Ioremap related concern ...

Ioremap related concern ...

[Misbah khan]

Hi all,

i am facing a problem regarding the usage of ioremap function which is
described as:-

1) I am remaping the SDRAM memory into three continews buffer as 
	ptr1 = (unsigned int *)ioremap(0x0001000,0x1000);
	ptr2 = (unsigned int *)ioremap(0x0002000,0x1000);
	ptr3 = (unsigned int *)ioremap(0x0003000,0x1000);

I am filling the data into the SDRAM buffer using these remap pointers 

2)  SDRAM is mmaped to user space into a buffer as 
	struct sdram_buf
	{
		unsigned int buf[4096];

	};
	struct sdram_buf sdram_buf_obj[3];

The mapping looks correct but it doesent work ... :(

	If is do the ioremap like this it works 
	
	ptr1 = (unsigned int *)ioremap(0x0001000,(0x1000 * 4));
	ptr2 = (unsigned int *)ioremap(0x0002000,(0x1000 * 4));
	ptr3 = (unsigned int *)ioremap(0x0003000,(0x1000 * 4));

	Doing this actually takes more space into the ram memory hence for mapping 
	1 M of Ram memeoy it actually takes 4 MB practically.

Can any one point out the mistake or suggest something ...
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Re: Ioremap related concern ...

[Grant Likely]

On Wed, Sep 17, 2008 at 9:43 PM, Misbah khan <misbah_khan@engineer.com> wrote:
>
> Hi all,
>
> i am facing a problem regarding the usage of ioremap function which is
> described as:-
>
> 1) I am remaping the SDRAM memory into three continews buffer as
>        ptr1 = (unsigned int *)ioremap(0x0001000,0x1000);
>        ptr2 = (unsigned int *)ioremap(0x0002000,0x1000);
>        ptr3 = (unsigned int *)ioremap(0x0003000,0x1000);

Ah, this doesn't work.  You can't just choose a region of ram and
ioremap it.  Besides, the base of RAM is already used by the interrupt
vectors.

If you need to allocate a region for DMA buffers, then take a look at
dma_alloc_coherent().  If you just need to allocate some buffers, then
just use kzalloc().

g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.