How to use mtdcr from userland code

[Josh Boyer]

On Tue, 23 Sep 2008 16:41:49 -0500
"Ayman El-Khashab" <AymanE at tanisys.com> wrote:

> Greetings,
> 
> I am developing an app that needs to map pci address space to the PLB on
> the ppc460ex.  From what I gather I need to use the mtcdr
> instruction/macro to configure the PIM0 space.  However, I cannot figure
> out how to use that from userland code.  Is it possible? 

Normally, no.  The mtdcr/mfdcr instructions are privileged
instructions.  On that particular core though, there are userspace dcr
instructions.  They are mtdcrux/mfdcrux instructions documented in the
CPU manual.

You will have to hard code them, as there are no versions of binutils
that I know of that will emit the userspace dcr instructions.

> Can I change the PIM some other way?

Yes, write a proper driver.

josh