[parisc-linux-cvs] U bit and memory mapped IO

John Marvin jsm@udlkern.fc.hp.com
Sun, 3 Mar 2002 23:04:07 -0700 (MST)

> Thomas Bogendoerfer wrote:
> >       arch/parisc/kernel: entry.S
> >
> > Log message:
> > set U bit in TLB for uncached memory. This is needed for mmaped IO space
> > (framebuffers)
> I'm surprised this is needed for "F-space". (ie 0xf...).
> My understanding is the CPU is hardcoded to not cache F-space.
> I thought this was true of both PA1.1 and PA2.0 machines.
> Can anyone confirm/deny this?

U bit is only necessary for F space access on PCXL2. It is not necessary
on any other processor.

John Marvin