[alsa-devel] Query regarding snd_pcm_lib_preallocate_pages_for_all()
pharaoh137 at gmail.com
Wed Nov 14 13:13:21 CET 2007
On Nov 14, 2007 1:44 PM, Takashi Iwai <tiwai at suse.de> wrote:
> At Wed, 14 Nov 2007 00:12:07 +0530,
> Pharaoh . wrote:
> > Hi,
> > I am trying to use snd_pcm_lib_preallocate_pages_for_all() on an arm
> > platform for preallocating the DMA buffer.
> > I am using it as
> > snd_pcm_lib_preallocate_pages_for_all(pcm,
> > SNDRV_DMA_TYPE_DEV,
> > NULL,
> > 64 * 1024, 64 * 1024);
> > since I dont know what should be passed as the 3'rd param. I tried
> > my device pointer i.e. card->dev after
> > correctly populating it but I get an error as 'DMA coherent mask in not
> > and buffer is not allocated.
> For ARM, avoid the present buffer-preallocation and mmap functions in
> ALSA core. Instead you can allocate the buffers directly via normal
> dma_alloc_coherent() in your driver. And, mmap it via
> dma_mmap_coherent() by defining the own mmap callback for PCM ops.
> See other arm/* drivers for rerecence.
Yes, I am using my own buffer preallocation scheme now. I allocate a 128K
buffer using dma_alloc_coherent in probe and free it only in remove i.e. at
I dont think keeping a huge buffer like this till driver removal is a good
idea but when I allocate/deallocate it in hw_params/hw_free respectively, it
is causing fragmentation and sometimes the allocation fails. Do you think
anything better can
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