On Tue, Jul 10, 2012 at 10:03 PM, 弋天 卜 <[email protected]> wrote:
>
>
> 在 2012-7-10，17:16，"Prabhu nath" < <[email protected]>
> [email protected]> 写道：
>
> Thanks for your reply. Plz see inline
>
> On Tue, Jul 10, 2012 at 11:17 AM, Philipp Ittershagen
> <<[email protected]><[email protected]>
> [email protected]> wrote:
>
>> Hi Prabhu,
>>
>> On Tue, Jul 10, 2012 at 6:56 AM, Prabhu nath <
>> <[email protected]><[email protected]>
>> [email protected]> wrote:
>> > 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
>> > virtual address range 0xF0008000 to 0xF0008FFF.
>>
>> I don't think this is possible, because these virtual address ranges
>> are handled by the kernel VMA system and are allocated dynamically, so
>> that is not just a bitmask or something to change.
>>
>> > 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
>> > to a fixed range of 128 MB from 0xC8000000 to 0xCFFFFFFF
>>
>> You could change PAGE_OFFSET. From [1]:
>>
>>
>> PHYS_OFFSET
>> Physical start address of the first bank of RAM.
>>
>> PAGE_OFFSET
>> Virtual start address of the first bank of RAM. During the kernel
>> boot phase, virtual address PAGE_OFFSET will be mapped to physical
>> address PHYS_OFFSET, along with any other mappings you supply.
>> This should be the same value as TASK_SIZE.
>>
>>
>> But I'm curious: Why do you want to change it?
>>
>
> Just wanted to have a constant mapping from PA to VA of devices and
> wanted to have a separate region for vmalloc.
>
>>
>>
> what do you mean constant?
> After mapping, it is constant.
> Before mapping, it is constant for
> Low memory region, but is not
> Constant for vmalloc region.
>
I mean fixed/static mapping rather than kernel allocating kernel virtual
address dynamically.
>
> Vmalloc region is separate in default.
> Your change doesn't make any sense.
>
You mean ioremap(...) will not map the physical address of the device
into vmalloc region ?
>
> The most difficult thing for you is
> To make sure what do you want to
> Do really. Please give detail demand.
>
My requirement is very simple. I have designed a layout showing mapping
of physical address to kernel virtual address. I also want to implement in
the same way.
1. Low mem region - which is already fixed by the kernel based on the
memory size.
2. Vmalloc region which can be fixed as per your previous mail
3. Also have a fixed mapping of device physical address by
ioremap_page_range(...)
I think I got what I needed. Thank you all very much for your valuable
time.
>
>
>
>> Greetings,
>>
>> Philipp
>>
>>
>> [1]:
>> <http://www.kernelport.org/defines.html><http://www.kernelport.org/defines.html>
>> http://www.kernelport.org/defines.html
>>
>
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