__pa(dma_alloc_coherent()) doesn't give physical address

__pa(dma_alloc_coherent()) doesn't give physical address

[DI BACCO ANTONIO - technolabs]

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dma_alloc_coherent gives a kernel virtual address as a return address,
applying __pa I expected a physical address.
It doesn't happen, I receive an address far beyond my 16 MB ram.
Applying virt_to_bus doesn't give a physical address too.
OK, you can resort to dma_addr_t parameter of dma_alloc_coherent but is
there a reason for __pa not working on a kernel virtual address?
 
 
 
Bye,
Antonio.

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Re: __pa(dma_alloc_coherent()) doesn't give physical address

[Dan Malek]

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On Feb 26, 2007, at 10:54 AM, DI BACCO ANTONIO - technolabs wrote:

> dma_alloc_coherent gives a kernel virtual address as a return address,

....and more.  Everything you need.
Read Documentation/DMA-API.txt

> applying __pa I expected a physical address.

You don't need to (and shouldn't) do this.


	-- Dan


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