8221B-VB-CG allows to configure MDI swapping via the same register,
>   but does not need the additional patching step. However, it is unclear
>   whether a driver implementation for that PHY is necessary, as it is
>   known to support configuration via strapping pins (which is working
>   fine at least in Zyxel XGS1210-12 rev B1).
> 
> - The patching step seems to match the one for the integrated PHYs of
>   some Realtek PCIe/USB NICs (see for example the r8152 driver).
> 
> For now, only implement this for the RTL8226-CG PHY, where it is needed
> for the switches Zyxel XGS1010-12 rev A1 and XGS1210-12 rev A1.
> 
> Signed-off-by: Jan Hoffmann <jan@3e8.eu>
> ---
>  drivers/net/phy/realtek/realtek_main.c | 142 ++++++++++++++++++++++++-
>  1 file changed, 141 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/phy/realtek/realtek_main.c b/drivers/net/phy/realtek/realtek_main.c
> index 023e47ad605b..2472f54502bd 100644
> --- a/drivers/net/phy/realtek/realtek_main.c
> +++ b/drivers/net/phy/realtek/realtek_main.c
> @@ -1447,6 +1447,146 @@ static unsigned int rtl822x_inband_caps(struct phy_device *phydev,
>  	}
>  }
>  
> +static int rtl8226_set_mdi_swap(struct phy_device *phydev, bool swap_enable)
> +{
> +	u16 val = swap_enable ? BIT(5) : 0;
> +
> +	return phy_modify_mmd(phydev, MDIO_MMD_VEND1, 0x6a21, BIT(5), val);
> +}
> +
> +static int rtl8226_patch_mdi_swap(struct phy_device *phydev)
> +{
> +	u16 values[4];
> +	int ret;
> +
> +	ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, 0xd068);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (!(ret & BIT(1))) {
> +		/* already swapped */
> +		return 0;
> +	}
> +
> +	ret = phy_modify_mmd(phydev, MDIO_MMD_VEND2, 0xd068, 0x7, 0x1);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* swap adccal_offset */
> +
> +	for (int i = 0; i < 4; i++) {
> +		ret = phy_modify_mmd(phydev, MDIO_MMD_VEND2, 0xd068, 0x3 << 3, i << 3);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, 0xd06a);
> +		if (ret < 0)
> +			return ret;
> +
> +		values[i] = ret;
> +	}
> +
> +	for (int i = 0; i < 4; i++) {
> +		ret = phy_modify_mmd(phydev, MDIO_MMD_VEND2, 0xd068, 0x3 << 3, i << 3);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, 0xd06a, values[3 - i]);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	/* swap rg_lpf_cap_xg */
> +
> +	ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, 0xbd5a);
> +	if (ret < 0)
> +		return ret;
> +
> +	values[0] = ret & 0x1f;
> +	values[1] = (ret >> 8) & 0x1f;
> +
> +	ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, 0xbd5c);
> +	if (ret < 0)
> +		return ret;
> +
> +	values[2] = ret & 0x1f;
> +	values[3] = (ret >> 8) & 0x1f;
> +
> +	ret = phy_modify_mmd(phydev, MDIO_MMD_VEND2, 0xbd5a, 0x1f1f,
> +			     values[3] | (values[2] << 8));

It looks like there are a few FIELD_GET/FIELD_PREP use cases above
(which will work better together with define for relevant values).

/P