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. Does this make any sense to anyone? I can prepare a patch if somebody is interested to try it on their 8xx CPU. Jocke ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
