> -----Original Message-----
> From: Andrew Lunn <andrew@xxxxxxx>
> Sent: 2024年8月15日 22:33
> To: Wei Fang <wei.fang@xxxxxxx>
> Cc: davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx;
> pabeni@xxxxxxxxxx; robh@xxxxxxxxxx; krzk+dt@xxxxxxxxxx;
> conor+dt@xxxxxxxxxx; f.fainelli@xxxxxxxxx; hkallweit1@xxxxxxxxx;
> linux@xxxxxxxxxxxxxxx; Andrei Botila (OSS) <andrei.botila@xxxxxxxxxxx>;
> netdev@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH net-next 1/3] dt-bindings: net: tja11xx: use reverse-mode
> to instead of rmii-refclk-in
>
> On Thu, Aug 15, 2024 at 01:51:24PM +0800, Wei Fang wrote:
> > Per the MII and RMII specifications, for the standard RMII mode, the
> > REF_CLK is sourced from MAC to PHY or from an external source.
> > For the standard MII mode, the RX_CLK and TX_CLK are both sourced by
> > the PHY. But for TJA11xx PHYs, they support reverse mode, that is, for
> > revRMII mode, the REF_CLK is output, and for revMII mode, the TX_CLK
> > and RX_CLK are inputs to the PHY.
> > Previously the "nxp,rmii-refclk-in" was added to indicate that in RMII
> > mode, if this property present, REF_CLK is input to the PHY, otherwise
> > it is output. This seems inappropriate now. Firstly, for the standard
> > RMII mode, REF_CLK is originally input, and there is no need to add
> > the "nxp,rmii-refclk-in" property to indicate that REF_CLK is input.
> > Secondly, this property is not generic for TJA PHYs, because it cannot
> > cover the settings of TX_CLK and RX_CLK in MII mode. Therefore, add
> > new property "nxp,reverse-mode" to instead of the "nxp,rmii-refclk-in"
> > property.
>
> Please could you add some justification why using
> PHY_INTERFACE_MODE_REVRMII is not possible.
>
According to the commit message c858d436be8b ("net: phy: introduce
PHY_INTERFACE_MODE_REVRMII"), my understanding is that
PHY_INTERFACE_MODE_REVRMII and PHY_INTERFACE_MODE_REVMII
are used for MAC to MAC connections, which means the MAC behaves
link an RMII/MII PHY. For the MAC to PHY connection, I think these two
macros are not applicable.
Currently PHY_INTERFACE_MODE_REVMII is used in both TJA11xx drivers,
and if my understanding is correct I think they will need to be removed in
the future.
