On Fri, 2016-04-29 at 13:00 +0200, Guillermo Rodriguez Garcia wrote: > 2016-04-28 23:09 GMT+02:00 Trent Piepho <tpiepho@xxxxxxxxxxxxxx>: > > > > The first anreg start call will also un-powerdown the PHY if BMCR_PDOWN > > was set. I wonder if that is happening? > > That was a very good hint and it looks like this is exactly what is happening. > > genphy_restart_aneg() clears the BMCR_PDOWN bit and would get the phy > out of powerdown mode. I have added a trace right at the beginning of > genphy_restart_aneg and verified that BMCR_PDOWN bit was set before > genphy_restart_aneg clears it. > > Then, the datasheet for the ksz9031 [1], page 44, says: > > After this bit is changed from '1' to '0', an internal global reset is > automatically generated. Wait a minimum of 1ms before read/write > access to the PHY registers. Mystery solved! > So this seems to be what is causing the problem. At least on the > ksz9031 (don't know about others), a delay of 1ms is required when > coming out of powerdown mode. The kernel will take the phy in/out of powerdown mode as part of the PM suspend/resume calls, which is supported on all micrel phys since 2013. I don't see a delay in the kernel code and wonder why this hasn't been a problem? Might be worth asking on net-dev if this is a known issue with some phys and how it is solved? Maybe it's an undiscovered cause of network flakiness after a resume. > What is the best way to fix this? We can add a 1ms delay in > genphy_restart_aneg (this is probably the easiest, and the delay is > small enough that it shouldn't make a difference for other phys that > might not need it). Or if this is not acceptable, perhaps add a custom > restart_aneg function for the ksz9031. Could add a custom init function that un-powerdowns the phy and does the wait. Or have restart_aneg check if the powerdown bit was set before it clears it, and only delay in that case. Having the un-powerdown in the restart_aneg isn't really the right place for it. If there is no reason the restart aneg, then the phy will not be powered up. _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
