[linuxsh-dev] mmap/ remap_page_range problem with SH3 big endian

[alain v. <av...@ya...>]

Hello guys,

well actually I don't know if the problem comes from
SH3 or not but I thought it's a good idea to ask you.

I got problems while using remap_page_range with
mmap/nopage handler. Let me try to describe you what
I'm trying to achieve. I got a custom video card which
has his video memory paged (need to set video card
registers in order to get an area of this memory
directly accessible to the SH3 from address
0xa8000000). Since I need to make this memory
accessible (in a linear way .. sorry I forgot to tell
you that it's a framebuffer driver) from userland, I
was trying to achieve that by using nopage handler
with remap_page_range function.

My nopage function looks like this:

struct page* my_nopage(struct vm_area_struct *vma,
unsigned long address, int no_share)
{
  pgd_t *pgd;
  pmd_t *pmd;
  pte_t *pte;
  unsigned long phys_add;

  /* Set register of the video card to make an area of
the video memory accessible from the SH3 */
  { .... }

  /* Calculate the physical memory address */
  phys_add = {.....}

  /* FIXME ... is it useful in something ??? */
  /* Pages shouldn't be cached */
  vma->vm_page_prot =
pgprot_noncached(vma->vm_page_prot);

  remap_page_range(address & PAGE_MASK, phys_add,
PAGE_SIZE, vma->vm_page_prot);

  pgd = pgd_offset(current->mm, address);
  pmd = pmd_offset(pgd, address);
  pte = pte_offset(pmd, address);

  return pte_page(*pte);
}

The mmap function doesn't do actually to many things
except set the nopage handler.
Everything is done in the nopage handler.

From user space, when I mmap the framebuffer, I can
access to the video memory
...... ONCE. I mean, the mmap function will return a
pointer, using this pointer
I'll be able to read/write into the video memory. For
example I can set all bytes
of the video memory from 0 the end once (lot of nopage
handler will be called)
but then if I try to set once again, the nopage
handler will never be called again.

Well, once again, I don't know if it's a problem due
to the SH or just some 
misunderstanding on the way to use remap_page_range; I
was hoping someone could
confirm this to me, and hopefully tell me what is
wrong.
I hope it's not too difficult to understand my saying.

Sincerely,
Alain Volmat

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