> > Hi list > > > > I have been researching why I can't use dcbz and friends on 8xx CPU. > > Till Strauman found out long ago that the dcxx instuctions did not update > > the DAR register and that was the key I needed. > > > > After a lot of testing/reading I found a 2 instruction workaround > > that lets me use dcbz in copy_tofrom_user(). > > I can also used dcbz in a user space app without problems. I even > > removed the TLB change bit hack by Tom Rini and everything works. > > > > By copying the MD_EPN register to the DAR register in the DTLB Miss handler > > just before MD_RPN is written everything just works. The only explanation > > that > > makes sense to me is that the MD_RPN has a undocumented dependency to the > > DAR > > register, the 20 msb of MD_EPN and DAR needs to be the same before MD_RPN > > is written. > > hmm, this is not quite correct. I can copy MD_EPN to DAR after the write to > MD_RPN > and it still works. Seems like DAR must be correct when rfi is executed. I > wonder > why?
hmm, can it be that when you return from the DTLB Miss, you sometimes get an DTLB error immediately and that DTLB Error "inherits" the DAR from the DTLB Miss? I removed the "copy DAR to MD_EPN" part in the DTLB Error handler and my systems runs fine. Jocke ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
