On 21-07-20, 15:37, Russell King - ARM Linux admin wrote: > Hi, > > While testing phylink over the weekend, I found it was possible to > cause the mvneta hardware to lockup in various weird and wonderful > ways by switching the interface speed between 1G and 2.5G repeatedly. > It didn't require a rapid switching, but one switch every few seconds. > > Symptoms included one or more of: > - Timeout while trying to stop transmit (seen once) > - 2500BASE-X link negotiation failure (fails to exchange link word.) > - Detects lack of sync, but fails to flag 10ms of sync failure. > - SyncOk bit randomly toggles. > > Once the hardware gets into a "bad" state, trying to recover it by > using the mvneta GMAC port reset fails to resolve the issue. > Disabling the port also fails to recover it. The only way to > recover seemed to be via a reboot. > > Many solutions to solve this were tried in various combinations - > while changing the COMPHY configuration: > - putting the GMAC into reset > - disabling the GMAC port > - augmenting the COMPHY configuration to try to "cleanly" disable > the COMPHY via phy_power_down() and reconfigure it via > phy_power_up(), including resetting parts of the COMPHY and > re-running the RX initialisation. > > None of that worked. It was then discovered from the u-boot sources > that there is an undocumented register that has a lane-specific bit > set at the end of COMPHY initialisation, once the loosely documented > COMPHY setup has completed. > > Experimentation with that showed that if the lane specific bit is > cleared before changing the COMPHY "GEN" configuration, and set > afterwards, mvneta no longer locks up. > > Unfortunately, this undocumented register is not part of the COMPHY > register set that we map - it is located in a region of "System > Registers" which are shared between multiple different devices. > > Who should be responsible for mapping this register (mvneta or > COMPHY) was considered; the register is only present on Armada 38x > systems, and seemingly not on Armada 37x or Armada 37xx systems. > It seems that it is a system-level register. The COMPHYs seem to > be system specific, so let's make it part of the COMPHY. > > With no real information on this register, all we can do is guess > about it's function and how to fit it into the system. Applied 1 & 3, thanks -- ~Vinod
