> 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? Jocke ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
