LinuxPPC-Dev Archive on lore.kernel.org

* MPC5200 mmap, ioremap
From: Kunkel, Ulrich @ 2005-08-22  8:47 UTC (permalink / raw)
  To: 'linuxppc-embedded@ozlabs.org'

[-- Attachment #1: Type: text/plain, Size: 2753 bytes --]

Hello,

I am using a Motorola PPC Hardware (MPC5200) with linux kernel 2.4.25 and 32
MB RAM.

I  would like to map a large contiguous kernel memory buffer (6 MB) into
user space with mmap and remap_page_range. For this action I reserved memory
at the end of the phyiscal memory at boot time. (Kernel boot option mem =12
M) Now, the kernel only knows about 20 MB of memory. The high_memory border
is at 0x1400000 (physical address).

I have to do a ioremap() on the high_memory (0x1400000) to map the high
physical memory into a virtual kernel memory.

ioremap_ptr = ioremap_nocache (__pa(high_memory), 6*1024*1024);  //6 MB

ioremap_ptr is a virtual kernel address.

Now I do a mem_map_reserve () on every page in this memory block.

On the ioremap ptr I do a memset to check the data in user space later.

memset(ioremap_ptr, 0xAB, 6*1024*1024);

With bdi2000 I looked to the memory values at 0x1400000 and everything is
ok, I see 0xABABABAB.

If I do a virt_to_phys() on ioremap_ptr, I get a really strange address. I
expected to get the physical address 0x1400000.

Example:

__pa(high_memory): 0x1400000

ioremap_ptr: 0xc22a4000

virt_to_phys(ioremap_ptr): 0x22a4000

virt_to_bus(ioremap_ptr): 0x22a4000

Now I want to map the buffer into to user space with mmap and
remap_page_range.

static int mmmap (struct file *file, struct vm_area_struct *vma)

{

      unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;

      int error;

      unsigned long start = (unsigned long)vma->vm_start;

      unsigned long size = (unsigned long)(vma->vm_end - vma->vm_start);

      if (offset != 0)

      {

        printk ("rt_iso1394_mmap: invalid offset: must be 0\n");

        return -ENXIO;

      }

if(size == PAGE_ALIGN(6*1024*1024)

{

  start,virt_to_phys(shared_buffer_ptr), size, protect);

  error = remap_page_range (vma->vm_start, 0x1400000 , size, PAGE_SHARED);

  if (error)

   {

     printk ("rt_iso1394_mmap: remap_page_range failed\n");

     return -EAGAIN;

   }

 }

 else

 {

  printk ("rt_iso1394_mmap: invalid mmap size, size is: %d\n", (int) size);

  return -EAGAIN;

  }

      return 0;

}

The function returned with no errors. 

If I call mmap () in user space, the function returnes a virtual user
address. But if do a read on this memory, I don't see the data I have
written in the kernel data block in kernel space. I only get zeros. It seems
that remap_page_range maps a completely different data block.

Are the any ideas to solve the problem? What I am doing wrong? What is
missing? Where ist the problem with the addresses???

Thanks for your help 

Ulrich Kunkel

Hottinger Baldwin Messtechnik GmbH

[-- Attachment #2: Type: text/html, Size: 13418 bytes --]

^ permalink raw reply