[ECOS] Memory mapping of PCI device memory - PC platform

Hugo Tyson hmt@cygnus.co.uk
Fri Aug 18 05:00:00 GMT 2000


andrew.lunn@ascom.ch (Andrew Lunn) writes:
> > > So there is nothing special to do with eCos when we map memory from a PCI
> > > device, right ?
> > 
> > Not as far as I am aware.
> 
> When we do this for the ebsa285 you have to ensure the MMU is set up
> correctly so that it does not cache or use a write buffer when access
> the PCI memory. There is probably some equivelent setting required in
> the MMU for the i386. Something to check anyway.

Correct.

BTW, for anoncvs fans, soon you'll be getting releases which automatically
allocate all "spare" memory to the heap (as in malloc()) on lots of
platforms.  You have to use the GUI MLT or edit nasty linker files to
prevent this.  The EBSA285 has an explicit and fairly hacky workaround, to
let PCI work,installed in the .ldi files.

We're working on a nicer solution, but for now beware on other platforms,
you may find your PCI area, for example, in memory that you *know* is not
being used, scribbled over by the heap, unless you take action to prevent
it, by editting the .ldi files or using the MLT.

Just in case, this might save someone some debug time...

	- Huge


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