Memory map

Memory map

[Konstantin Sabodash]

Hello TWG - pat, mark & steve.

I've seen your post to linuxppc-embedded@lists.linuxppc.org  regarding
memory access  from Linux.
Your code works fine.

 "paddr2 = mmap(0,size,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0x50000000);"

But  page size is 1K and their start addresses  appears in address
space  with increment 0x1000.
So if I put 0x50000400 address it give me segmentation fault. It works
fine in region 0x50000000 ...  0x500003ff  next 0x50001000 ...
0x500103ff and so on.
Question : how can we increase page size to eliminate these holes.
Thanks in advance.

--
Konstantin Sabodash


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Re: Memory map

[Dan Malek]

Konstantin Sabodash wrote:

>  "paddr2 = mmap(0,size,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0x50000000);"
>
> But  page size is 1K and their start addresses  appears in address
> space  with increment 0x1000.

No, the Linux page size is 4K.

> So if I put 0x50000400 address it give me segmentation fault. It works
> fine in region 0x50000000 ...  0x500003ff  next 0x50001000 ...
> 0x500103ff and so on.
> Question : how can we increase page size to eliminate these holes.

Fix your hardware.  I don't know what "size" is in your mmap() example,
but just because you map a large space doesn't mean you necessarily have
access to all of it.   If the underlying hardware doesn't respond to
the access, you will get a bus timeout error which is reported to your
program as a segmentation violation (or bus fault violation depending
upon how we map the error today).  It looks to me like your hardware
responds to the first 1K of a selected address space, and the memory
controller is programmed to wrap this on 4K boundaries.

What kind of system is this?  What kind of device is mapped to this
address?


	-- Dan

--

	I like MMUs because I don't have a real life.

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IBM Walnut 405GP eval board

[Tom Shaver]

Would anyone happen to know where I could pick one of these up? We've
contacted Avnet and Arrow. Avnet has quoted us 90-120 days lead time, we're
still waiting on Arrow. It seems to me IBM would be more interested in
getting eval systems into engineers hands.

Tom Shaver
Electrical Engineer
Planning Systems Inc.
21294 Johnson Rd
Long Beach, MS 39560
228-863-0007 x121
228-863-0281 Fax


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Re: IBM Walnut 405GP eval board

[Frank Rowand]

Tom Shaver wrote:
>
> Would anyone happen to know where I could pick one of these up? We've
> contacted Avnet and Arrow. Avnet has quoted us 90-120 days lead time, we're
> still waiting on Arrow. It seems to me IBM would be more interested in
> getting eval systems into engineers hands.
>
> Tom Shaver
> Electrical Engineer
> Planning Systems Inc.
> 21294 Johnson Rd
> Long Beach, MS 39560
> 228-863-0007 x121
> 228-863-0281 Fax

You might try contacting one the of IBM regional sales offices. Look at
http://www.chips.ibm.com/support/howtobuy.html for contact info.

I haven't actually tried ordering this way, please let us know if you
get a better lead time from IBM.

-Frank
--
Frank Rowand <frank_rowand@mvista.com>
MontaVista Software, Inc

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