From: Vladimir Oltean <vladimir.oltean@xxxxxxx> The "reverse RMII" protocol name is a personal invention, derived from "reverse MII". Just like MII, RMII is an asymmetric protocol in that a PHY behaves differently than a MAC. In the case of RMII, for example: - the 50 MHz clock signals are either driven by the MAC or by an external oscillator (but never by the PHY). - the PHY can transmit extra in-band control symbols via RXD[1:0] which the MAC is supposed to understand, but a PHY isn't. The "reverse MII" protocol is not standardized either, except for this web document: https://www.eetimes.com/reverse-media-independent-interface-revmii-block-architecture/# In short, it means that the Ethernet controller speaks the 4-bit data parallel protocol from the perspective of a PHY (it acts like a PHY). This might mean that it implements clause 22 compatible registers, although that is optional - the important bit is that its pins can be connected to an MII MAC and it will 'just work'. In this discussion thread: https://lore.kernel.org/netdev/20210201214515.cx6ivvme2tlquge2@skbuf/ we agreed that it would be an abuse of terms to use the "RevMII" name for anything than the 4-bit parallel MII protocol. But since all the same concepts can be applied to the 2-bit Reduced MII protocol as well, here we are introducing a "Reverse RMII" protocol. This means: "behave like an RMII PHY". Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx> --- .../devicetree/bindings/net/ethernet-controller.yaml | 1 + include/linux/phy.h | 4 ++++ 2 files changed, 5 insertions(+) diff --git a/Documentation/devicetree/bindings/net/ethernet-controller.yaml b/Documentation/devicetree/bindings/net/ethernet-controller.yaml index e8f04687a3e0..d97b561003ed 100644 --- a/Documentation/devicetree/bindings/net/ethernet-controller.yaml +++ b/Documentation/devicetree/bindings/net/ethernet-controller.yaml @@ -68,6 +68,7 @@ properties: - tbi - rev-mii - rmii + - rev-rmii # RX and TX delays are added by the MAC when required - rgmii diff --git a/include/linux/phy.h b/include/linux/phy.h index 852743f07e3e..ed332ac92e25 100644 --- a/include/linux/phy.h +++ b/include/linux/phy.h @@ -93,6 +93,7 @@ extern const int phy_10gbit_features_array[1]; * @PHY_INTERFACE_MODE_TBI: Ten Bit Interface * @PHY_INTERFACE_MODE_REVMII: Reverse Media Independent Interface * @PHY_INTERFACE_MODE_RMII: Reduced Media Independent Interface + * @PHY_INTERFACE_MODE_REVRMII: Reduced Media Independent Interface in PHY role * @PHY_INTERFACE_MODE_RGMII: Reduced gigabit media-independent interface * @PHY_INTERFACE_MODE_RGMII_ID: RGMII with Internal RX+TX delay * @PHY_INTERFACE_MODE_RGMII_RXID: RGMII with Internal RX delay @@ -126,6 +127,7 @@ typedef enum { PHY_INTERFACE_MODE_TBI, PHY_INTERFACE_MODE_REVMII, PHY_INTERFACE_MODE_RMII, + PHY_INTERFACE_MODE_REVRMII, PHY_INTERFACE_MODE_RGMII, PHY_INTERFACE_MODE_RGMII_ID, PHY_INTERFACE_MODE_RGMII_RXID, @@ -185,6 +187,8 @@ static inline const char *phy_modes(phy_interface_t interface) return "rev-mii"; case PHY_INTERFACE_MODE_RMII: return "rmii"; + case PHY_INTERFACE_MODE_REVRMII: + return "rev-rmii"; case PHY_INTERFACE_MODE_RGMII: return "rgmii"; case PHY_INTERFACE_MODE_RGMII_ID: -- 2.25.1
