On 3/18/2021 6:25 AM, Heiner Kallweit wrote: > On 18.03.2021 10:09, Wong Vee Khee wrote: >> When using Clause-22 to probe for PHY devices such as the Marvell >> 88E2110, PHY ID with value 0 is read from the MII PHYID registers >> which caused the PHY framework failed to attach the Marvell PHY >> driver. >> >> Fixed this by adding a check of PHY ID equals to all zeroes. >> > > I was wondering whether we have, and may break, use cases where a PHY, > for whatever reason, reports PHY ID 0, but works with the genphy > driver. And indeed in swphy_read_reg() we return PHY ID 0, therefore > the patch may break the fixed phy. > Having said that I think your patch is ok, but we need a change of > the PHY ID reported by swphy_read_reg() first. > At a first glance changing the PHY ID to 0x00000001 in swphy_read_reg() > should be sufficient. This value shouldn't collide with any real world > PHY ID. It most likely would not, but it could be considered an ABI breakage, unless we filter out what we report to user-space via SIOGCMIIREG and /sys/class/mdio_bus/*/*/phy_id Ideally we would have assigned an unique PHY OUI to the fixed PHY but that would have required registering Linux as a vendor, and the process is not entirely clear to me about how to go about doing that. -- Florian
