From: Timur Tabi <timur@xxxxxxxxxxxxxx> Date: Thu, 1 Jun 2017 16:08:13 -0500 > Use software polling (PHY_POLL) to check for link state changes instead > of relying on the EMAC's hardware polling feature. Some PHY drivers > are unable to get a functioning link because the HW polling is not > robust enough. > > The EMAC is able to poll the PHY on the MDIO bus looking for link state > changes (via the Link Status bit in the Status Register at address 0x1). > When the link state changes, the EMAC triggers an interrupt and tells the > driver what the new state is. The feature eliminates the need for > software to poll the MDIO bus. > > Unfortunately, this feature is incompatible with phylib, because it > ignores everything that the PHY core and PHY drivers are trying to do. > In particular: > > 1. It assumes a compatible register set, so PHYs with different registers > may not work. > > 2. It doesn't allow for hardware errata that have work-arounds implemented > in the PHY driver. > > 3. It doesn't support multiple register pages. If the PHY core switches > the register set to another page, the EMAC won't know the page has > changed and will still attempt to read the same PHY register. > > 4. It only checks the copper side of the link, not the SGMII side. Some > PHY drivers (e.g. at803x) may also check the SGMII side, and > report the link as not ready during autonegotiation if the SGMII link > is still down. Phylib then waits for another interrupt to query > the PHY again, but the EMAC won't send another interrupt because it > thinks the link is up. > > Cc: stable@xxxxxxxxxxxxxxx # 4.11.x > Tested-by: Manoj Iyer <manoj.iyer@xxxxxxxxxxxxx> > Signed-off-by: Timur Tabi <timur@xxxxxxxxxxxxxx> Applied, thanks.