The Did you monitor the 30th bit of PIB->gpif_config? This is where you monitor whether PP mode is enabled or not. You have mentioned in your post that you looked at PIB->config.
I had not been checking the value of that register, but I changed its value to one and I still see the same behavior.
I'm facing the same problem and would like a fix for this. Although I am able to program the PP_MMIO_ADDR register, but whenever I want to do I R/W, I'm unable to change the PP_MMIO register to actually perform the R/W. I always read 0.
My register value for PIB_CONFIG is 0xC8000000.
My register value for GPIF_CONFIG is 0xC0000A12.
Please note that I'm trying to access the MMIO space from an external processor via the p-port. Is there a special way to do this ?