At Wed, 14 Nov 2007 17:43:21 +0530, Pharaoh . wrote: > > On Nov 14, 2007 1:44 PM, Takashi Iwai <tiwai@xxxxxxx> 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 > > based > > > 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 > > passing > > > my device pointer i.e. card->dev after > > > correctly populating it but I get an error as 'DMA coherent mask in not > > set' > > > 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. > > > > > > Takashi > > > > 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 > rmmod time. > > 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 > be done? Unfortuantely, no other way, so far. It's the only way that a driver can do -- keeping the large chunk as long as it needs. Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
