With the help from Attila, I got the latest tdfx framebuffer driver
working on my NEC DDB5476 board. I have console working based on this
However, when I try to mmap frame buffer into user land, the mapping is
succesful, but trying to read the buffer causes a bus error.
I tried to trace the kernel using gdb. fb_mmap() seems to do the right
1) it calls fb->fb_get_fix() to get the buffer address, size, etc. The
values all look fine. The address is physical address, pointing a
mapped PCI memory block. I verified that I can access that address in
2) for MIPS, fb_mmap() turns off CACHE bit for the page.
I would imagine when the app tries to read the buffer, a TLB miss is
generated. TLB refill routine probably sets up the right TLB entry, and
the app will try to read again, and get the content. I really can't
think of where the Bus error might occur.
Does anybody have a clue here? Thanks a lot.