Linuxppc-embedded Digest, Vol 35, Issue 33

suresh suresh sureshtang at
Tue Jul 17 15:59:04 EST 2007


MPC8280 has internal memory space which contains Dualport(Dp) RAM. In the
DpRAM we allocate some tables and these has to store pointer of the buffers
which are allocated in external memory. Core will use this pointer to access
the buffers, basically these buffers are used for DMA.

Using IMMR register we can get physical address of the internal memory. Now
can I store the address return by the kmalloc() function? or I should
convert it into physical?

Please help me how to resove this address translation.


On 7/16/07, Scott Wood <scottwood at> wrote:
> Siva Prasad wrote:
> > It returns kernel virtual address. If you use this buffer space for DMA,
> > please use appropriate flags. You may use __pa(address) or
> > virt_to_phys() to convert virtual to physical.
> No, you may not -- physical and DMA addresses are not always identical.
>   Use the DMA mapping API.
> -Scott
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