__pa giving strange phys address on PPC

__pa giving strange phys address on PPC

[dibacco]

Hi all,

I'm using a linux 2.6.19 (from Denx ELDK) on a PPC MPC880. In a driver (t=
hat uses TDM channels) I have some calls to __pa to get the physical addr=
ess corresponding to a virtual address. The physical address returned by =
__pa is higher than the maximum physical memory I have on the board. This=
 result make my driver hang. The driver I'm trying to use was written for=
 a 2.4 kernel and I'm wondering if I have to replace the calls to __pa wi=
th some other API/MACRO.

Thank you in advance.

Re: __pa giving strange phys address on PPC

[Benjamin Herrenschmidt]

On Wed, 2009-01-07 at 21:59 +0100, dibacco@libero.it wrote:
> Hi all,
> 
> I'm using a linux 2.6.19 (from Denx ELDK) on a PPC MPC880. In a driver
> (that uses TDM channels) I have some calls to __pa to get the physical
> address corresponding to a virtual address. The physical address
> returned by __pa is higher than the maximum physical memory I have on
> the board. This result make my driver hang. The driver I'm trying to
> use was written for a 2.4 kernel and I'm wondering if I have to
> replace the calls to __pa with some other API/MACRO.

__pa can only be used on memory coming from the kernel linear mapping.

You probably need to change your driver to use the proper DMA mapping
APIs instead

Cheers,
Ben.

Re: __pa giving strange phys address on PPC

[Josh Boyer]

On Wed, Jan 07, 2009 at 09:59:36PM +0100, dibacco@libero.it wrote:
>Hi all,
>
>I'm using a linux 2.6.19 (from Denx ELDK) on a PPC MPC880. In a driver (that uses TDM channels) I have some calls to __pa to get the physical address corresponding to a virtual address. The physical address returned by __pa is higher than the maximum physical memory I have on the board. This result make my driver hang. The driver I'm trying to use was written for a 2.4 kernel and I'm wondering if I have to replace the calls to __pa with some other API/MACRO.
>
>Thank you in advance.

If you're calling it on an ioremapped address, that won't work.
Those come out of vmalloc space.

Just store the physical address somewhere if you really need it.

josh

Re: __pa giving strange phys address on PPC

[dibacco]

I used __pa on the result of an uncached_mem_alloc. 
Furthermore __pa should work on the return of a kmalloc?

Thank you.

Re: __pa giving strange phys address on PPC

[Benjamin Herrenschmidt]

On Wed, 2009-01-07 at 22:11 +0100, dibacco@libero.it wrote:
> I used __pa on the result of an uncached_mem_alloc. 

No idea what uncached_mem_alloc() is but if that uses the consistent
memory stuff it won't work with __pa.

> Furthermore __pa should work on the return of a kmalloc?

Yes. But don't use that, just use the dma allocation/mapping functions
instead, they return to you both the pa and the dma_addr_t. This is
better for -many- reasons.

Cheers,
Ben.