uncached user space mapping with mmap() ???

Steven Scholz steven.scholz at imc-berlin.de
Fri Mar 5 00:51:32 EST 2004

Hi there,

I am trying to access a hardware timer implemented in an FPGA from
user space. I implemented a simple mmap() functionality (taken from
Runbini's Linux Device Driver)

int simple_remap_mmap(struct file *filp, struct vm_area_struct *vma)
      unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;

      if (offset >= __pa(high_memory) || (filp->f_flags & O_SYNC)) {
          vma->vm_flags |= VM_IO;
      vma->vm_flags |= VM_RESERVED;

      if (remap_page_range(vma->vm_start, offset,
	vma->vm_end-vma->vm_start, vma->vm_page_prot))
	        return -EAGAIN;

      return 0;

I just learned that

 > getting an uncached user space mapping is architecture dependent.
 > On ARM, however, passing pgprot_noncached(vma->vm_page_prot) to
 > remap_page_range() will alter the page protections such that the
 > mapping will be uncached.

How could I do this on an MPC8xx?

Thanks a million!

Steven Scholz

imc Measurement & Control               imc Meßsysteme GmbH
Voltastr. 5                             Voltastr. 5
13355 Berlin                            13355 Berlin
Germany                                 Deutschland

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