[alsa-devel] Getting physical address of the DMA buffer

Pharaoh . pharaoh137 at gmail.com
Wed Jun 27 13:34:46 CEST 2007

Okay got it now. The omap I am using has a ARM926 which has a MMU. So
I shouldn't be using SNDRV_DMA_TYPE_CONTINUOUS. I will try to allocate
using other methods.

On 6/27/07, Clemens Ladisch <cladisch at fastmail.net> wrote:
> Pharaoh . wrote:
> > On 6/27/07, Clemens Ladisch <cladisch at fastmail.net> wrote:
> > > SNDRV_DMA_TYPE_CONTINUOUS is for a buffer that cannot be accessed
> > > over DMA.
> > >
> > > What kind of bus does your hardware use, and how would you
> > > allocate memory for it?
> >
> > Continuous buffers unrelated to the bus type can be allocated using
> > SNDRV_DMA_TYPE_CONTINUOUS right? I am referring a standard driver from
> > omap source tree, and the buffer allocation functions I have copied
> > from there and they should be same for the range of OMAPs since the
> > dma handling is same for them.
> I don't know anything about OMAP.
> If the processor doesn't use a MMU, then the memory addresses as seen
> by the CPU are the same as those used by a device using DMA.  In that
> case, you could use SNDRV_DMA_TYPE_CONTINUOUS and the correct address
> would be available as runtime->dma_area.
> Clemens

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