Thread (10 messages) 10 messages, 4 authors, 2012-07-11

Mapping of Device Physical Address to Kernel Virtual address

From: Prabhu nath <hidden>
Date: 2012-07-10 09:00:56

Thanks for your reply. Plz see inline

On Tue, Jul 10, 2012 at 11:50 AM, Dave Hylands [off-list ref] wrote:
Hi Prabhu,

On Mon, Jul 9, 2012 at 9:56 PM, Prabhu nath [off-list ref] wrote:
quoted
Dear All,

                   Is it possible to map a physical address of a device
to a
quoted
known Kernel virtual address. I know about ioremap_xxx (...).
which will map a physical address of a device to a kernel virtual address
allocated by ioremap_xxx(...).

For E.g. I have a device whose physical address range is 0x80008000 to
0x80008FFF.
             Is it possible to map this device physical address to a
known
quoted
virtual address range 0xF0008000 to 0xF0008FFF.
About the only way to do this is to use static mappings. I was under
the impression that static mappings are on the way out, and that
dynamic mappings are required when using device tree.

An example of using static mappings can be found here:

http://lxr.linux.no/linux+v3.4.4/arch/arm/mach-integrator/integrator_ap.c#L88

   In this file, how did they mark IO_BASE. Is the allocator not aware of
this region in the kernel virtual address space. ?
quoted
My hardware configuration has 128 MB of system RAM which will have been
MAPPED to the Kernel virtual address from 0xC0000000 to 0xC7FFFFFF

Also is it possible to configure the vmalloc kernel virtual address
region
quoted
to a fixed range of 128 MB from 0xC8000000 to 0xCFFFFFFF
I believe that you can only control the vmalloc start by controlling
the amount of SDRAM that you have.

--
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com
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