Re: [PATCH v2 03/10] phy: rockchip: naneng- combphy: add SGMII MAC selection for RK3568

On August 2, 2026 4:58:39 AM GMT+08:00, Andrew Lunn <andrew@lunn=2Ech> wrot=
e:
>On Sat, Aug 01, 2026 at 10:22:27PM +0800, Coia Prant wrote:
>> On RK3568, the SGMII interface can be routed to either GMAC0 or
>> GMAC1 via the GRF register pipe_sgmii_mac_sel=2E
>>=20
>> Add support for this selection by introducing
>> the "rockchip,sgmii-mac-sel" DT property=2E
>>=20
>> The hardware reset value is GMAC1 (1)=2E If the property is set to 0,
>> the driver routes SGMII to GMAC0; if set to 1 (or omitted), it
>> remains at GMAC1=2E
>>=20
>> This is necessary for boards such as the Ariaboard Photonicat, which
>> uses the SGMII interface connected to GMAC0=2E
>
>If SGMII is not selected, what MII is used? RGMII?
>
>Can this setting be implied from phy-mode?
>
>	Andrew

Hi Andrew,

If phy-mode is not "sgmii" (e=2Eg=2E, "rgmii" or "rmii"), the GMAC works i=
n
the corresponding mode and this register is not touched=2E The reset
default (GMAC1) remains, but it has no effect in non-SGMII modes because
the register only controls SGMII signal routing=2E

Regarding inference from phy-mode: phy-mode =3D "sgmii" only tells the MAC
driver that the interface is SGMII=2E It does not specify whether the
SGMII signals are physically routed to GMAC0 or GMAC1 on the board=2E
That routing is a board-level decision and cannot be derived from any
other DT property=2E

Also, the PHY (Naneng Combo PHY) is initialized by the XPCS glue driver
(pcs-xpcs-rk), not by the GMAC driver=2E The PHY driver has no way to know
which GMAC is using it=2E Making the PHY aware of the MAC ID would require
significant changes to the PHY layer, which is out of scope
for this series=2E

Therefore, an explicit DT property is the cleanest and most maintainable
way to describe this hardware routing=2E

Thanks,
Coia